A significant clinical need exists for synthetic scaffold materials capable of supporting and promoting bone regeneration in vivo. Previous studies from our laboratory have established that mesenchymal stem cells (MSCs) can be cultured on porous scaffolds under engineered conditions in vitro to generate a mineralized bioactive extracellular matrix coating of the scaffolds, which induces the osteogenic differentiation of subsequently cultured MSCs in vitro. The overall objectives of this study were to explore the application of biodegradable poly(ε-caprolactone) (PCL) scaffolds in generating mineralized bioactive extracellular matrix constructs and to assess the effect of the osteogenic culture medium supplement dexamethasone on the osteogenic differentiation of MSCs cultured on these constructs in vitro.

MSCs were harvested from the femora and tibiae of rats, expanded in osteogenic medium supplemented with dexamethasone for 6 days, seeded onto electrospun PCL fiber mesh scaffolds, and then cultured statically for 12 days in osteogenic medium supplemented with dexamethasone to produce mineralized bone-like extracellular matrix constructs. These constructs were then decellularized, seeded with freshly harvested and expanded MSCs, and cultured statically for 4, 8 and 16 days in osteogenic medium either with or without dexamethasone supplementation. MSCs were cultured in parallel on plain PCL scaffolds. Additionally, acellular PCL/ECM constructs were cultured in osteogenic medium supplemented with dexamethasone as a control. Following culture, the cellularity, alkaline phosphatase activity, and calcium content of scaffolds from each group were assessed.

This study demonstrates that MSCs cultured on PCL scaffolds in the presence of dexamethasone produce mineralized extracellular matrix constructs that direct the osteogenic differentiation of and mineral deposition by MSCs. Additionally, the PCL/ECM constructs support the osteogenic differentiation of MSCs (previously expanded in medium supplemented with dexamethasone), even in the absence of dexamethasone from the secondary culture medium. Finally, acellular PCL/ECM constructs alone induce mineral deposition from the culture medium. These novel bioactive mineralized constructs present tremendous potential for application as cell transplantation vehicles or as acellular scaffolds for bone tissue regeneration.