Tissue culture of human alveolar periosteal sheets using a stem-cell culture medium (MesenPRO-RS™): In vitro expansion of CD146-positive cells and concomitant upregulation of osteogenic potential in vivo.

We have previously demonstrated that multilayered periosteal sheets prepared from the explant culture of alveolar periosteum serve as a promising osteogenic grafting material in periodontal tissue regeneration. For the preparation of more potent periosteal sheets, we examined the applicability of stem-cell culture media. Compared to the control medium (Medium 199+10% FBS), periosteal sheets expanded with MesenPRO-RS™ medium exhibited these features: Cells grew three-dimensionally and deposited collagen in the extracellular spaces to form thicker multilayers of cells. Chondrocytic markers were not significantly upregulated. Contractile force was generated in proportion with the increased thickness of the periosteal sheets and the formation of cytoplasmic α-smooth muscle actin fibers. However, myofibroblastic markers were not significantly upregulated. The surface marker CD146 was substantially upregulated, while both CD73 and CD105 were downregulated. Alkaline phosphatase, a representative osteoblastic marker, was not upregulated by osteogenic induction. However, these expanded periosteal sheets exhibited substantially stronger osteogenic differentiation when implanted in nude mice. Therefore, despite our reservations, MesenPRO medium effectively expanded the cells contained in periosteal sheets to promote the formation of thicker multilayers of cells in vitro, and these enhanced periosteal sheets expressed increased osteogenic potential at implantation sites in vivo. In conjunction with data indicating that CD146-positive cells were notably expanded and the recently proposed concept that CD146 is a marker for osteogenic progenitor cells found in the bone marrow stroma, our findings suggest that MesenPRO medium improves the preparation of highly osteogenic periosteal sheets suitable for clinical application largely through the induction of CD146-positive cells.