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1.  Foetal stem cell derivation & characterization for osteogenic lineage 
Background & objectives:
Mesencymal stem cells (MSCs) derived from foetal tissues present a multipotent progenitor cell source for application in tissue engineering and regenerative medicine. The present study was carried out to derive foetal mesenchymal stem cells from ovine source and analyze their differentiation to osteogenic linage to serve as an animal model to predict human applications.
Isolation and culture of sheep foetal bone marrow cells were done and uniform clonally derived MSC population was collected. The cells were characterized using cytochemical, immunophenotyping, biochemical and molecular analyses. The cells with defined characteristics were differentiated into osteogenic lineages and analysis for differentiated cell types was done. The cells were analyzed for cell surface marker expression and the gene expression in undifferentiated and differentiated osteoblast was checked by reverse transcriptase PCR (RT PCR) analysis and confirmed by sequencing using genetic analyzer.
Ovine foetal samples were processed to obtain mononuclear (MNC) cells which on culture showed spindle morphology, a characteristic oval body with the flattened ends. MSC population CD45-/CD14- was cultured by limiting dilution to arrive at uniform spindle morphology cells and colony forming units. The cells were shown to be positive for surface markers such as CD44, CD54, integrinβ1, and intracellular collagen type I/III and fibronectin. The osteogenically induced MSCs were analyzed for alkaline phosphatase (ALP) activity and mineral deposition. The undifferentiated MSCs expressed RAB3B, candidate marker for stemness in MSCs. The osteogenically induced and uninduced MSCs expressed collagen type I and MMP13 gene in osteogenic induced cells.
Interpretation & conclusions:
The protocol for isolation of ovine foetal bone marrow derived MSCs was simple to perform, and the cultural method of obtaining pure spindle morphology cells was established. Criteria proposed for defining MSCs by this study includes the cell adherence to culture plates, specific surface protein profiles and differentiation to osteogenic lineage. The MSCs and osteogenic differentiated cells in this ovine animal model may serve as a large source for stem cell applications in regenerative medical therapies.
PMCID: PMC3657854  PMID: 23563374
Bone marrow; characterization; differentiation; foetal; MACS; mesenchymal stem cells; multilineage; multipotent; osteogenic
2.  Isolation and multilineage differentiation of bone marrow mesenchymal stem cells from abattoir-derived bovine fetuses 
Mesenchymal stem cells (MSC) are multipotent progenitor cells localized in the stromal compartment of the bone marrow (BM). The potential of MSC for mesenchymal differentiation has been well documented in different animal models predominantly on rodents. However, information regarding bovine MSC (bMSC) is limited, and the differentiation potential of bMSC derived from fetal BM remains unknown. In the present study we sought to isolate bMSC from abattoir-derived fetal BM and to characterize the multipotent and differentiation potential under osteogenic, chondrogenic and adipogenic conditions by quantitative and qualitative analyses.
Plastic-adherent bMSC isolated from fetal BM maintained a fibroblast-like morphology under monolayer culture conditions. These cells expressed high levels of MSC surface markers (CD73, CD90, and CD105) and low levels of hematopoietic surface markers (CD34 and CD45). Culture of bMSC under osteogenic conditions during a 27-day period induced up-regulation of the osteocalcin (OC) gene expression and alkaline phosphatase (ALPL) activity, and promoted mineralization of the matrix. Increasing supplementation levels of ascorbic acid to culture media enhanced osteogenic differentiation of bMSC; whereas, reduction of FBS supplementation compromised osteogenesis. bMSC increased expression of cartilage-specific genes aggrecan (ACAN), collagen 2A1 (COL2A1) and SRY (sex-determining region Y) box 9 (SOX9) at Day 21 of chondrogenic differentiation. Treatment of bMSC with adipogenic factors increased levels of fatty acid-binding protein 2 (AP2) mRNA and accumulation of lipid vacuoles after 18 days of culture. NANOG mRNA levels in differentiating bMSC were not affected during adipogenic culture; however, osteogenic and chondrogenic conditions induced higher and lower levels, respectively.
Our analyses revealed the potential multilineage differentiation of bMSC isolated from abattoir-derived fetal BM. NANOG mRNA pattern in differentiating bMSC varied according to differentiation culture conditions. The osteogenic differentiation of bMSC was affected by ascorbic acid and FBS concentrations in culture media. The simplicity of isolation and the differentiation potential suggest that bMSC from abattoir-derived fetal BM are appropriate candidate for investigating MSC biology and for eventual applications for regenerative therapy.
PMCID: PMC3751243  PMID: 23826829
Mesenchymal stem cell; Bovine fetuses; Differentiation potential; Multipotency
3.  High Throughput Transcriptome Profiling of Lithium Stimulated Human Mesenchymal Stem Cells Reveals Priming towards Osteoblastic Lineage 
PLoS ONE  2013;8(1):e55769.
Human mesenchymal stem cells (hMSCs) present in the bone marrow are the precursors of osteoblasts, chondrocytes and adipocytes, and hold tremendous potential for osteoregenerative therapy. However, achieving directed differentiation into osteoblasts has been a major concern. The use of lithium for enhancing osteogenic differentiation has been documented in animal models but its effect in humans is not clear. We, therefore, performed high throughput transcriptome analysis of lithium-treated hMSCs to identify altered gene expression and its relevance to osteogenic differentiation. Our results show suppression of proliferation and enhancement of alkaline phosphatase (ALP) activity upon lithium treatment of hMSCs under non-osteogenic conditions. Microarray profiling of lithium-stimulated hMSC revealed decreased expression of adipogenic genes (CEBPA, CMKLR1, HSD11B1) and genes involved in lipid biosynthesis. Interestingly, osteoclastogenic factors and immune responsive genes (IL7, IL8, CXCL1, CXCL12, CCL20) were also downregulated. Negative transcriptional regulators of the osteogenic program (TWIST1 and PBX1) were suppressed while genes involved in mineralization like CLEC3B and ATF4 were induced. Gene ontology analysis revealed enrichment of upregulated genes related to mesenchymal cell differentiation and signal transduction. Lithium priming led to enhanced collagen 1 synthesis and osteogenic induction of lithium pretreated MSCs resulted in enhanced expression of Runx2, ALP and bone sialoprotein. However, siRNA-mediated knockdown of RRAD, CLEC3B and ATF4 attenuated lithium-induced osteogenic priming, identifying a role for RRAD, a member of small GTP binding protein family, in osteoblast differentiation. In conclusion, our data highlight the transcriptome reprogramming potential of lithium resulting in higher propensity of lithium “primed” MSCs for osteoblastic differentiation.
PMCID: PMC3559497  PMID: 23383279
4.  Osteogenic Protein-1 for Long Bone Nonunion 
Executive Summary
To assess the efficacy of osteogenic protein-1 (OP-1) for long bone nonunion.
Clinical Need
Although most fractures heal within a normal period, about 5% to 10% do not heal and are classified as delayed or nonunion fractures. Nonunion and segmental bone loss after fracture, reconstructive surgery, or lesion excision can present complex orthopedic problems, and the multiple surgical procedures often needed are associated with patient morbidity and reduced quality of life.
Many factors contribute to the pathogenesis of a delayed union or nonunion fractures, including deficiencies of calcium, vitamin D, or vitamin C, and side effects of medications such as anticoagulants, steroids, some anti-inflammatory drugs, and radiation. It has been shown that smoking interferes with bone repair in several ways.
Incidence of Nonunion and Delayed Union Cases
An estimated 5% to 10% of fractures do not heal properly and go on to delayed union or nonunion. If this overall estimate of incidence were applied to the Ontario population1, the estimated number of delayed union or nonunion in the province would be between 3,863 and 7,725.
Treatment of Nonunion Cases
The treatment of nonunion cases is a challenge to orthopedic surgeons. However, the basic principle behind treatment is to provide both mechanical and biological support to the nonunion site.
Fracture stabilization and immobilization is frequently used with the other treatment modalities that provide biological support to the fractured bone. Biological support includes materials that could be served as a source of osteogenic cells (osteogenesis), a stimulator of mesenchymal cells (osteoinduction), or a scaffold-like structure (osteoconduction).
The capacity to heal a fracture is a latent potential of the stromal stem cells, which synthesize new bone. This process has been defined as osteogenesis. Activation of the stem cells to initiate osteogenic response and to differentiate into bone-forming osteoblasts is called osteoinduction. These 2 properties accelerate the rate of fracture healing or reactivate the ineffective healing process. Osteoconduction occurs when passive structures facilitate the migration of osteoprogenitor cells, the perivascular tissue, and capillaries into these structures.
Bone Grafts and Bone Graft Substitutes
Bone graft and bone graft substitutes have one or more of the following components:
Undifferentiated stem cells
Growth factors
Structural lattice
Undifferentiated stem cells are unspecialized, multipotential cells that can differentiate into a variety of specialized cells. They can also replicate themselves. The role of stem cells is to maintain and repair the tissue in which they are residing. A single stem cell can generate all cell types of that tissue. Bone marrow is a source of at least 2 kinds of stem cells. Hematopoietic stem cells that form all types of blood cells, and bone marrow stromal stem cells that have osteogenic properties and can generate bone, cartilage, and fibrous tissue.
Bone marrow has been used to stimulate bone formation in bone defects and cases of nonunion fractures. Bone marrow can be aspirated from the iliac crest and injected percutaneously with fluoroscopic guidance into the site of the nonunion fracture. The effectiveness of this technique depends on the number and activity of stem cells in the aspirated bone marrow. It may be possible to increase the proliferation and speed differentiation of stem cells by exposing them to growth factor or by combining them with collagen.
Many growth factors and cytokines induced in response to injury are believed to have a considerable role in the process of repair. Of the many bone growth factors studied, bone morphogenetics (BMPs) have generated the greatest attention because of their osteoinductive potential. The BMPs that have been most widely studied for their ability to induce bone regeneration in humans include BMP-2 and BMP-7 (osteogenic protein). Human osteogenic protein-1 (OP-1) has been cloned and produced with recombinant technology and is free from the risk of infection or allergic reaction.
The structural lattice is osteoconductive; it supports the ingrowth of developing capillaries and perivascular tissues. Three distinct groups of structural lattice have been identified: collagen, calcium sulphate, and calcium phosphate. These materials can be used to replace a lost segment of bone.
Grafts Used for Nonunion
Autologous bone graft is generally considered the gold standard and the best material for grafting because it contains several elements that are critical in promoting bone formation, including osteoprogenitor cells, the matrix, and bone morphogenetic proteins. The osteoconductive property of cancellous autograft is related to the porosity of bone. The highly porous, scaffold-like structure of the graft allows host osteoblasts and host osteoprogenitor cells to migrate easily into the area of the defect and to begin regeneration of bone. Sources of cancellous bone are the iliac crest, the distal femur, the greater trochanter, and the proximal tibia. However, harvesting the autologous bone graft is associated with postoperative pain at the donor site, potential injury to the surrounding arteries, nerves, and tissues, and the risk of infection. Thus the development of synthetic materials with osteoconductive and osteoinductive properties that can eliminate the need for harvesting has become a major goal of orthopedic research.
Allograft is the graft of tissue between individuals who are of the same species but are of a disparate genotype. Allograft has osteoconductive and limited osteoinductive properties. Demineralized bone matrix (DBM) is human cortical and cancellous allograft. These products are prepared by acid extraction of allograft bone, resulting in the loss of most of the mineralized component while collagen and noncollagenous proteins, including growth factors, are retained. Figures 1 to 5 demonstrate the osteogenic, osteoinduction, and osteoconduction properties of autologous bone graft, allograft, OP-1, bone graft substitutes, and bone marrow.
Autologous Bone Graft
Osteogenic Protein-1
Allograft bone and Demineralized Bone Matrix
Bone Graft Substitutes
Autologous Bone Marrow Graft
New Technology Being Reviewed: Osteogenic Protein-1
Health Canada issued a Class IV licence for OP-1 in June 2004 (licence number 36320). The manufacturer of OP-1 is Stryker Biotech (Hapkinton, MA).
The United States Food and Drug Administration (FDA) issued a humanitarian device exemption for the application of the OP-1 implant as an “alternative to autograft in recalcitrant long bone nonunions where use of autograft is unfeasible and alternative treatments have failed.” Regulatory agencies in Europe, Australia, and New Zealand have permitted the use of this implant in specific cases, such as in tibial nonunions, or in more general cases, such as in long bone nonunions.
According to the manufacturer, OP-1 is indicated for the treatment of long bone nonunions. It is contraindicated in the patient has a hypersensitivity to the active substance or collagen, and it should not be applied at the site of a resected tumour that is at or near the defect or fracture. Finally, it should not be used in patients who are skeletally immature (< 18 years of age), or if there is no radiological evidence of closure of epiphysis.
Review Strategy
To summarize the safety profile and effectiveness of OP-1 in the treatment of cases of long bone nonunion and bone defects
To compare the effectiveness and cost effectiveness of OP-1 in the treatment of long bone nonunions and bone defects with the alternative technologies, particularly the gold standard autologous bone graft.
Literature Search
International Network of Agencies for Health Technology Assessments (INAHTA), the Cochrane Database of Systematic Reviews and the CCTR (formerly Cochrane Controlled Trials Register) were searched for health technology assessments. MEDLINE, EMBASE, Medline In Process and Other Non-Indexed Citations were searched from January 1, 1996 to January 27, 2004 for studies on OP-1. The search was limited to English-language articles and human studies. The search yielded 47 citations. Three studies met inclusion criteria (2 RCTs and 1 Ontario-based study presented at an international conference.
Summary of Findings
Friedlaender et al. conducted a prospective, randomized, partially blinded clinical trial on the treatment tibial nonunions with OP-1. Tibial nonunions were chosen for this study because of their high frequency, challenging treatment requirements, and substantial morbidity. All of the nonunions were at least 9 months old and had shown no progress toward healing over the previous 3 months. The patients were randomized to receive either treatment with autologous bone grafting or treatment with OP-1 in a type-1 collagen carrier. Both groups received reduction and fixation with an intramedullary rod. Table 1 summarizes the clinical outcomes of this study.
Outcomes in a Randomized Clinical Trial on Tibial Nonunions: Osteogenic Protein-1 versus Autologous Bone Grafting
Clinical success was defined as full weight-bearing, loss of severe pain at the fracture site on weight-bearing, and no further surgical treatment to enhance fracture repair.
The results of this study demonstrated that recombinant OP-1 is associated with substantial clinical and radiographic success for the treatment of tibial nonunions when used with intramedullary rod fixation. No adverse event related to sensitization was reported. Five per cent of the patients in the OP-1 group had circulating antibodies against type 1 collagen. Only 10% of the patients had a low level of anti-OP-1 antibodies, and all effects were transient. Furthermore, the success rate with the OP-1 implant was comparable with those achieved with autograft at 9 and 24 months follow-up. Eighty-two per cent of patients were successful at 24 months follow-up in both groups.
Statistically significant increased blood loss in the group treated with the autograft was observed (P = .049). Patients treated with autograft had longer operation and hospitalization times. All patients in the autograft group had pain at the donor site after surgery, and more than 80% judged their postoperative pain as moderate or severe. At their 6-month visit, 20% of the patients in the autograft group had persistent pain, mild or moderate in nature, at the donor site. This number fell to 13% at 12 months.
All patients in each of the groups had at least 1 adverse event that wasn’t serious, such as fever, nausea and vomiting, leg edema, discomfort, and bruising at the operative site. The incidence of these events was similar in both groups. Serious adverse events were observed in 44% of both groups, none of which were considered related to the OP-1 implant or autograft.
On the basis of this data, the FDA issued a humanitarian device exemption for the application of OP-1 implant as an alternative to autograft in recalcitrant long bone nonunions when the use of autograft is unfeasible and alternative treatments have failed.
Study on Fibular Defects
Geesink et al. investigated the osteogenic activity of OP-1 by assessing its value in bridging fibular defects made at the time of tibial osteotomy for varus or valgus deformity of the knee. This study had 2 phases and included 12 patients in each phase. Each phase included 12 patients (6 in each group). Patients in the first phase received either DBM or were left untreated. Patients in the second phase received either OP-1 on collagen type-1 or collagen type-1 alone.
Radiological and Dual Energy X-ray Absorptiometry (DEXA) evaluation showed that in patients in whom the defect was left untreated, no formation of bone occurred. At 12 months follow-up, new bone formation with bridging occurred in 4 of the 6 patients in DMB group, and 5 of the 6 patients in OP-1 group. One patient in OP-1 group did not show any evidence of new bone formation at any point during the study.
Ontario Pilot Study
A prospective pilot study was conducted in Ontario, Canada to investigate the safety and efficacy of OP-1 for the treatment of recalcitrant long bone nonunions. The study looked at 15 patients with complex, recalcitrant, long bone nonunions whose previous treatment had failed. The investigators concluded that this bone graft substitute appears to be safe and effective in providing sufficient biological stimulation in difficult to treat nonunions. Results of a more complete study on 70 patients are ready for publication. According to the principal investigator, OP-1 was 90% effective in inducing bone formation and bone healing in this sample.
Alternative Technologies
The Medical Advisory Secretariat conducted a literature search from January 1, 2000 to February 28, 2005 to identify studies on nonunions/bone defects that had been treated with alternative technologies. A review of these studies showed that, in addition to the gold standard autologous bone marrow grafting, bone allografts, demineralized bone matrices, bone graft substitutes, and autologous bone marrow have been used for treatment of nonunions and bone defects. These studies were categorized according to the osteoinductive, osteoconductive, and osteogenesis properties of the technologies studied.
A review of these studies showed that bone allografts have been used mostly in various reconstruction procedures to restore the defect after excavating a bone lesion. Two studies investigated the effectiveness of DBM in healing fracture nonunions. Calcium phosphate and calcium sulphate have been used mostly for repair of bone defects.
Several investigators have looked at the use of autologous bone marrow for treatment of long bone nonunions. The results of these studies show that method of percutaneous bone marrow grafting is highly effective in the treatment of long bone nonunions. In a total of 301 fractures across all studies, 268 (89%) healed with a mean healing time of 2.5 to 8 months. This healing time as derived from these case series is less than the timing of the primary end point in Friedlaender’s study (9 months). Table 2 summarizes the results of these studies. Table 2 summarizes the results of these studies.
Studies that used Percutaneous Bone Marrow Grafting for Treatment of Nonunions
Economic Analysis
Based on annual estimated incidence of long-bone nonunion of 3,863 - 7,725, the annual hospitalization costs associated with this condition is between $21.2 and $42.3 million based on a unit cost of $5,477 per hospital separation. When utilized, the device, a single vial of OP-1, is approximately $5,000 and if adopted universally in Ontario, the total device costs would be in the range of $19.3 - $38.6 million annually. The physician fee for harvest, insertion of bone, or OP-1 is $193 and is $193 for autologous bone marrow transplantation. Total annual physician costs are expected to be in the range of from $0.7 million to $1.3 million per year. Expenditures associated with long-bone nonunion are unlikely to increase since incidence of long-bone nonunion is unlikely to change in the future. However, the rate of uptake of OP-1 could have a significant impact on costs if the uptake were large.
The use of OP-1 and autologous bone marrow transplantation may offset pain medication costs compared with those associated with autologous bone harvest given that the former procedures do not involve the pain associated with the bone harvest site. However, given that this pain is normally not permanent, the overall offset is likely to be small. There are likely to be smaller OHIP costs associated with OP-1 than bone-harvest procedures given that only 1, rather than 2, incisions are needed when comparing the former with the latter procedure. This offset could amount to between $0.3 million to $0.7 million annually.
No data on the cost-effectiveness of OP-1 is available.
PMCID: PMC3382627  PMID: 23074475
5.  Use of RUNX2 Expression to Identify Osteogenic Progenitor Cells Derived from Human Embryonic Stem Cells 
Stem Cell Reports  2015;4(2):190-198.
We generated a RUNX2-yellow fluorescent protein (YFP) reporter system to study osteogenic development from human embryonic stem cells (hESCs). Our studies demonstrate the fidelity of YFP expression with expression of RUNX2 and other osteogenic genes in hESC-derived osteoprogenitor cells, as well as the osteogenic specificity of YFP signal. In vitro studies confirm that the hESC-derived YFP+ cells have similar osteogenic phenotypes to osteoprogenitor cells generated from bone-marrow mesenchymal stem cells. In vivo studies demonstrate the hESC-derived YFP+ cells can repair a calvarial defect in immunodeficient mice. Using the engineered hESCs, we monitored the osteogenic development and explored the roles of osteogenic supplements BMP2 and FGF9 in osteogenic differentiation of these hESCs in vitro. Taken together, this reporter system provides a novel system to monitor the osteogenic differentiation of hESCs and becomes useful to identify soluble agents and cell signaling pathways that mediate early stages of human bone development.
•This reporter system represents RUNX2 expression in osteogenic differentiated hESCs•This system can be used to identify stages of osteogenic development of hESCs•BMP2 alone does not induce osteogenic differentiation of hESCs in vitro
In these studies, Kaufman and colleagues show that the reporter system they generated faithfully represents the expression of RUNX2 gene during osteogenic development using hESCs. Using this system, they evaluate the osteogenic differentiation of hESCs at early stage and investigate the osteogenic effect of BMP2 on hESCs in vitro. The selected hESC-derived osteogenic cells also mediate bone repair in vivo.
PMCID: PMC4325195
6.  Proteomics reveals multiple routes to the osteogenic phenotype in mesenchymal stem cells 
BMC Genomics  2007;8:380.
Recently, we demonstrated that human mesenchymal stem cells (hMSC) stimulated with dexamethazone undergo gene focusing during osteogenic differentiation (Stem Cells Dev 14(6): 1608–20, 2005). Here, we examine the protein expression profiles of three additional populations of hMSC stimulated to undergo osteogenic differentiation via either contact with pro-osteogenic extracellular matrix (ECM) proteins (collagen I, vitronectin, or laminin-5) or osteogenic media supplements (OS media). Specifically, we annotate these four protein expression profiles, as well as profiles from naïve hMSC and differentiated human osteoblasts (hOST), with known gene ontologies and analyze them as a tensor with modes for the expressed proteins, gene ontologies, and stimulants.
Direct component analysis in the gene ontology space identifies three components that account for 90% of the variance between hMSC, osteoblasts, and the four stimulated hMSC populations. The directed component maps the differentiation stages of the stimulated stem cell populations along the differentiation axis created by the difference in the expression profiles of hMSC and hOST. Surprisingly, hMSC treated with ECM proteins lie closer to osteoblasts than do hMSC treated with OS media. Additionally, the second component demonstrates that proteomic profiles of collagen I- and vitronectin-stimulated hMSC are distinct from those of OS-stimulated cells. A three-mode tensor analysis reveals additional focus proteins critical for characterizing the phenotypic variations between naïve hMSC, partially differentiated hMSC, and hOST.
The differences between the proteomic profiles of OS-stimulated hMSC and ECM-hMSC characterize different transitional phenotypes en route to becoming osteoblasts. This conclusion is arrived at via a three-mode tensor analysis validated using hMSC plated on laminin-5.
PMCID: PMC2148065  PMID: 17949499
7.  Inhibition of ERK Promotes Collagen Gel Compaction and Fibrillogenesis to Amplify the Osteogenesis of Human Mesenchymal Stem Cells in Three-Dimensional Collagen I Culture 
Stem Cells and Development  2009;18(2):331-341.
Tissue morphogenesis remains one of the least understood problems in cell and developmental biology. There is a disconnect between the mechanisms that apply to two-dimensional (2D) cultures and those seen in vivo. Three-dimensional (3D) culture presents a complex stimulus triggering cellular responses that are only partially understood. We compared 2D and 3D cultures of human mesenchymal stem cells in the presence of mitogen-activated protein kinase kinase (MEK) inhibitor, PD98059, to determine the role of extracellular signal-related kinase (ERK) in collagen-induced differentiation. 3D collagen I culture enhanced and accelerated the osteogenic differentiation of human mesenchymal stem cells (hMSC). Contrary to 2D results, the addition of PD98059 induced a significant amplification of osteogenic gene expression and matrix mineralization in 3D cultures. The inhibition of ERK altered cell-mediated compaction, proliferation, and resulted in the development of distinct tissue microstructure. Therefore, we suggest that the ability to reorganize collagen in 3D is an important step in ERK-mediated osteogenic differentiation. This work aims to propose a correlation between osteogenic differentiation and hMSC-directed collagen I remodeling. We present a potential mechanistic link (ERK) through which the three dimensionality of an engineered tissue acts to differentially induce and maintain cellular phenotype during tissue development.
PMCID: PMC2656582  PMID: 18491946
8.  Microarray Analysis of Human Adipose-Derived Stem Cells in Three-Dimensional Collagen Culture: Osteogenesis Inhibits Bone Morphogenic Protein and Wnt Signaling Pathways, and Cyclic Tensile Strain Causes Upregulation of Proinflammatory Cytokine Regulators and Angiogenic Factors 
Tissue Engineering. Part A  2011;17(21-22):2615-2627.
Human adipose-derived stem cells (hASC) have shown great potential for bone tissue engineering. However, the molecular mechanisms underlying this potential are not yet known, in particular the separate and combined effects of three-dimensional (3D) culture and mechanical loading on hASC osteogenesis. Mechanical stimuli play a pivotal role in bone formation, remodeling, and fracture repair. To further understand hASC osteogenic differentiation and response to mechanical stimuli, gene expression profiles of proliferating or osteogenically induced hASC in 3D collagen I culture in the presence and absence of 10% uniaxial cyclic tensile strain were examined using microarray analysis. About 847 genes and 95 canonical pathways were affected during osteogenesis of hASC in 3D culture. Pathway analysis indicated the potential roles of Wnt/β-catenin signaling, bone morphogenic protein (BMP) signaling, platelet-derived growth factor (PDGF) signaling, and insulin-like growth factor 1 (IGF-1) signaling in hASC during osteogenic differentiation. Application of 10% uniaxial cyclic tensile strain suggested synergistic effects of strain with osteogenic differentiation media on hASC osteogenesis as indicated by significantly increased calcium accretion of hASC. There was no significant further alteration in the four major pathways (Wnt/β-catenin, BMP, PDGF, and IGF-1). However, 184 transcripts were affected by 10% cyclic tensile strain. Function and network analysis of these transcripts suggested that 10% cyclic tensile strain may play a role during hASC osteogenic differentiation by upregulating two crucial factors in bone regeneration: (1) proinflammatory cytokine regulators interleukin 1 receptor antagonist and suppressor of cytokine signaling 3; (2) known angiogenic inductors fibroblast growth factor 2, matrix metalloproteinase 2, and vascular endothelial growth factor A. This is the first study to investigate the effects of both 3D culture and mechanical load on hASC osteogenic differentiation. A complete microarray analysis investigating both the separate effect of soluble osteogenic inductive factors and the combined effects of chemical and mechanical stimulation was performed on hASC undergoing osteogenic differentiation. We have identified specific genes and pathways associated with mechanical response and osteogenic potential of hASC, thus providing significant information toward improved understanding of our use of hASC for functional bone tissue engineering applications.
PMCID: PMC3204199  PMID: 21767168
9.  The Marine Sponge-Derived Inorganic Polymers, Biosilica and Polyphosphate, as Morphogenetically Active Matrices/Scaffolds for the Differentiation of Human Multipotent Stromal Cells: Potential Application in 3D Printing and Distraction Osteogenesis 
Marine Drugs  2014;12(2):1131-1147.
The two marine inorganic polymers, biosilica (BS), enzymatically synthesized from ortho-silicate, and polyphosphate (polyP), a likewise enzymatically synthesized polymer consisting of 10 to >100 phosphate residues linked by high-energy phosphoanhydride bonds, have previously been shown to display a morphogenetic effect on osteoblasts. In the present study, the effect of these polymers on the differential differentiation of human multipotent stromal cells (hMSC), mesenchymal stem cells, that had been encapsulated into beads of the biocompatible plant polymer alginate, was studied. The differentiation of the hMSCs in the alginate beads was directed either to the osteogenic cell lineage by exposure to an osteogenic medium (mineralization activation cocktail; differentiation into osteoblasts) or to the chondrogenic cell lineage by incubating in chondrocyte differentiation medium (triggering chondrocyte maturation). Both biosilica and polyP, applied as Ca2+ salts, were found to induce an increased mineralization in osteogenic cells; these inorganic polymers display also morphogenetic potential. The effects were substantiated by gene expression studies, which revealed that biosilica and polyP strongly and significantly increase the expression of bone morphogenetic protein 2 (BMP-2) and alkaline phosphatase (ALP) in osteogenic cells, which was significantly more pronounced in osteogenic versus chondrogenic cells. A differential effect of the two polymers was seen on the expression of the two collagen types, I and II. While collagen Type I is highly expressed in osteogenic cells, but not in chondrogenic cells after exposure to biosilica or polyP, the upregulation of the steady-state level of collagen Type II transcripts in chondrogenic cells is comparably stronger than in osteogenic cells. It is concluded that the two polymers, biosilica and polyP, are morphogenetically active additives for the otherwise biologically inert alginate polymer. It is proposed that alginate, supplemented with polyP and/or biosilica, is a suitable biomaterial that promotes the growth and differentiation of hMSCs and might be beneficial for application in 3D tissue printing of hMSCs and for the delivery of hMSCs in fractures, surgically created during distraction osteogenesis.
PMCID: PMC3944534  PMID: 24566262
biosilica; polyphosphate; multipotent stromal cells; mesenchymal stem cells; alkaline phosphatase; 3D cell/tissue printing; distraction osteogenesis
10.  Chordin knockdown enhances the osteogenic differentiation of human mesenchymal stem cells 
Bone morphogenetic proteins (BMPs) are critical growth factors in the osteogenic differentiation of progenitor cells during development in embryos and fracture repair in adults. Although recombinant BMPs are in use clinically, their clinical efficiency needs to be improved. The biological activities of BMPs are naturally regulated by extracellular binding proteins. The specific hypotheses tested in this study were as follows: the BMP inhibitor chordin is produced endogenously during the osteogenic differentiation of human mesenchymal stem cells (MSCs); and blockade of the activity of the BMP inhibitor increases the rate of osteogenic differentiation of human MSCs in vitro.
Human MSCs were derived from bone marrow from an iliac crest aspirate and from patients undergoing hip hemiarthroplasty. The MSCs were induced down the osteogenic pathway using standard osteogenic differentiation media, and expressions of BMP-2 and chordin were determined by gene expression analysis. During osteogenic differentiation, chordin knockdown was induced using RNA interference. Osteogenic differentiation was assessed by measuring the expression of alkaline phosphatase and calcium deposition. The differences in expression of osteogenic makers between groups were compared by analysis of variance, followed by Gabriel post hoc test.
We demonstrate the expression of BMP-2 and chordin in human MSCs during osteogenic differentiation. Knockdown of chordin by RNA interference in vitro resulted in a significant increase in the expression of the osteogenic marker alkaline phosphatase and the deposition of extracellular mineral, in response to osteogenic stimulation.
We conclude that endogenously produced chordin constrains the osteogenic differentiation of human MSCs. The targeting of BMP inhibitors, such as chordin, may provide a novel strategy for enhancing bone regeneration.
PMCID: PMC2483456  PMID: 18533030
11.  Laminin-5 activates extracellular matrix production and osteogenic gene focusing in human mesenchymal stem cells 
We recently reported that laminin-5, expressed by human mesenchymal stem cells (hMSC), stimulates osteogenic gene expression in these cells in the absence of any other osteogenic stimulus. Here we employ two dimensional liquid chromatography and tandem mass spectrometry, along with the Database for Annotation, Visualization and Integrated Discovery (DAVID), to obtain a more comprehensive profile of the protein (and hence gene) expression changes occurring during laminin-5-induced osteogenesis of hMSC. Specifically, we compare the protein expression profiles of undifferentiated hMSC, hMSC cultured on laminin-5 (Ln-5 hMSC), and fully differentiated human osteoblasts (hOST) with profiles from hMSC treated with well-established osteogenic stimuli (collagen I, vitronectin, or dexamethazone). We find a marked reduction in the number of proteins (e.g., those involved with calcium signaling and cellular metabolism) expressed in Ln-5 hMSC compared to hMSC, consistent with our previous finding that hOST express far fewer proteins than do their hMSC progenitors, a pattern we call “osteogenic gene focusing.” This focused set, which resembles an intermediate stage between hMSC and mature hOST, mirrors the expression profiles of hMSC exposed to established osteogenic stimuli and includes osteogenic extracellular matrix proteins (collagen, vitronectin) and their integrin receptors, calcium signaling proteins, and enzymes involved in lipid metabolism. These results provide direct evidence that laminin-5 alone stimulates global changes in gene/protein expression in hMSC that lead to commitment of these cells to the osteogenic phenotype, and that this commitment correlates with extracellular matrix production.
PMCID: PMC1852504  PMID: 17137774
Laminin-5; extracellular matrix; mesenchymal stem cells; osteogenesis
12.  Hesperetin Alleviates the Inhibitory Effects of High Glucose on the Osteoblastic Differentiation of Periodontal Ligament Stem Cells 
PLoS ONE  2013;8(6):e67504.
Hesperetin (3′,5,7-trihydroxy-4-methoxyflavanone) is a metabolite of hesperidin (hesperetin-7-O-rutinoside), which belongs to the flavanone subgroup and is found mainly in citrus fruits. Hesperetin has been reported to be an effective osteoinductive compound in various in vivo and in vitro models. However, how hesperetin effects osteogenic differentiation is not fully understood. In this study, we investigated the capacity of hesperetin to stimulate the osteogenic differentiation of periodontal ligament stem cells (PDLSCs) and to relieve the anti-osteogenic effect of high glucose. Osteogenesis of PDLSCs was assessed by measurement of alkaline phosphatase (ALP) activity, and evaluation of the mRNA expression of ALP, runt-related gene 2 (Runx2), osterix (OSX), and FRA1 as osteogenic transcription factors, as well as assessment of protein expression of osteopontin (OPN) and collagen type IA (COLIA). When PDLSCs were exposed to a high concentration (30 mM) of glucose, osteogenic activity decreased compared to control cells. Hesperetin significantly increased ALP activity at doses of 1, 10, and 100 µM. Pretreatment of cells with hesperetin alleviated the high-glucose-induced suppression of the osteogenic activity of PDLSCs. Hesperetin scavenged intracellular reactive oxygen species (ROS) produced under high glucose condition. Furthermore, hesperetin increased the activity of the PI3K/Akt and β-catenin pathways. Consistent with this, blockage of Akt or β-catenin diminished the protective effect of hesperetin against high glucose-inhibited osteogenic differentiation. Collectively, our results suggest that hesperetin alleviates the high glucose-mediated suppression of osteogenic differentiation in PDLSCs by regulating ROS levels and the PI3K/Akt and β-catenin signaling pathways.
PMCID: PMC3696082  PMID: 23840726
13.  Effects of different serum conditions on osteogenic differentiation of human adipose stem cells in vitro 
Currently, human adipose stem cells (hASCs) are differentiated towards osteogenic lineages using culture medium supplemented with L-ascorbic acid 2-phosphate (AsA2-P), dexamethasone (Dex) and beta-glycerophosphate (β-GP). Because this osteogenic medium (OM1) was initially generated for the differentiation of bone marrow-derived mesenchymal stem cells, the component concentrations may not be optimal for the differentiation of hASCs. After preliminary screening, two efficient osteogenic media (OM2 and OM3) were chosen to be compared with the commonly used osteogenic medium (OM1). To further develop the culture conditions towards clinical usage, the osteo-inductive efficiencies of OM1, OM2 and OM3 were compared using human serum (HS)-based medium and a defined, xeno-free medium (RegES), with fetal bovine serum (FBS)-based medium serving as a control.
To compare the osteo-inductive efficiency of OM1, OM2 and OM3 in FBS-, HS- and RegES-based medium, the osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity, mineralization, and expression of osteogenic marker genes (runx2A, DLX5, collagen type I, osteocalcin, and ALP).
In HS-based medium, the ALP activity increased significantly by OM3, and mineralization was enhanced by both OM2 and OM3, which have high AsA2-P and low Dex concentrations. ALP activity and mineralization of hASCs was the weakest in FBS-based medium, with no significant differences between the OM compositions due to donor variation. However, the qRT-PCR data demonstrated significant upregulation of runx2A mRNA under osteogenic differentiation in FBS- and HS-based medium, particularly by OM3 under FBS conditions. Further, the expression of DLX5 was greatly stimulated by OM1 to 3 on day 7 when compared to control. The regulation of collagen type I, ALP, and osteocalcin mRNA was modest under induction by OM1 to 3. The RegES medium was found to support the proliferation and osteogenic differentiation of hASCs, but the composition of the RegES medium hindered the comparison of OM1, OM2 and OM3.
Serum conditions affect hASC proliferation and differentiation significantly. The ALP activity and mineralization was the weakest in FBS-based medium, although osteogenic markers were upregulated on mRNA level. When comparing the OM composition, the commonly used OM1 was least effective. Accordingly, higher concentration of AsA2-P and lower concentration of Dex, as in OM2 and OM3, should be used for the osteogenic differentiation of hASCs in vitro.
PMCID: PMC3706769  PMID: 23415114
14.  Three-dimensional multipotent progenitor cell aggregates for expansion, osteogenic differentiation and “in vivo” tracing with AAV vector serotype 6 
Gene therapy  2012;20(2):158-168.
Multipotent adult progenitor cells (MAPC) are bone marrow-derived stem cells with a high growth rate suitable for therapeutical applications as three-dimensional (3D) aggregates. Combined applications of osteogenically differentiated MAPC (OD-MAPC) aggregates and adeno-associated viral vectors (AAV) in bone bioengineering are still deferred until information regarding expansion technologies, osteogenic potential, and AAV cytotoxicity and transduction efficiency is better understood. In this study, we tested whether self-complementary AAV (scAAV) can potentially be used as a gene delivery system in a OD-MAPC-based “in vivo” bone formation model in the craniofacial region. Both expansion of rat MAPC (rMAPC) and osteogenic differentiation with dexamethasone were also tested in 3D aggregate culture systems “in vitro” and “vivo”. Rat MAPCs (rMAPCs) grew as undifferentiated aggregates for 4 days with a population doubling time of 37h. After expansion, constant levels of Oct4 transcripts, and Oct4 and CD31 surface markers were observed, which constitute a hallmark of rMAPCs undifferentiated stage. Dexamethasone effectively mediated rMAPC osteogenic differentiation by inducing the formation of a mineralized collagen type I network, and facilitated the activation of the wnt/β-catenin, a crucial pathway in skeletal development. To investigate the genetic modification of rMAPCs grown as 3D aggregates prior to implantation, scAAV serotypes 2, 3, and 6 were evaluated. scAAV6 packaged with the enhanced green fluorescent protein expression cassette efficiently mediated long-term transduction (10 days) “in vitro” and “vivo”. The reporter transduction event allowed the tracing of OD-rMAPC (induced by dexamethasone) aggregates following OD-rMAPC transfer into a macro-porous hydroxyapatite scaffold implanted in a rat calvaria model. Furthermore, the scAAV6-transduced OD-rMAPC generated a bone-like matrix with a collagenous matrix rich in bone specific proteins (osteocalcin and osteopontin) in the scaffold macro-pores 10 days post-implantation. Newly formed bone was also observed in the interface between native bone and scaffold. The collective work supports future bone tissue engineering applications of 3D MAPC cultures for expansion, bone formation, and the ability to genetically alter these cells using scAAV vectors.
PMCID: PMC3374053  PMID: 22402320
15.  Phenotypic Characterization, Osteoblastic Differentiation and Bone Regeneration Capacity of Human Embryonic Stem Cell-derived Mesenchymal Stem Cells 
Stem cells and development  2009;18(7):955-968.
To enhance the understanding of differentiation patterns and bone formation capacity of hESCs, we determined (1) the temporal pattern of osteoblastic differentiation of human embryonic stem cell-derived mesenchymal stem cells (hESCs-MSCs), (2) the influence of a three-dimensional matrix on the osteogenic differentiation of hESCs-MSCs in long term culture and (3) the bone forming capacity of osteoblast-like cells derived from hESCs-MSCs in calvarial defects. Incubation of hESCs-MSCs in osteogenic medium induced osteoblastic differentiation of hESCs-MSCs into mature osteoblasts in a similar chronological pattern to human bone marrow stromal cells and primary osteoblasts. Osteogenic differentiation was enhanced by culturing the cells on three-dimensional collagen scaffolds. Fluorescent activated cell sorting of alkaline phosphatase expressing cells was used to obtain an enriched osteogenic cell population for in vivo transplantation. The identification of green fluorescence protein and expression of human specific nuclear antigen in osteocytes in newly formed bone verified the role of transplanted human cells in the bone regeneration process. The current cell culture model and osteogenic cell enrichment method could provide large numbers of osteoprogenitor cells for analysis of differentiation patterns and cell transplantation to regenerate skeletal defects.
PMCID: PMC3032563  PMID: 19327009
16.  Phenotypic Characterization, Osteoblastic Differentiation, and Bone Regeneration Capacity of Human Embryonic Stem Cell–Derived Mesenchymal Stem Cells 
Stem Cells and Development  2009;18(7):955-968.
To enhance the understanding of differentiation patterns and bone formation capacity of hESCs, we determined (1) the temporal pattern of osteoblastic differentiation of human embryonic stem cell–derived mesenchymal stem cells (hESC-MSCs), (2) the influence of a three-dimensional matrix on the osteogenic differentiation of hESC-MSCs in long-term culture, and (3) the bone-forming capacity of osteoblast-like cells derived from hESC-MSCs in calvarial defects. Incubation of hESC-MSCs in osteogenic medium induced osteoblastic differentiation of hESC-MSCs into mature osteoblasts in a similar chronological pattern to human bone marrow stromal cells and primary osteoblasts. Osteogenic differentiation was enhanced by culturing the cells on three-dimensional collagen scaffolds. Fluorescent-activated cell sorting of alkaline phosphatase expressing cells was used to obtain an enriched osteogenic cell population for in vivo transplantation. The identification of green fluorescence protein and expression of human-specific nuclear antigen in osteocytes in newly formed bone verified the role of transplanted human cells in the bone regeneration process. The current cell culture model and osteogenic cell enrichment method could provide large numbers of osteoprogenitor cells for analysis of differentiation patterns and cell transplantation to regenerate skeletal defects.
PMCID: PMC3032563  PMID: 19327009
17.  Stimulation of osteogenic differentiation in human osteoprogenitor cells by pulsed electromagnetic fields: an in vitro study 
Although pulsed electromagnetic field (PEMF) stimulation may be clinically beneficial during fracture healing and for a wide range of bone disorders, there is still debate on its working mechanism. Mesenchymal stem cells are likely mediators facilitating the observed clinical effects of PEMF. Here, we performed in vitro experiments to investigate the effect of PEMF stimulation on human bone marrow-derived stromal cell (BMSC) metabolism and, specifically, whether PEMF can stimulate their osteogenic differentiation.
BMSCs derived from four different donors were cultured in osteogenic medium, with the PEMF treated group being continuously exposed to a 15 Hz, 1 Gauss EM field, consisting of 5-millisecond bursts with 5-microsecond pulses. On culture day 1, 5, 9, and 14, cells were collected for biochemical analysis (DNA amount, alkaline phosphatase activity, calcium deposition), expression of various osteoblast-relevant genes and activation of extracellular signal-regulated kinase (ERK) signaling. Differences between treated and control groups were analyzed using the Wilcoxon signed rank test, and considered significant when p < 0.05.
Biochemical analysis revealed significant, differentiation stage-dependent, PEMF-induced differences: PEMF increased mineralization at day 9 and 14, without altering alkaline phosphatase activity. Cell proliferation, as measured by DNA amounts, was not affected by PEMF until day 14. Here, DNA content stagnated in PEMF treated group, resulting in less DNA compared to control.
Quantitative RT-PCR revealed that during early culture, up to day 9, PEMF treatment increased mRNA levels of bone morphogenetic protein 2, transforming growth factor-beta 1, osteoprotegerin, matrix metalloproteinase-1 and -3, osteocalcin, and bone sialoprotein. In contrast, receptor activator of NF-κB ligand expression was primarily stimulated on day 14. ERK1/2 phosphorylation was not affected by PEMF stimulation.
PEMF exposure of differentiating human BMSCs enhanced mineralization and seemed to induce differentiation at the expense of proliferation. The osteogenic stimulus of PEMF was confirmed by the up-regulation of several osteogenic marker genes in the PEMF treated group, which preceded the deposition of mineral itself. These findings indicate that PEMF can directly stimulate osteoprogenitor cells towards osteogenic differentiation. This supports the theory that PEMF treatment may recruit these cells to facilitate an osteogenic response in vivo.
PMCID: PMC2936347  PMID: 20731873
18.  Osteogenic differentiation is synergistically influenced by osteoinductive treatment and direct cell–cell contact between murine osteoblasts and mesenchymal stem cells 
International Orthopaedics  2011;36(1):199-205.
The present study was designed to address whether osteoblasts play a synergistic role in promoting mesenchymal stem cell (MSC) osteogenesis in a direct cell–cell contact co-culture model.
Murine C3H10T1/2 and MC3T3-E1 cell lines were mixed and plated onto 12-well culture plates and co-cultured at various ratios of initial cell densities. To compare the possible improvement on osteogenic differentiation, co-culture cells were served with or without osteogenic supplements in culture medium.
Weak osteogenesis was induced in MSCs co-cultured in an untreated medium with different ratios of osteoblasts. An osteoblast-dependent increase in osteogenic gene expression of Runx2, type I collagen, and osteocalcin was observed over time. Moreover, both alkaline phosphatase (ALP) activity and calcium deposition were distinctly enhanced at levels that were proportional to the quantity of osteoblasts in the culture. The increases in mRNA expression and ALP activity were greater in co-cultures treated with osteogenic supplements than in untreated cultures. However, the production of ALP activity followed by a distinct matrix mineralization was lower in osteogenic-treated cultures containing greater numbers of osteoblasts. This suggests that a higher density of osteoblasts may lead to weak osteogenesis of MSCs by direct cell–cell contact co-culture in an untreated environment. Furthermore, additional osteogenic supplements may act synergistically with osteoblasts to accelerate matrix mineralization by reducing the process of osteogenic differentiation in osteogenic treated co-cultures.
The present work may improve the understanding of MSC osteogenesis and may provide benefits for regenerative medicine.
PMCID: PMC3251672  PMID: 21567150
19.  Isolation and characterization of canine umbilical cord blood-derived mesenchymal stem cells 
Journal of Veterinary Science  2009;10(3):181-187.
Human umbilical cord blood-derived mesenchymal stem cells (MSCs) are known to possess the potential for multiple differentiations abilities in vitro and in vivo. In canine system, studying stem cell therapy is important, but so far, stem cells from canine were not identified and characterized. In this study, we successfully isolated and characterized MSCs from the canine umbilical cord and its fetal blood. Canine MSCs (cMSCs) were grown in medium containing low glucose DMEM with 20% FBS. The cMSCs have stem cells expression patterns which are concerned with MSCs surface markers by fluorescence-activated cell sorter analysis. The cMSCs had multipotent abilities. In the neuronal differentiation study, the cMSCs expressed the neuronal markers glial fibrillary acidic protein (GFAP), neuronal class III β tubulin (Tuj-1), neurofilament M (NF160) in the basal culture media. After neuronal differentiation, the cMSCs expressed the neuronal markers Nestin, GFAP, Tuj-1, microtubule-associated protein 2, NF160. In the osteogenic & chondrogenic differentiation studies, cMSCs were stained with alizarin red and toluidine blue staining, respectively. With osteogenic differentiation, the cMSCs presented osteoblastic differentiation genes by RT-PCR. This finding also suggests that cMSCs might have the ability to differentiate multipotentially. It was concluded that isolated MSCs from canine cord blood have multipotential differentiation abilities. Therefore, it is suggested that cMSCs may represent a be a good model system for stem cell biology and could be useful as a therapeutic modality for canine incurable or intractable diseases, including spinal cord injuries in future regenerative medicine studies.
PMCID: PMC2801133  PMID: 19687617
canine umbilical cord blood; differentiation study; mesenchymal stem cell; stem cell characterization
20.  Nicotine Deteriorates the Osteogenic Differentiation of Periodontal Ligament Stem Cells through α7 Nicotinic Acetylcholine Receptor Regulating wnt Pathway 
PLoS ONE  2013;8(12):e83102.
Cigarette smoking is one of the high risk factors of adult chronic periodontitis and nicotine is the well established toxic substance in cigarette. However, the mechanism of nicotine induced periodontitis is still unknown. Here we studied whether nicotine impaired the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) through activating α7 nicotinic acetylcholine receptor (α7 nAChR).
hPDLSCs with multi differentiation potential and surface makers for mesenchymal stem cells were harvested by limiting dilution technique. The level of mineralized nodule formation was assessed by alizarin red S staining. Expression level of ostegenic related genes and proteins were detected by real-time PCR and western blot analysis. The expression of α7 nAChR and its downstream signaling pathway were examined by western blot. The role of the receptor and related signaling pathway in nicotine impairing the osteogenic potential of hPDLSCs were also studied in different levels.
Nicotine deteriorated the ostegenic differentiation of hPDLSCs in a dose dependent manner. Activation of α7 nAChR by nicotine treatment activated wnt/β-catenin signaling pathway, leading to osteogenic deficiency of hPDLSCs. Blockage of α7 nAChR and wnt pathway inhibitor treatment rescued nicotine induced osteogenic differentiation deficiency.
These data suggested that nicotine activated α7 nAChR expressed on PDLSCs and further activated wnt signaling downstream, thus deteriorating the osteogenic potential of PDLSCs. The impairment of osteogenic differentiation of PDLSCs by nicotine might lead to cigarette smoking related periodontitis.
PMCID: PMC3869757  PMID: 24376645
21.  Osteogenic differentiation of amniotic epithelial cells: synergism of pulsed electromagnetic field and biochemical stimuli 
Pulsed electromagnetic field (PEMF) is a non-invasive physical therapy used in the treatment of fracture nonunion or delayed healing. PEMF can facilitate the osteogenic differentiation of bone marrow mesenchymal stem cells in vitro. Amniotic epithelial cells (AECs) have been proposed as a potential source of stem cells for cell therapy. However, whether PEMF could modulate the osteogenic differentiation of AECs is unknown. In the present study, the effects of PEMF on the osteogenic differentiation of AECs were investigated.
AECs were isolated from amniotic membrane of human placenta by trypsin digestion and were induced by PEMF and/or osteo-induction medium. After 21 days we used real time RT-PCR and immunocytochemistry to study the expression of osteoblast markers. The signal transduction of osteogenesis was further investigated.
The PEMF stimulation, or osteo-induction medium alone could induce osteogenic differentiation of AECs, as shown by expression of osteoblast specific genes and proteins including alkaline phosphatase and osteocalcin. Furthermore, a combination of PEMF and osteo-induction medium had synergy effects on osteogenic differentiation. In our study, the gene expression of BMP-2, Runx2, β-catenin, Nrf2, Keap1 and integrinβ1 were up-regulated in the osteogenic differentiation of AECs induced by PEMF and/or osteo-induction medium.
Combined application of PEMF and osteo-induction medium is synergistic for the osteogenic differentiation of AECs. It might be a novel approach in the bone regenerative medicine.
PMCID: PMC4267405  PMID: 25112311
Amniotic epithelial cells; Osteogenic differentiation; Pulsed electromagnetic field; BMP-2; Wnt/β-catenin signaling; Reactive oxygen species; Integrinβ1
22.  Inhibition of ERK Promotes Collagen Gel Compaction and Fibrillogenesis to Amplify the Osteogenesis of Human Mesenchymal Stem Cells in Three Dimensional, Collagen I Culture 
Stem cells and development  2009;18(2):331-341.
Tissue morphogenesis remains one of the least understood problems in cell and developmental biology. There is a disconnect between the mechanisms that apply to two dimensional (2D) cultures and those seen in vivo. Three dimensional (3D) culture presents a complex stimulus triggering cellular responses that are only partially understood. We compared 2D and 3D cultures of human mesenchymal stem cells in the presence of the MEK inhibitor, PD98059, to determine the role of ERK in collagen induced differentiation. 3D collagen I culture enhanced and accelerated the osteogenic differentiation of human mesenchymal stem cells. Contrary to 2D results, the addition of PD98059 induced a significant amplification of osteogenic gene expression and matrix mineralization in 3D cultures. The inhibition of ERK altered cell-mediated compaction, proliferation and resulted in the development of distinct tissue microstructure. Therefore, we suggest that the ability to reorganize collagen in 3D is an important step in ERK mediated osteogenic differentiation. This work aims to propose a correlation between osteogenic differentiation and hMSC directed collagen I remodeling. We present a potential mechanistic link (ERK) through which the three dimensionality of an engineered tissue acts to differentially induce and maintain cellular phenotype during tissue development.
PMCID: PMC2656582  PMID: 18491946
adult stem cells; collagen; differentiation; osteogenesis; matrix signaling
23.  Cyclic Tensile Strain Enhances Osteogenesis and Angiogenesis in Mesenchymal Stem Cells from Osteoporotic Donors 
Tissue Engineering. Part A  2013;20(1-2):67-78.
We have shown that the uniaxial cyclic tensile strain of magnitude 10% promotes and enhances osteogenesis of human mesenchymal stem cells (hMSC) and human adipose-derived stem cells (hASC) from normal, nonosteoporotic donors. In the present study, MSC from osteoporotic donors were analyzed for changes in mRNA expression in response to 10% uniaxial tensile strain to identify potential mechanisms underlying the use of this mechanical loading paradigm for prevention and treatment of osteoporosis. Human MSC isolated from three female, postmenopausal osteoporotic donors were analyzed for their responses to mechanical loading using microarray analysis of over 47,000 gene probes. Human MSC were seeded in three-dimensional collagen type I constructs to mimic the organic extracellular matrix of bone and 10% uniaxial cyclic tensile strain was applied to promote osteogenesis. Seventy-nine genes were shown to be regulated within hMSC from osteoporotic donors in response to 10% cyclic tensile strain. Upregulation of six genes were further confirmed with real-time RT-PCR: jun D proto-oncogene (JUND) and plasminogen activator, urokinase receptor (PLAUR), two genes identified as potential key molecules from network analysis; phosphoinositide-3-kinase, catalytic, delta polypeptide (PIK3CD) and wingless-type MMTV integration site family, member 5B (WNT5B), two genes with known importance in bone biology; and, PDZ and LIM domain 4 (PDLIM4) and vascular endothelial growth factor A (VEGFA), two genes that we have previously shown are significantly regulated in hASC in response to this mechanical stimulus. Function analysis indicated that 10% cyclic tensile strain induced expression of genes associated with cell movement, cell proliferation, and tissue development, including development in musculoskeletal and cardiovascular systems. Our results demonstrate that hMSC from aged, osteoporotic donors are capable of enhanced osteogenic differentiation in response to 10% cyclic tensile strain with significant increases in the expression of genes associated with enhanced cell proliferation, musculoskeletal development, and angiogenesis. Surprisingly, cyclic tensile strain of magnitude 10% not only enhanced osteogenesis in hMSC from osteoporotic donors, but also enhanced expression of angiogenic factors. Better understanding and methodologies to promote osteogenesis in hMSC from elderly, osteoporotic donors may greatly facilitate achieving long-term success in bone regeneration and functional bone tissue engineering for this ever-growing patient population.
PMCID: PMC3875187  PMID: 23927731
24.  Utilization of transgenic models in evaluation of osteogenic differentiation of embryonic stem cells 
Connective tissue research  2013;54(0):296-304.
Previous studies reported that embryonic stem cells (ESCs) can be induced to differentiate into cells showing a mature osteoblastic phenotype by culturing them under osteo-inductive conditions. It is probable that osteogenic differentiation requires that ESCs undergo differentiation through an intermediary step involving a mesenchymal lineage precursor. Based on our previous studies indicating that adult mesenchymal progenitor cells express αSMA, we have generated ESCs from transgenic mice in which an αSMA promoter directs the expression of red fluorescent protein (RFP) to mesenchymal progenitor cells. To track the transition of ESC-derived MSCs into mature osteoblasts, we have utilized a bone-specific fragment of rat type I collagen promoter driving green fluorescent protein (Col2.3GFP).
Following osteogenic induction in ESCs, we have observed expression of alkaline phosphatase and subsequent mineralization as detected by von Kossa staining. After one week of osteogenic induction, ESCs begin to express αSMARFP. This expression was localized to the peripheral area encircling a typical ESC colony. Nevertheless, these αSMARFP positive cells did not show activation of the Col2.3GFP promoter, even after 7 weeks of osteogenic differentiation in vitro. In contrast, Col2.3GFP expression was detected in vivo, in mineralized areas following teratoma formation.
Our results indicate that detection of alkaline phosphatase activity and mineralization of ESCs cultured under osteogenic conditions is not sufficient to demonstrate osteogenic maturation. Our study indicates the utility of the promoter-visual transgene approach to assess the commitment and differentiation of ESCs into the osteoblast lineage.
PMCID: PMC3893759  PMID: 23782451
Embryonic stem cells; mesenchymal stem cells; differentiation; osteogenesis; GFP; teratoma
25.  Synergistic effect of recombinant human bone morphogenic protein-7 and osteogenic differentiation medium on human bone-marrow-derived mesenchymal stem cells in vitro 
International Orthopaedics  2011;35(12):1889-1895.
The purpose of this study was to investigate the effect of recombinant human bone morphogenetic protein-7 (rhBMP-7) with or without osteogenic differentiation medium (ODM) on osteogenic differentiation of primary human bone-marrow-derived mesenchymal stem cells (hBMSCs) in vitro.
The hBMSCs were isolated from medullary reaming tissue. At 80% confluence, hBMSCs were treated with different concentrations of rhBMP-7 with and without ODM. Alkaline phosphatase (ALP) activity, calcium deposition and messenger RNA (mRNA) expression of osteocalcin (OC) and osteopontin (OPN) were examined.
ALP activity and calcium deposits in hBMSC culture were significantly increased by rhBMP-7 at 0.1 μg/ml (0.23 ± 0.07 IU and 28.9 ± 4.2 mg/dl) and 1.0 μg/ml (0.32 ± 0.03 IU and 38.7 ± 3.0 mg/dl), respectively, in the presence of ODM, showing a clearly dose-dependent osteoblastic differentiation. However, the same dose of 0.1 μg/ml rhBMP-7 without ODM and ODM alone induced low level of ALP and calcium deposits, indicating a synergistic effect of rhBMP-7 and ODM on committed osteogenic differentiation. Quantitative real-time reverse-transcriptase polymerase chain reaction (RT-PCR) analysis showed up-regulated OC and OPN mRNA levels, corroborating the synergistic effect of rhBMP-7 and ODM.
Our study showed that rhBMP-7 with ODM created a synergistic effect on up-regulation of osteogenic genes as well as osteogenic differentiation of primary hBMSCs in vitro. In the presence of ODM, the lowest concentration of rhBMP-7 needed to induce significant osteogenic differentiation of hBMSCs was 0.1 μg/ml.
PMCID: PMC3224605  PMID: 21487672

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