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1.  Gravity, a regulation factor in the differentiation of rat bone marrow mesenchymal stem cells 
Stem cell therapy has emerged as a potential therapeutic option for tissue engineering and regenerative medicine, but many issues remain to be resolved, such as the amount of seed cells, committed differentiation and the efficiency. Several previous studies have focused on the study of chemical inducement microenvironments. In the present study, we investigated the effects of gravity on the differentiation of bone marrow mesenchymal stem cells (BMSCs) into force-sensitive or force-insensitive cells.
Methods and results
Rat BMSCs (rBMSCs) were cultured under hypergravity or simulated microgravity (SMG) conditions with or without inducement medium. The expression levels of the characteristic proteins were measured and analyzed using immunocytochemical, RT-PCR and Western-blot analyses. After treatment with 5-azacytidine and hypergravity, rBMSCs expressed more characteristic proteins of cardiomyocytes such as cTnT, GATA4 and β-MHC; however, fewer such proteins were seen with SMG. After treating rBMSCs with osteogenic inducer and hypergravity, there were marked increases in the expression levels of ColIA1, Cbfa1 and ALP. Reverse results were obtained with SMG. rBMSCs treated with adipogenic inducer and SMG expressed greater levels of PPARgamma. Greater levels of Cbfa1- or cTnT-positive cells were observed under hypergravity without inducer, as shown by FACS analysis. These results indicate that hypergravity induces differentiation of rBMSCs into force-sensitive cells (cardiomyocytes and osteoblasts), whereas SMG induces force-insensitive cells (adipocytes).
Taken together, we conclude that gravity is an important factor affecting the differentiation of rBMSCs; this provides a new avenue for mechanistic studies of stem cell differentiation and a new approach to obtain more committed differentiated or undifferentiated cells.
PMCID: PMC2754420  PMID: 19772591
2.  Investigating the Role of FGF18 in the Cultivation and Osteogenic Differentiation of Mesenchymal Stem Cells 
PLoS ONE  2012;7(8):e43982.
Fibroblast growth factor18 (FGF18) belongs to the FGF family and is a pleiotropic protein that stimulates proliferation in several tissues. Bone marrow mesenchymal stem cells (BMSCs) participate in the normal replacement of damaged cells and in disease healing processes within bone and the haematopoietic system. In this study, we constructed FGF18 and investigated its effects on rat BMSCs (rBMSCs). The proliferative effects of FGF18 on rBMSCs were examined using an MTS assay. To validate the osteogenic differentiation effects of FGF18, ALP and mineralization activity were examined as well as osteogenic differentiation-related gene levels. FGF18 significantly enhanced rBMSCs proliferation (p<0.001) and induced the osteogenic differentiation by elevating ALP and mineralization activity of rBMSCs (p<0.001). Furthermore, these osteogenic differentiation effects of FGF18 were confirmed via increasing the mRNA levels of collagen type I (Col I), bone morphogenetic protein 4 (BMP4), and Runt-related transcription factor 2 (Runx2) at 3 and 7 days. These results suggest that FGF18 could be used to improve bone repair and regeneration.
PMCID: PMC3427245  PMID: 22937141
3.  Temporal Expression of Pelp1 during Proliferation and Osteogenic Differentiation of Rat Bone Marrow Mesenchymal Stem Cells 
PLoS ONE  2013;8(10):e75477.
Osteogenic induction and bone formation are heavily affected by environmental factors, including estrogen, estrogen receptors, and coregulatory proteins, such as the recently reported proline-, glutamic acid-, and leucine-rich protein 1(Pelp1).
To investigate Pelp1 expression in rat bone mesenchymal stem cells (rBMSCs) during cell proliferation and osteogenic differentiation.
rBMSCs were cultured in routine and osteogenic differentiation media. Cell proliferation was assessed at days 1, 3, 5, 7, 9, 11, 14, and 21. Pelp1 protein expression in the nucleus and cytoplasm were detected by immunocytochemical analysis. Real-time RT-PCR and western blot were used to detect mRNA and protein expressions of Pelp1, osteocalcin (OCN), and alkaline phosphatase (ALP).
Over 21 days, rBMSCs in routine culture exhibited a 1-2 day lag phase and exponential growth from day 3 to 9, plateauing at day 9, and correlated with temporal mRNA expression of Pelp1, which almost reached baseline levels at day 21. In osteogenic induction cultures, Pelp1 mRNA levels rose at day 9 and steadily increased until day 21, reaching 6.8-fold greater value compared with day 1. Interestingly, Pelp1 mRNA expression in osteogenic cultures exhibited a trend similar to that of OCN expression. Pelp1 knockdown by siRNA transfection inhibited undifferentiated rBMSC proliferation, and bone markers OCN and ALP expressions in rBMSCs cultured in routine and osteogenic differentiation media.
Pelp1 may be a key player in BMSCs proliferation and osteogenic differentiation, meriting further consideration as a target for development of therapies for pathological bone loss conditions, such as menopausal bone loss.
PMCID: PMC3797710  PMID: 24146754
4.  Simulated microgravity facilitates cell migration and neuroprotection after bone marrow stromal cell transplantation in spinal cord injury 
Recently, cell-based therapy has gained significant attention for the treatment of central nervous system diseases. Although bone marrow stromal cells (BMSCs) are considered to have good engraftment potential, challenges due to in vitro culturing, such as a decline in their functional potency, have been reported. Here, we investigated the efficacy of rat BMSCs (rBMSCs) cultured under simulated microgravity conditions, for transplantation into a rat model of spinal cord injury (SCI).
rBMSCs were cultured under two different conditions: standard gravity (1G) and simulated microgravity attained by using the 3D-clinostat. After 7 days of culture, the rBMSCs were analyzed morphologically, with RT-PCR and immunostaining, and were used for grafting. Adult rats were used for constructing SCI models by using a weight-dropping method and were grouped into three experimental groups for comparison. rBMSCs cultured under 1 g and simulated microgravity were transplanted intravenously immediately after SCI. We evaluated the hindlimb functional improvement for 3 weeks. Tissue repair after SCI was examined by calculating the cavity area ratio and immunohistochemistry.
rBMSCs cultured under simulated microgravity expressed Oct-4 and CXCR4, in contrast to those cultured under 1 g conditions. Therefore, rBMSCs cultured under simulated microgravity were considered to be in an undifferentiated state and thus to possess high migration ability. After transplantation, grafted rBMSCs cultured under microgravity exhibited greater survival at the periphery of the lesion, and the motor functions of the rats that received these grafts improved significantly compared with the rats that received rBMSCs cultured in 1 g. In addition, rBMSCs cultured under microgravity were thought to have greater trophic effects on reestablishment and survival of host spinal neural tissues because cavity formations were reduced, and apoptosis-inhibiting factor expression was high at the periphery of the SCI lesion.
Here we show that transplantation of rBMSCs cultured under simulated microgravity facilitates functional recovery from SCI rather than those cultured under 1 g conditions.
PMCID: PMC3706926  PMID: 23548163
Bone marrow stromal cell; Migration; Simulated microgravity; Spinal cord injury; Survival; Trophic factor
5.  Self-Assembling Peptide Hydrogels Modulate In Vitro Chondrogenesis of Bovine Bone Marrow Stromal Cells 
Tissue Engineering. Part A  2009;16(2):465-477.
Our objective was to test the hypothesis that self-assembling peptide hydrogel scaffolds provide cues that enhance the chondrogenic differentiation of bone marrow stromal cells (BMSCs). BMSCs were encapsulated within two unique peptide hydrogel sequences, and chondrogenesis was compared with that in agarose hydrogels. BMSCs in all three hydrogels underwent transforming growth factor-β1-mediated chondrogenesis as demonstrated by comparable gene expression and biosynthesis of extracellular matrix molecules. Expression of an osteogenic marker was unchanged, and an adipogenic marker was suppressed by transforming growth factor-β1 in all hydrogels. Cell proliferation occurred only in the peptide hydrogels, not in agarose, resulting in higher glycosaminoglycan content and more spatially uniform proteoglycan and collagen type II deposition. The G1-positive aggrecan produced in peptide hydrogels was predominantly the full-length species, whereas that in agarose was predominantly the aggrecanase product G1-NITEGE. Unique cell morphologies were observed for BMSCs in each peptide hydrogel sequence, with extensive cell–cell contact present for both, whereas BMSCs in agarose remained rounded over 21 days in culture. Differences in cell morphology within the two peptide scaffolds may be related to sequence-specific cell adhesion. Taken together, this study demonstrates that self-assembling peptide hydrogels enhance chondrogenesis compared with agarose as shown by extracellular matrix production, DNA content, and aggrecan molecular structure.
PMCID: PMC2862611  PMID: 19705959
6.  Bone Morphogenetic Protein Receptor in the Osteogenic Differentiation of Rat Bone Marrow Stromal Cells 
Yonsei Medical Journal  2010;51(5):740-745.
Several signaling pathways have been shown to regulate the lineage commitment and terminal differentiation of bone marrow stromal cells (BMSCs). Bone morphogenetic protein (BMP) signaling has important effects on the process of skeletogenesis. In the present study, we tested the role of bone morphogenetic protein receptor (BMPR) in the osteogenic differentiation of rat bone marrow stromal cells in osteogenic medium (OM) with or without BMP-2.
Materials and Methods
BMSCs were harvested from rats and cultured in OM containing dexamethasone, β-glycerophosphate, and ascorbic acid, with or without BMP-2 in order to induce osteogenic differentiation. The alkaline phosphatase (ALP) activity assay and von kossa staining were used to assess the osteogenic differentiation of the BMSCs. BMPR mRNA expression was assessed using reverse transcription-polymerase chain reaction (RT-PCR).
The BMSCs that underwent osteogenic differentiation in OM showed a higher level of ALP activity and matrix mineralization. BMP-2 alone induced a low level of ALP activity and matrix mineralization in BMSCs, but enhanced the osteogenic differentiation of BMSCs when combined with OM. The OM significantly induced the expression of type IA receptor of BMPR (BMPRIA) and type II receptor of BMPR (BMPRII) in BMSCs after three days of stimulation, while BMP-2 significantly induced BMPRIA and BMPRII in BMSCs after nine or six days of stimulation, respectively.
BMSCs commit to osteoblastic differentiation in OM, which is enhanced by BMP-2. In addition, BMP signaling through BMPRIA and BMPRII regulates the osteogenic differentiation of rat BMSCs in OM with or without BMP-2.
PMCID: PMC2908870  PMID: 20635450
Bone marrow stromal cells; osteogenesis; differentiation; bone morphogenetic protein receptor
7.  Effect of Hydrogel Porosity on Marrow Stromal Cell Phenotypic Expression 
Biomaterials  2008;29(14):2193-2202.
This study describes investigation of porous photocrosslinked oligo[(polyethylene glycol) fumarate] (OPF) hydrogels as potential matrix for osteoblastic differentiation of marrow stromal cells (MSCs). The porosity and interconnectivity of porous hydrogels were assessed using magnetic resonance microscopy (MRM) as a noninvasive investigative tool that could image the water construct inside the hydrogels at a high spatial resolution. MSCs were cultured onto the porous hydrogels and cell number was assessed using PicoGreen DNA assay. Our results showed 10% of cells initially attached to the surface of scaffolds. However, cells did not show significant proliferation over a time period of 14 days. MSCs cultured on porous hydrogels had increased alkaline phosphatase activity as well as deposition of calcium, suggesting successful differentiation and maturation to the osteoblastic phenotype. Moreover, continued expression of type I collagen and osteonectin over 14 days confirmed osteoblastic differentiation of MSCs. MRM was also applied to monitor osteogenesis of MSCs on porous hydrogels. MRM images showed porous scaffolds became consolidated with osteogenic progression of cell differentiation. These findings indicate that porous OPF scaffolds enhanced MSC differentiation leading to development of bone-like mineralized tissue.
PMCID: PMC2386206  PMID: 18262642
Hydrogel; oligo[(polyethylene glycol) fumarate] (OPF); Marrow stromal cells; Magnetic resonance microscopy; Osteogenesis
8.  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
9.  Effect of Cyclic Strain on Cardiomyogenic Differentiation of Rat Bone Marrow Derived Mesenchymal Stem Cells 
PLoS ONE  2012;7(4):e34960.
Mesenchymal stem cells (MSCs) are a potential source of material for the generation of tissue-engineered cardiac grafts because of their ability to transdifferentiate into cardiomyocytes after chemical treatments or co-culture with cardiomyocytes. Cardiomyocytes in the body are subjected to cyclic strain induced by the rhythmic heart beating. Whether cyclic strain could regulate rat bone marrow derived MSC (rBMSC) differentiation into cardiomyocyte-like lineage was investigated in this study. A stretching device was used to generate the cyclic strain for rBMSCs. Cardiomyogenic differentiation was evaluated using quantitative real-time reverse transcription polymerase chain reaction (RT-PCR), immunocytochemistry and western-blotting. The results demonstrated that appropriate cyclic strain treatment alone could induce cardiomyogenic differentiation of rBMSCs, as confirmed by the expression of cardiomyocyte-related markers at both mRNA and protein levels. Furthermore, rBMSCs exposed to the strain stimulation expressed cardiomyocyte-related markers at a higher level than the shear stimulation. In addition, when rBMSCs were exposed to both strain and 5-azacytidine (5-aza), expression levels of cardiomyocyte-related markers significantly increased to a degree suggestive of a synergistic interaction. These results suggest that cyclic strain is an important mechanical stimulus affecting the cardiomyogenic differentiation of rBMSCs. This provides a new avenue for mechanistic studies of stem cell differentiation and a new approach to obtain more committed differentiated cells.
PMCID: PMC3319595  PMID: 22496879
10.  Comparison of Potentials of Stem Cells Isolated from Tendon and Bone Marrow for Musculoskeletal Tissue Engineering 
Tissue Engineering. Part A  2011;18(7-8):840-851.
The use of tendon-derived stem cells (TDSCs) as a cell source for musculoskeletal tissue engineering has not been compared with that of bone marrow stromal cells (BMSC). This study compared the mesenchymal stem cell (MSC) and embryonic stem cells (ESC) markers, clonogenicity, proliferative capacity, and multilineage differentiation potential of rat TDSC and BMSC in vitro. The MSC and ESC marker profiles of paired TDSC and BMSC were compared using flow cytometry and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Their clonogenicity and proliferative capacity were compared using colony-forming and 5-bromo-2′-deoxyuridine assays, respectively. The expression of tenogenic, osteogenic, and chondrogenic markers at basal state were examined using qRT-PCR. Their osteogenic, chondrogenic, and adipogenic differentiation potentials were compared using standard assays. TDSC and BMSC showed similar expression of CD90 and CD73. TDSC expressed higher levels of Oct4 than BMSC. TDSC exhibited higher clonogenicity, proliferated faster, and expressed higher tenomodulin, scleraxis, collagen 1 α 1 (Col1A1), decorin, alkaline phosphatase, Col2A1, and biglycan messenger RNA levels than BMSC. There was higher calcium nodule formation and osteogenic marker expression in TDSC than BMSC upon osteogenic induction. More chondrocyte-like cells and higher glycosaminoglycan deposition and chondrogenic marker expression were observed in TDSC than BMSC upon chondrogenic induction. There were more oil droplets and expression of an adipogenic marker in TDSC than BMSC upon adipogenic induction. TDSC expressed higher Oct4 levels, which was reported to positively regulate mesendodermal lineage differentiation, showed higher clonogenicity and proliferative capacity, and had greater tenogenic, osteogenic, chondrogenic, and adipogenic markers and differentiation potential than BMSC. TDSC might be a better cell source than BMSC for musculoskeletal tissue regeneration.
PMCID: PMC3313612  PMID: 22011320
11.  A fibrin/hyaluronic acid hydrogel for the delivery of mesenchymal stem cells and potential for articular cartilage repair 
Osteoarthritis (OA) is a degenerative joint disease affecting approximately 27 million Americans, and even more worldwide. OA is characterized by degeneration of subchondral bone and articular cartilage. In this study, a chondrogenic fibrin/hyaluronic acid (HA)-based hydrogel seeded with bone marrow-derived mesenchymal stem cells (BMSCs) was investigated as a method of regenerating these tissues for OA therapy. This chondrogenic hydrogel system can be delivered in a minimally invasive manner through a small gauge needle, forming a three-dimensional (3D) network structure in situ. However, an ongoing problem with fibrin/HA-based biomaterials is poor mechanical strength. This was addressed by modifying HA with methacrylic anhydride (MA) (HA-MA), which reinforces the fibrin gel, thereby improving mechanical properties. In this study, a range of fibrinogen (the fibrin precursor) and HA-MA concentrations were explored to determine optimal conditions for increased mechanical strength, BMSC proliferation, and chondrogenesis potential in vitro.
Increased mechanical strength was achieved by HA-MA reinforcement within fibrin hydrogels, and was directly correlated with increasing HA-MA concentration. Live/dead staining and metabolic assays confirmed that the crosslinked fibrin/HA-MA hydrogels provided a suitable 3D environment for BMSC proliferation. Quantitative polymerase chain reaction (qPCR) of BMSCs incubated in the fibrin/HA-MA hydrogel confirmed decreased expression of collagen type 1 alpha 1 mRNA with an increase in Sox9 mRNA expression especially in the presence of a platelet lysate, suggesting early chondrogenesis.
Fibrin/HA-MA hydrogel may be a suitable delivery method for BMSCs, inducing BMSC differentiation into chondrocytes and potentially aiding in articular cartilage repair for OA therapy.
PMCID: PMC4109069  PMID: 25061479
Osteoarthritis; Fibrin; Hyaluronic acid; Mesenchymal stem cell; Hydrogel; Cartilage; Stem cell delivery; Regenerative medicine; Tissue engineering
12.  Dual Delivery of BMP-2 and bFGF from a New Nano-Composite Scaffold, Loaded with Vascular Stents for Large-Size Mandibular Defect Regeneration 
The aim of this study was to investigate the feasibility and advantages of the dual delivery of bone morphogenetic protein-2 (BMP-2) and basic fibroblast growth factor (bFGF) from nano-composite scaffolds (PLGA/PCL/nHA) loaded with vascular stents (PLCL/Col/nHA) for large bone defect regeneration in rabbit mandibles. Thirty-six large bone defects were repaired in rabbits using engineering bone composed of allogeneic bone marrow mesenchymal stem cells (BMSCs), bFGF, BMP-2 and scaffolds composed of PLGA/PCL/nHA loaded with PLCL/Col/nHA. The experiments were divided into six groups: BMSCs/bFGF/BMP-2/scaffold, BMSCs/BMP-2/scaffold, BMSCs/bFGF/scaffold, BMSCs/scaffold, scaffold alone and no treatment. Sodium alginate hydrogel was used as the carrier for BMP-2 and bFGF and its features, including gelling, degradation and controlled release properties, was detected by the determination of gelation and degradation time coupled with a controlled release study of bovine serum albumin (BSA). AlamarBlue assay and alkaline phosphatase (ALP) activity were used to evaluate the proliferation and osteogenic differentiation of BMSCs in different groups. X-ray and histological examinations of the samples were performed after 4 and 12 weeks post-implantation to clarify new bone formation in the mandible defects. The results verified that the use of sodium alginate hydrogel as a controlled release carrier has good sustained release ability, and the combined application of bFGF and BMP-2 could significantly promote the proliferation and osteogenic differentiation of BMSCs (p < 0.05 or p < 0.01). In addition, X-ray and histological examinations of the samples exhibited that the dual release group had significantly higher bone formation than the other groups. The above results indicate that the delivery of both growth factors could enhance new bone formation and vascularization compared with delivery of BMP-2 or bFGF alone, and may supply a promising way of repairing large bone defects in bone tissue engineering.
PMCID: PMC3709809  PMID: 23778088
bone morphogenetic protein-2; basic fibroblast growth factor; tissue engineering; bone defect; poly(lactic-co-glycolic acid); polycaprolactone; hydroxyapatite
13.  Potential of Hydrogels Based on Poly(Ethylene Glycol) and Sebacic Acid as Orthopedic Tissue Engineering Scaffolds 
Tissue Engineering. Part A  2009;15(8):2299-2307.
In this study, the bioactive effects of poly(ethylene glycol) (PEG) sebacic acid diacrylate (PEGSDA) hydrogels with or without RGD peptide modification on osteogenic differentiation and mineralization of marrow stromal cells (MSCs) were examined. In a separate experiment, the ability of PEGSDA hydrogel to serve as a delivery vehicle for bone morphogenetic protein 2 (BMP-2) was also investigated. As a scaffold, the attachment and proliferation of MSCs on PEGSDA hydrogel scaffolds with and without RGD peptide modification was similar to the control, tissue culture polystyrene. In contrast, cells were barely seen on unmodified PEG diacrylate (PEGDA) hydrogel throughout the culture period for up to 21 days. Osteogenic phenotypic expression such as alkaline phosphatase (ALP) of MSCs as well as mineralized calcium content were significantly higher on PEGSDA-based hydrogels than those on the control or PEGDA hydrogels. Potential use of PEGSDA scaffold as a delivery vehicle of osteogenic molecules such as BMP-2 was also evaluated. Initial burst release of BMP-2 from PEGSDA hydrogel scaffold (14.7%) was significantly reduced compared to PEGDA hydrogel scaffold (84.2%) during the first 3 days of a 21-day release period. ALP activity of an osteoblast was significantly higher in the presence of BMP-2 released from PEGSDA hydrogel scaffolds compared to that in the presence of BMP-2 released from PEGDA scaffolds, especially after 6 days of release. Overall, PEGSDA hydrogel scaffolds without further modification may be useful as orthopedic tissue engineering scaffolds as well as local drug carriers for prolonged sustained release of osteoinductive molecules.
PMCID: PMC2792107  PMID: 19292677
14.  Osterix Overexpression in Mesenchymal Stem cells Stimulates Healing of Critical-Sized Defects in Murine Calvarial Bone 
Tissue engineering  2007;13(10):2431-2440.
Osterix (Osx) is a zinc-finger-containing transcription factor that is expressed in osteoblasts of all endochondral and membranous bones. In Osx null mice, osteoblast differentiation is impaired, and bone formation is absent. We hypothesized that overexpression of Osx in bone marrow–derived mesenchymal stem cells (BMSCs) would enhance osteogenic differentiation during bone regeneration in vivo. Overexpression of Osx in mouse BMSCs was achieved using retroviral infection together with a green fluorescent protein (GFP) vector to monitor transduction efficiency and determine the source of regenerative cells in implantation studies. Bone regeneration in vivo was evaluated by implanting BMSCs overexpressing Osx into 4-mm calvarial bone defects in adult mice using type I collagen sponge as a carrier. New bone formation in the defects was quantified using radiological and histological procedures 5 weeks after implantation. The results showed that implantation of Osx-transduced BMSCs resulted in 85% healing of calvarial bone defects as detected using radiological analyses. Histological examination of the implants demonstrated that the Osx-transduced group exhibited amounts of newly formed bone that was five times as high as in a group transduced with the empty vector. Immunohistochemistry for GFP showed positive immunoreaction localized to areas of newly engineered bone in the Osx-transduced group. Immunohistochemistry with antibodies against the extracellular matrix protein bone sialoprotein resulted in strong staining in areas of new bone formation. In addition, the clonal BMSCs showed an osteogenic potential similar to that of primary cultures of BMSCs, suggesting the usefulness of this model in bone tissue engineering. These results indicate that ex vivo gene therapy of Osx is a useful therapeutic approach in regenerating adult bone tissue.
PMCID: PMC2835465  PMID: 17630878
15.  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
16.  Enhanced migration of human bone marrow stromal cells in modified collagen hydrogels 
International Orthopaedics  2013;37(8):1605-1611.
Collagen I hydrogels are widely used as scaffolds for regeneration of articular cartilage defects. We hypothesised that ingrowth might be improved by removing the superficial layer of a compressed hydrogel. The control group consisted of the original unmodified product.
The migration of human bone marrow stromal cells (hBMSCs) into the hydrogel was evaluated by confocal microscopy. We quantified the DNA concentration of the hydrogel for each group and time point and evaluated the chondrogenic differentiation of cells.
After one week, the detectable amount of cells at the depth of 26–50 μm was significantly higher in the modified matrix (MM) than in the non-modified matrix (NM) (p = 0.011). The maximum depth of penetration was 75 μm (NM) and 200 μm (MM). After three weeks, the maximum depth of penetration was 175 μm (NM) and 200 μm (MM). Likewise, at a depth of 0–25 μm the amount of detectable cells was significantly higher in the MM group (p = 0.003). After 14 days, the concentration of DNA was significantly higher in the samples of the MM than in the control group (p = 0.000). Staining of histological sections and labelling with collagen II antibodies showed that a chondrogenic differentiation of cells in the scaffold can occur during in vitro cultivation.
Removing the superficial layer is essential to ensuring proper ingrowth of cells within the compressed hydrogel. Compressed hydrogels contribute better to cartilage regeneration after surface modification.
PMCID: PMC3728398  PMID: 23645081
17.  Designer Self-Assembling Peptide Nanofiber Scaffolds Containing Link Protein N-Terminal Peptide Induce Chondrogenesis of Rabbit Bone Marrow Stem Cells 
BioMed Research International  2014;2014:421954.
Designer self-assembling peptide nanofiber hydrogel scaffolds have been considered as promising biomaterials for tissue engineering because of their excellent biocompatibility and biofunctionality. Our previous studies have shown that a novel designer functionalized self-assembling peptide nanofiber hydrogel scaffold (RLN/RADA16, LN-NS) containing N-terminal peptide sequence of link protein (link N) can promote nucleus pulposus cells (NPCs) adhesion and three-dimensional (3D) migration and stimulate biosynthesis of type II collagen and aggrecan by NPCs in vitro. The present study has extended these investigations to determine the effects of this functionalized LN-NS on bone marrow stem cells (BMSCs), a potential cell source for NP regeneration. Although the functionalized LN-NS cannot promote BMSCs proliferation, it significantly promotes BMSCs adhesion compared with that of the pure RADA16 hydrogel scaffold. Moreover, the functionalized LN-NS remarkably stimulates biosynthesis and deposition of type II collagen and aggrecan. These data demonstrate that the functionalized peptide nanofiber hydrogel scaffold containing link N peptide as a potential matrix substrate will be very useful in the NP tissue regeneration.
PMCID: PMC4160642  PMID: 25243141
18.  Human Embryonic Stem Cells Undergo Osteogenic Differentiation in Human Bone Marrow Stromal Cell Microenvironments 
Journal of stem cells  2007;2(3):139-147.
Human embryonic stem cells (hESCs) may offer an unlimited supply of cells that can be directed to differentiate into all cell types within the body and used in regenerative medicine for tissue and cell replacement therapies. Previous work has shown that exposing hESCs to exogenous factors such as dexamethasone, ascorbic acid and β-glycerophosphate can induce osteogenesis. The specific factors that induce osteogenic differentiation of hESCs have not been identified yet, however, it is possible that differentiated human bone marrow stromal cells (hMBSCs) may secrete factors within the local microenvironment that promote osteogenesis. Here we report that the lineage progression of hESCs to osteoblasts is achieved in the presence of soluble signaling factors derived from differentiated hBMSCs. For 28 days, hESCs were grown in a transwell co-culture system with hBMSCs that had been previously differentiated in growth medium containing defined osteogenic supplements for 7-24 days. As a control. hESCs were co-cultured with undifferentiated hBMSCs and alone. Von Kossa and Alizarin Red staining as well as immunohistochemistry confirmed that the hESCs co-cultured with differentiated hBMSCs formed mineralized bone nodules and secreted extracellular matrix protein osteocalcin (OCN). Quantitative Alizarin Red assays showed increased mineralization as compared to the control with undifferentiated hBMSCs. RT-PCR revealed the loss of pluripotent hESC markers with the concomitant gain of osteoblastic markers such as collagen type I, runx2, and osterix. We demonstrate that osteogenic growth factors derived from differentiated hBMSCs within the local microenvironment may help to promote hESC osteogenic differentiation.
PMCID: PMC2910923  PMID: 20671800
Human embryonic stem cells; bone marrow stromal cells; osteoblasts; stem cell-microenvironment
19.  Transplanted xenogenic bone marrow stem cells survive and generate new bone formation in the posterolateral lumbar spine of non-immunosuppressed rabbits 
European Spine Journal  2008;17(11):1515-1521.
Bone marrow stem cells (BMSCs) are pluripotent cells that have been used to facilitate bone repair because of their capability of differentiating into osteoblasts. However, it is well known that the number of BMSCs with osteogenic potential decreases in patients with old age, osteoporosis, and metabolic diseases. In such conditions, xenogenic BMSCs may provide an alternative to autologous BMSCs. In the current study, we investigated the potential of transplanted xenogenic BMSCs to survive and generate new bone formation in the posterolateral lumbar spine of non-immunosuppressed rabbits. The BMSCs were obtained from bilateral femurs of four male rats, cultured and expanded in medium with osteoinduction supplement. The BMSCs (1,000,000 cells) of male rats loaded onto 5 cc compression resistant matrix (CRM; Medtronic Sofamor Danek, USA) were implanted bilaterally onto the L4-5 intertransverse processes of 16 female rabbits (xenogenic BMSCs + CRM group). The 16 female rabbits that received 5 cc CRM alone were used as controls (CRM alone group). To exclude the possibility of migration of BMSCs from the transverse processes of the recipient rabbits, we did not decorticate the transverse processes. No rabbits received any immunosuppressive medications during the experiment. Four rabbits each in both of the experimental and control groups were killed at 1, 2, 4, and 6 months postimplantation, and the lumbar spine underwent radiological and histological analyses for evaluation of new bone formation. The polymerase chain reaction (PCR) for Sry gene (Y-chromosome-specific marker) was used to evaluate the survival of transplanted xenogenic BMSCs. The expression of Sry gene was clearly identified in the lumbar spines of all the 16 rabbits in the xenogenic BMSCs + CRM group at 1–6 months postimplantation. Serial plain radiographs showed gradual resorption of CRM; however, it was difficult to clearly identify the presence of new bone formation due to the radiopacity of the remaining CRM. Histologically, mature lamellar and woven bone with osteoblasts and osteocytes were identified in all eight rabbits in the xenogenic BMSCs + CRM group at 4 and 6 months postimplantation, but in none of the eight rabbits at 1 and 2 months postimplantation. None of CRM alone group showed new bone formation at 1–6 months postimplantation. Mild-to-moderate infiltration of inflammatory cells was identified around the CRM carriers in both the groups. No post-operative wound infection was found in either group. Our results indicate that xenogenic BMSCs loaded onto CRM survive and generate new bone formation when placed into the posterolateral lumbar spine of rabbits without immunosuppression. To determine if a solid fusion can be achieved with such techniques, further studies are needed to investigate the appropriate dose of xenogenic BMSCs, amounts of CRM, and the requisite incubation time.
PMCID: PMC2583184  PMID: 18815818
Xenogenic bone marrow stem cells; Survival; Bone formation; Immune suppression; Posterolateral lumbar spine
20.  The role of osteoblast cells in the pathogenesis of unicameral bone cysts 
The pathogenesis of unicameral bone cysts (UBCs) remains largely unknown. Osteoclasts have been implicated, but the role of osteoblastic cells has, to date, not been explored. This study investigated the pathophysiology of UBCs by examining the interactions between the cyst fluid and human bone marrow stromal cells (hBMSCs) and the effect of the fluid on osteogenesis.
Fluid was aspirated from two UBCs and analysed for protein, electrolyte and cytokine levels. Graded concentrations of the fluid were used as culture media for hBMSCs to determine the effects of the fluid on hBMSC proliferation and osteogenic differentiation. The fibrocellular lining was analysed histologically and by electron microscopy.
Alkaline phosphatase (ALP) staining of hBMSCs that were cultured in cyst fluid demonstrated increased cell proliferation and osteogenic differentiation compared to basal media controls. Biochemical analysis of these hBMSCs compared to basal controls confirmed a marked increase in DNA content (as a marker of proliferation) and ALP activity (as a marker of osteogenic differentiation) which was highly significant (p < 0.001). Osteoclasts were demonstrated in abundance in the cyst lining. The cyst fluid cytokine profile revealed levels of the pro-osteoclast cytokines IL-6, MIP-1α and MCP-1 that were 19×, 31× and 35× greater than those in reference serum.
Cyst fluid promoted osteoblastic growth and differentiation. Despite appearing paradoxical that the cyst fluid promoted osteogenesis, osteoblastic cells are required for osteoclastogenesis through RANKL signalling. Three key cytokines in this pathway (IL-6, MIP-1α, MCP-1) were highly elevated in cyst fluid. These findings may hold the key to the pathogenesis of UBCs, with implications for treatment methods.
PMCID: PMC3425701  PMID: 23904902
Unicameral bone cyst; Osteoblast cell; Osteoclast; Cytokine; RANK ligand
21.  rhPDGF-BB Promotes Proliferation and Osteogenic Differentiation of Bone Marrow Stromal Cells from Streptozotocin-Induced Diabetic Rats through ERK Pathway 
BioMed Research International  2014;2014:637415.
Management of nonunion fracture and massive segmental bone defects in diabetes remains a challenging clinical problem. Bone marrow stromal cells (BMSCs) are crucial for bone remodeling and hold promise for bone regeneration. However, we have showed previously that diabetes can affect the proliferation and osteogenic potential of BMSCs adversely and a strategy to attenuate the impaired functions of BMSCs is required. Platelet-derived growth factor-BB (PDGF-BB) plays an important role in bone formation. However, little information is available about its effect on diabetic BMSCs. In this study, BMSCs were isolated from streptozotocin-induced diabetic rats. After treatment with recombinant human PDGF-BB (rhPDGF-BB), diabetic BMSCs demonstrated enhanced cell proliferation and osteogenic differentiation based on increased expressions of osteogenic genes (Runx2, alkaline phosphatase, and osteocalcin) and Runx2 protein, as well as upregulated alkaline phosphatase activity and mineralization. Furthermore, blocking extracellular signal regulated kinase (ERK) pathway by inhibitor PD98059 repressed the enhanced proliferation and osteogenic differentiation in diabetic BMSCs induced by rhPDGF-BB. Together, these results indicated that rhPDGF-BB stimulates proliferation and osteogenic differentiation partially through ERK pathway in diabetic BMSCs. Therefore, modulation of diabetic BMSCs could augment BMSCs function affected by diabetes and holds significance for future strategies to treat diabetic bone complications.
PMCID: PMC3925525  PMID: 24605332
22.  Controlled Delivery of Transforming Growth Factor β1 by Self-Assembling Peptide Hydrogels Induces Chondrogenesis of Bone Marrow Stromal Cells and Modulates Smad2/3 Signaling 
Tissue Engineering. Part A  2010;17(1-2):83-92.
Self-assembling peptide hydrogels were modified to deliver transforming growth factor β1 (TGF-β1) to encapsulated bone-marrow-derived stromal cells (BMSCs) for cartilage tissue engineering applications using two different approaches: (i) biotin-streptavidin tethering; (ii) adsorption to the peptide scaffold. Initial studies to determine the duration of TGF-β1 medium supplementation necessary to stimulate chondrogenesis showed that 4 days of transient soluble TGF-β1 to newborn bovine BMSCs resulted in 10-fold higher proteoglycan accumulation than TGF-β1-free culture after 3 weeks. Subsequently, BMSC-seeded peptide hydrogels with either tethered TGF-β1 (Teth-TGF) or adsorbed TGF-β1 (Ads-TGF) were cultured in the TGF-β1-free medium, and chondrogenesis was compared to that for BMSCs encapsulated in unmodified peptide hydrogels, both with and without soluble TGF-β1 medium supplementation. Ads-TGF peptide hydrogels stimulated chondrogenesis of BMSCs as demonstrated by cell proliferation and cartilage-like extracellular matrix accumulation, whereas Teth-TGF did not stimulate chondrogenesis. In parallel experiments, TGF-β1 adsorbed to agarose hydrogels stimulated comparable chondrogenesis. Full-length aggrecan was produced by BMSCs in response to Ads-TGF in both peptide and agarose hydrogels, whereas medium-delivered TGF-β1 stimulated catabolic aggrecan cleavage product formation in agarose but not peptide scaffolds. Smad2/3 was transiently phosphorylated in response to Ads-TGF but not Teth-TGF, whereas medium-delivered TGF-β1 produced sustained signaling, suggesting that dose and signal duration are potentially important for minimizing aggrecan cleavage product formation. Robustness of this technology for use in multiple species and ages was demonstrated by effective chondrogenic stimulation of adult equine BMSCs, an important translational model used before the initiation of human clinical studies.
PMCID: PMC3011906  PMID: 20672992
23.  Biologic Properties of Mesenchymal Stem Cells Derived From Bone Marrow and Adipose Tissue 
Journal of cellular biochemistry  2006;99(5):1285-1297.
The biologic characteristics of mesenchymal stem cells (MSCs) isolated from two distinct tissues, bone marrow and adipose tissue were evaluated in these studies. MSCs derived from human and non-human primate (rhesus monkey) tissue sources were compared. The data indicate that MSCs isolated from rhesus bone marrow (rBMSCs) and human adipose tissue (hASCs) had more similar biologic properties than MSCs of rhesus adipose tissue (rASCs) and human bone marrow MSCs (hBMSCs). Analyses of in vitro growth kinetics revealed shorter doubling time for rBMSCs and hASCs. rBMSCs and hASCs underwent significantly more population doublings than the other MSCs. MSCs from all sources showed a marked decrease in telomerase activity over extended culture; however, they maintained their mean telomere length. All of the MSCs expressed embryonic stem cell markers, Oct-4, Rex-1, and Sox-2 for at least 10 passages. Early populations of MSCs types showed similar multilineage differentiation capability. However, only the rBMSCs and hASCs retain greater differentiation efficiency at higher passages. Overall in vitro characterization of MSCs from these two species and tissue sources revealed a high level of common biologic properties. However, the results demonstrate clear biologic distinctions, as well.
PMCID: PMC4048742  PMID: 16795045
mesenchymal stem cells; bone marrow; adipose tissue; differentiation; telomerase; transcription factors
24.  Modulus-Driven Differentiation of Marrow Stromal Cells in 3D Scaffolds That Is Independent of Myosin-based Cytoskeletal Tension 
Biomaterials  2010;32(9):2256-2264.
Proliferation and differentiation of cells are known to be influenced by the physical properties of the extracellular environment. Previous studies examining biophysics underlying cell response to matrix stiffness utilized a two-dimensional (2D) culture format, which is not representative of the three-dimensional (3D) tissue environment in vivo. We report on the effect of 3D matrix modulus on human bone marrow stromal cell (hBMSC) differentiation. hBMSCs underwent osteogenic differentiation in poly(ethylene glycol) hydrogels of all modulus (300-fold modulus range, from 0.2 kPa to 59 kPa) in the absence of osteogenic differentiation supplements. This osteogenic differentiation was modulus-dependent and was enhanced in stiffer gels. Osteogenesis in these matrices required integrin-protein ligation since osteogenesis was inhibited by soluble Arginine-Glycine-Aspartate-Serine peptide, which blocks integrin receptors. Immunostained images revealed lack of well-defined actin filaments and microtubules in the encapsulated cells. Disruption of mechanosensing elements downstream of integrin-binding that have been identified from 2D culture such as actin filaments, myosin II contraction, and RhoA kinase did not abrogate hBMSC material-driven osteogenic differentiation in 3D. These data show that increased hydrogel modulus enhanced osteogenic differentiation of hBMSCs in 3D scaffolds but that hBMSCs did not use the same mechanosensing pathways that have been identified in 2D culture.
PMCID: PMC3381351  PMID: 21176956
three-dimensional culture; bone marrow stromal cell; cytoskeleton; hydrogels; matrix modulus
25.  Induction of unfolded protein response during neuronal induction of rat bone marrow stromal cells and mouse embryonic stem cells 
Experimental & Molecular Medicine  2009;41(6):440-452.
When we treated rat bone marrow stromal cells (rBMSCs) with neuronal differentiation induction media, typical unfolded protein response (UPR) was observed. BIP/GRP78 protein expression was time-dependently increased, and three branches of UPR were all activated. ATF6 increased the transcription of XBP1 which was successfully spliced by IRE1. PERK was phosphorylated and it was followed by eIF2α phosphorylation. Transcription of two downstream targets of eIF2α, ATF4 and CHOP/GADD153, were transiently up-regulated with the peak level at 24 h. Immunocytochemical study showed clear coexpression of BIP and ATF4 with NeuN and Map2, respectively. UPR was also observed during the neuronal differentiation of mouse embryonic stem (mES) cells. Finally, chemical endoplasmic reticulum (ER) stress inducers, thapsigargin, tunicamycin, and brefeldin A, dose-dependently increased both mRNA and protein expressions of NF-L, and, its expression was specific to BIP-positive rBMSCs. Our results showing the induction of UPR during neuronal differentiations of rBMSCs and mES cells as well as NF-L expression by ER stress inducers strongly suggest the potential role of UPR in neuronal differentiation.
PMCID: PMC2705864  PMID: 19322020
bone marrow; cell differentiation; embryonic stem cells; endoplasmic reticulum; neuron; stem cells; stress, physiological; stromal cells

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