Enhanced osteogenic gene expression in microcarrier-bound scalably expanded fetal bone marrow MSCS

Abstract

Mesenchymal stem cell (MSC) therapy is a promising strategy to address the unmet clinical need for improved bone regeneration. However, challenges to the scalable stem cell production hinder the clinical translation of MSC therapy. Furthermore, the effects of scalable microcarrier-based culture and enzymatic cell harvest on the phenotype and molecular identity of MSCs upon directed osteogenic differentiation are not well understood. In order to address these issues, we expanded fetal bone marrow MSCs on either commercially-available microcarriers in spinner flask culture or on control tissue culture plastic (TCP) monolayer surfaces. At the end of this expansion, we characterized the phenotype of microcarrier- or TCP monolayer-expanded MSCs in terms of cytokine, gene and surface marker expression. We then differentiated microcarrier-bound, microcarrier-harvested or plastic-harvested MSCs which were seeded onto collagen-coated plates or polycaprolactone-tricalcium phosphate scaffolds. In both cases, microcarrier-bound MSCs displayed increased expression of osteogenic genes such as RUNX2 and ALPL compared to microcarrier-harvested and plastic-harvested cells upon osteogenic induction. These results indicate that microcarrier-bound MSCs undergo enhanced osteogenic differentiation. Our findings also suggest that compared to conventional methods of delivering MSC cell suspensions that were harvested either from microcarriers cultured in agitated bioreactors or from TCP surfaces, in vivo delivery of MSC-bound microcarriers may present a promising method for bone regeneration.