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1.  Bone marrow osteoblast vulnerability to chemotherapy 
European journal of haematology  2013;90(6):469-478.
Osteoblasts are a major component of the bone marrow microenvironment which provide support for hematopoietic cell development. Functional disruption of any element of the bone marrow niche, including osteoblasts, can potentially impair hematopoiesis. We have studied the effect of two widely used drugs with different mechanisms of action, etoposide (VP16) and melphalan, on murine osteoblasts at distinct stages of maturation. VP16 and melphalan delayed maturation of preosteoblasts and altered CXCL12 protein levels, a key regulator of hematopoietic cell homing to the bone marrow. Sublethal concentrations of VP16 and melphalan also decreased the levels of several transcripts which contribute to the composition of the extracellular matrix (ECM) including osteopontin (OPN), osteocalcin (OCN) and collagen 1A1 (Col1a1). The impact of chemotherapy on message and protein levels for some targets was not always aligned, suggesting differential responses at the transcription and translation or protein stability levels. Since one of the main functions of a mature osteoblast is to synthesize ECM of a defined composition, disruption of the ratio of its components may be one mechanism by which chemotherapy affects the ability of osteoblasts to support hematopoietic recovery coincident with altered marrow architecture. Collectively, these observations suggest that the osteoblast compartment of the marrow hematopoietic niche is vulnerable to functional dysregulation by damage imposed by agents frequently used in clinical settings. Understanding the mechanistic underpinning of chemotherapy-induced changes on the hematopoietic support capacity of the marrow microenvironment may contribute to improved strategies to optimize patient recovery post-transplantation.
PMCID: PMC3662303  PMID: 23551534
bone marrow microenvironment; osteoblast; extracellular matrix; hematopoietic stem cell; chemotherapy
2.  Melphalan exposure induces an Interleukin-6 deficit in bone marrow stromal cells and osteoblasts 
Cytokine  2012;58(2):245-252.
Bone marrow stromal cells (BMSC) and osteoblasts are critical components of the microenvironment that support hematopoietic recovery following bone marrow transplantation. Aggressive chemotherapy not only affects tumor cells, but also influences additional structural and functional components of the microenvironment. Successful reconstitution of hematopoiesis following stem cell or bone marrow transplantation after aggressive chemotherapy is dependent upon components of the microenvironment maintaining their supportive function. This includes secretion of soluble factors and expression of cellular adhesion molecules that impact on development of hematopoietic cells. In the current study, we investigated the effects of chemotherapy treatment on BMSC and human osteoblast (HOB) expression of Interleukin-6 (IL-6) as one regulatory factor.
IL-6 is a pleiotrophic cytokine which has diverse effects on hematopoietic cell development. In the current study we demonstrate that exposure of BMSC or HOB to melphalan leads to decreases in IL-6 protein expression. Decreased IL-6 protein is the most pronounced following melphalan exposure compared to several other chemotherapeutic agents tested. We also observed that melphalan decreased IL-6 mRNA in both BMSC and HOB. Finally, using a model of BMSC or HOB co-cultured with myeloma cells exposed to melphalan, we observed that IL-6 protein was also decreased, consistent with treatment of adherent cells alone. Collectively, these observations are of dual significance. First, suggesting that chemotherapy induced IL-6 deficits in the bone marrow occur which may result in defective hematopoietic support of early progenitor cells. In contrast, the decrease in IL-6 protein may be a beneficial mechanism by which melphalan acts as a valuable therapeutic agent for treatment of multiple myeloma, where IL-6 present in the bone marrow acts as a proliferative factor and contributes to disease progression. Taken together, these data emphasize the responsiveness of the microenvironment to diverse stress that is important to consider in therapeutic settings.
PMCID: PMC3319530  PMID: 22356805
Interleukin-6; melphalan; bone marrow microenvironment; osteoblast; bone marrow stromal cell; chemotherapy
3.  Respiratory Syncytial Virus Infection in Human Bone Marrow Stromal Cells 
Respiratory syncytial virus (RSV) is the most common respiratory pathogen in infants and young children. The pathophysiology of this infection in the respiratory system has been studied extensively, but little is known about its consequences in other systems. We studied whether RSV infects human bone marrow stromal cells (BMSCs) in vitro and in vivo, and investigated whether and how this infection affects BMSC structure and hematopoietic support function. Primary human BMSCs were infected in vitro with recombinant RSV expressing green fluorescent protein. In addition, RNA from naive BMSCs was amplified by PCR, and the products were sequenced to confirm homology with the RSV genome. The BMSC cytoskeleton was visualized by immunostaining for actin. Finally, we analyzed infected BMSCs for the expression of multiple cytokines and chemokines, evaluated their hematopoietic support capacity, and measured their chemotactic activity for both lymphoid and myeloid cells. We found that BMSCs support RSV replication in vitro with efficiency that varies among cell lines derived from different donors; furthermore, RNA sequences homologous to the RSV genome were found in naive primary human BMSCs. RSV infection disrupted cytoskeletal actin microfilaments, altered cytokine/chemokine expression patterns, decreased the ability of BMSCs to support B cell maturation, and modulated local chemotaxis. Our data indicate that RSV infects human BMSCs in vitro, and this infection has important structural and functional consequences that might affect hematopoietic and immune functions. Furthermore, we have amplified viral RNA from naive primary BMSCs, suggesting that in vivo these cells provide RSV with an extrapulmonary target.
PMCID: PMC3175557  PMID: 20971883
asthma; bronchiolitis; chemotaxis; cytokines; hematopoiesis
4.  Bone Marrow Osteoblast Damage by Chemotherapeutic Agents 
PLoS ONE  2012;7(2):e30758.
Hematopoietic reconstitution, following bone marrow or stem cell transplantation, requires a microenvironment niche capable of supporting both immature progenitors and stem cells with the capacity to differentiate and expand. Osteoblasts comprise one important component of this niche. We determined that treatment of human primary osteoblasts (HOB) with melphalan or VP-16 resulted in increased phospho-Smad2, consistent with increased TGF-β1 activity. This increase was coincident with reduced HOB capacity to support immature B lineage cell chemotaxis and adherence. The supportive deficit was not limited to committed progenitor cells, as human embryonic stem cells (hESC) or human CD34+ bone marrow cells co-cultured with HOB pre-exposed to melphalan, VP-16 or rTGF-β1 had profiles distinct from the same populations co-cultured with untreated HOB. Functional support deficits were downstream of changes in HOB gene expression profiles following chemotherapy exposure. Melphalan and VP-16 induced damage of HOB suggests vulnerability of this critical niche to therapeutic agents frequently utilized in pre-transplant regimens and suggests that dose escalated chemotherapy may contribute to post-transplantation hematopoietic deficits by damaging structural components of this supportive niche.
PMCID: PMC3281873  PMID: 22363485

Results 1-4 (4)