Mineralized collagen scaffolds induce hMSC osteogenesis and matrix remodeling

Biomaterials for bone tissue engineering must be able to instruct cell behavior in the presence of the complex biophysical and biomolecular environments encountered in vivo. While soluble supplementation strategies have been identified to enhance osteogenesis, they are subject to significant diffusive loss in vivo or the need for frequent re-addition in vitro. This investigation therefore explored whether biophysical and biochemical properties of a mineralized collagen-GAG scaffold were sufficient to enhance human mesenchymal stem cell (hMSC) osteogenic differentiation and matrix remodeling in the absence of supplementation. We examined hMSC metabolic health, osteogenic and matrix gene expression profiles, as well as matrix remodeling and mineral formation as a function of scaffold mineral content. We found that scaffold mineral content enhanced long term hMSC metabolic activity relative to non-mineralized scaffolds. While osteogenic supplementation or exogenous BMP-2 could enhance some markers of hMSC osteogenesis in the mineralized scaffold, we found the mineralized scaffold was itself sufficient to induce osteogenic gene expression, matrix remodeling, and mineral formation. Given significant potential for unintended consequences with the use of mixed media formulations and potential for diffusive loss in vivo, these findings will inform the design of instructive biomaterials for regenerative repair of critical-sized bone defects, as well as for applications where non-uniform responses are required, such as in biomaterials to address spatially-graded interfaces between orthopedic tissues.