Umbilical cord stem cells released from alginate–fibrin microbeads inside macroporous and biofunctionalized calcium phosphate cement for bone regeneration

Abstract

The need for bone repair has increased as the population ages. The objectives of this study were to (1) develop a novel biofunctionalized and macroporous calcium phosphate cement (CPC) containing alginate–fibrin microbeads encapsulating human umbilical cord mesenchymal stem cells (hUCMSC) and, for the first time, (2) investigate hUCMSC proliferation and osteogenic differentiation inside the CPC. A macroporous CPC was developed using calcium phosphate powder, chitosan, and a gas-foaming porogen. Five types of CPC were fabricated: a CPC control, CPC+0.05% fibronectin (Fn), CPC+0.1% Fn, CPC+0.1% arginine–glycine–aspartate (RGD), and CPC+0.1% Fn+0.1% RGD. Alginate–fibrin microbeads containing 106hUCMSC per ml were encapsulated in the CPC paste. After the CPC had set, the degradable microbeads released hUCMSC within it. The hUCMSC proliferated inside the CPC, with the cell density after 21days being 4-fold that on day1. CPC+0.1% RGD had the highest cell density, which was 4-fold that of the CPC control. The released cells differentiated along the osteogenic lineage and synthesized bone mineral. The hUCMSC inside the CPC+0.1% RGD construct expressed the genes alkaline phosphatase, osteocalcin and collagen I, at twice the level of the CPC control. Mineral synthesis by hUCMSC inside the CPC+0.1% RGD construct was 2-fold that in the CPC control. RGD and Fn incorporation in the CPC did not compromise its strength, which matched the reported strength of cancellous bone. In conclusion, degradable microbeads released hUCMSC which proliferated, differentiated and synthesized minerals inside the macroporous CPC. The CPC with RGD greatly enhanced cell function. The novel biofunctionalized and macroporous CPC–microbead–hUCMSC construct is promising for bone tissue engineering applications.