Human mesenchymal stem cells: Influence of oxygen pressure on proliferation and chondrogenic differentiation in fibrin glue in vitro.

Tissue engineering using biomaterials is a promising solution for cartilage replacement. The purpose of this study was to investigate whether the fibrin sealant Tissucol(R) provides a suitable scaffold for re-implanting stem cells during chondrogenic replacement therapy. Pluripotent stem cells were isolated from adult human bone marrow (hMSCs), cultured and characterized by FACS (CD105+/CD106+, CD45-/CD14-/CD34-). A large-holed porous hMSC-containing fibrin matrix was built that allowed hMSCs to survive throughout the period of culture (42 days) in either proliferation or chondrogenic differentiation medium under normoxic (21% O2) or hypoxic (3% O2) conditions. Morphology (as determined by electron microscopy) and proliferation (Ki67 staining) of the embedded hMSCs did not markedly vary under normoxic and hypoxic culture even after 42 days in culture. The stem cell marker Oct-4 was expressed during the whole culture period. Under chondrogenic differentiation conditions, especially under hypoxic conditions, we observed rounded chondrocyte-like cell types and a chondral phenotype assessed by mRNA expression of collagen II and Alcian blue staining. hMSCs seeded into large-holed porous preparations of Tissucol survive, proliferate and keep their stem cell character. Furthermore, culturing the cells in a corresponding medium induces chondrogenic differentiation, which could be remarkably and significantly enhanced under hypoxic conditions.