Overexpression of Hif-1α in Mesenchymal Stem Cells Affects Cell-Autonomous Angiogenic and Osteogenic Parameters.

Reconstruction of large bone defects still represents a major medical challenge. In recent years tissue engineering has developed techniques based on adult mesenchymal stem cells (MSCs) that could represent an attractive therapeutical option to treat large bone defects in the future. It has been demonstrated in various animal models that ex vivo expanded MSCs are capable of promoting the regeneration of skeletal defects after implantation. However, for the efficient regeneration of bone in tissue engineering applications, a rapid vascularization of implanted grafts is essential to ensure the survival of cells in the early post-implantational phase. A promising strategy to enhance vascularization of MSC-containing implants could consist of overexpression of the angiogenic master transcription factor Hypoxia-inducible factor 1 (Hif-1) in the MSCs in order to induce angiogenesis and support osteogenesis. In the present study, we overexpressed Hif-1α in MSCs by using recombinant adenoviruses and investigated cell-autonomous effects. Overexpression of Hif-1α enhanced proliferation, migration, cell survival and expression of pro-angiogenic genes. Other parameters such as expression of the osteogenic markers BMP-2 and RunX2 were decreased. Hif-1α overexpression had no effect on invasion, senescence and osteogenic differentiation of MSCs. Our experiments revealed multifarious effects of Hif-1α overexpression on cell-autonomous parameters. Therefore, Hif-1α overexpression may represent a therapeutic option to improve cellular functions of MSCs to treat critical sized bone defects.