Bone marrow-derived mesenchymal stem cells express the pericyte marker 3G5 in culture and show enhanced chondrogenesis in hypoxic conditions.

ABSTRACT

Bone marrow-derived mesenchymal stem cells are a potential source of cells for the repair of articular cartilage defects. Hypoxia has been shown to improve chondrogenesis in some cells. In this study, bone marrow-derived stem cells were characterized and the effects of hypoxia on chondrogenesis investigated. Adherent bone marrow colony-forming cells were characterized for stem cell surface epitopes, and then cultured as cell aggregates in chondrogenic medium under normoxic (20% oxygen) or hypoxic (5% oxygen) conditions. The cells stained strongly for markers of adult mesenchymal stem cells, and a high number of cells were also positive for the pericyte marker 3G5. The cells showed a chondrogenic response in cell aggregate cultures and, in lowered oxygen, there was increased matrix accumulation of proteoglycan, but less cell proliferation. In hypoxia, there was increased expression of key transcription factor SOX6, and of collagens II and XI, and aggrecan. Pericytes are a candidate stem cell in many tissue, and our results show that bone marrow-derived mesenchymal stem cells express the pericyte marker 3G5. The response to chondrogenic culture in these cells was enhanced by lowered oxygen tension. This has important implications for tissue engineering applications of bone marrow-derived stem cells.