Osteoblastic differentiation of human and equine adult bone marrow-derived mesenchymal stem cells when BMP-2 or BMP-7 homodimer genetic modification is compared to BMP-2/7 heterodimer genetic modification in the presence and absence of dexamethasone.

Bone marrow-derived mesenchymal stem cells (BMDMSCs) have been targeted for use in enhancement of bone healing; and their osteogenic potential may be further augmented by genes encoding bone morphogenetic proteins (BMP's). The purpose of this study was to compare the effect of genetic modification of human and equine BMDMSCs with BMP-2 or -7 or BMP-2 and -7 on their osteoblastogenic differentiation in the presence or absence of dexamethasone. The BMDMSCs were harvested from the iliac crest of three human donors and tuber coxae of three equine donors. Monolayer cells were genetically modified using adenovirus vectors encoding BMP-2, -7 or both and cultured in the presence or absence of dexamethasone. Expression of BMPs was confirmed by enzyme linked immunosorbent assay (ELISA). To evaluate osteoblastic differentiation, cellular morphology was assessed every other day and expression and secretion of alkaline phosphatase (ALP), as well as expression levels of osteonectin (OSTN), osteocalcin (OCN), and runt-related transcription factor-2 (Runx2) were measured for up to 14 days. Human and equine BMDMSCs showed a capacity for osteogenic differentiation regardless of genetic modification or dexamethasone supplementation. Dexamethasone supplementation was more important for osteoblastogenic differentiation of equine BMDMSCs than human BMDMSCs. Genetic modification of BMDMSCs increased ALP secretion with AdBMP-2 homodimer having the greatest effect in both human and equine cells compared to AdBMP 7 or AdBMP 2/7. BMP protein elution rates reached their maximal concentration between day 4 and 8 and remained relatively stable thereafter, suggesting that genetically modified BMDMSCs could be useful for cell-based delivery of BMPs to a site of bone formation.