Regeneration of the Osteochondral Defect by a Wollastonite and Macroporous Fibrin Biphasic Scaffold

Osteochondral defect refers to the damage of cartilage as well as subchondral bone. Cartilage tissue engineering focusing on the regeneration of cartilage and disregarding the subchondral bone always leads to partial regeneration of the damage, resulting in poor mechanical and physiological properties. A scaffold suitable for in situ inductive regeneration of both types of tissues is urgently needed. In this study, a biphasic scaffold integrated by macro-porous fibrin and 3D-printed wollastonite (containing 8% MgSiO3 (CS-Mg8)) scaffolds, either preloaded with rabbit bone marrow mesenchymal stem cells (BMSCs) or not, were fabricated and used to repair osteochondral defects in vivo (full thickness osteochondral defects in rabbits, 4 mm in diameter and 4 mm in depth with bone marrow blood effusion). The fibrin scaffold had a pore size of 100-200 ym, and was degraded gradually and reached weight loss over 80% at 28 days. The presence of BMSCs could accelerate the degradation rate. BMSCs could well proliferate in the fibrin scaffold along with time prolongation. The CS-Mg8 scaffold possessed a regular structure of cross stacked CS-Mg8 rods, and was degraded rather slowly with a mass loss of 8.5% at 28 days. BMSCs adhered and showed well spreading on the CS-Mg8 scaffold, without apparent proliferation in vitro. In vivo transplantation of the biphasic scaffolds, either preloaded with BMSCs or not, could induce the regeneration of both cartilage and subchondral bone to a great extent. Loading of BMSCs enabled better regeneration of cartilage layer, leading to smoother macroscopic appearance, good integrity with surrounding tissue and tide mark formation. However, no significant difference in bone formation and in gene expression was found with and without BMSCs loading.