Biodegradable ECM-coated PCL microcarriers support scalable human early MSC expansion and in vivo bone formation

We found that heMSCs proliferate well on PCL MCs coated with a fibronectin, poly-l-lysine, and fibronectin (FN+PLL+FN) coating (cPCL MCs). During in vitro osteogenic induction, heMSCs cultured on cPCL MCs displayed a 68% increase in specific calcium deposition compared with cultures on MNL. In a mouse ectopic mineralization model, bone mass was equivalent for MNL-expanded and cPCL MC-bound heMSC implants but higher in both cases when compared with cell-free cPCL MC implants at 16 weeks post-implantation. In summary, compared with MNL cultures, biodegradable MC MSC cultures provide the benefits of large-scale expansion of cells and can be delivered in vivo, thereby eliminating the need for cell harvesting and use of scaffolds for cell delivery. These results highlight the promise of delivering heMSCs cultured on cPCL MCs for bone applications.