Silk-Poly(lactic-co-glycolic acid) Scaffold/Mesenchymal Stem Cell Composites for Anterior Cruciate Ligament Reconstruction in Rabbits

Natural silk fibroin scaffold has excellent mechanical properties, but degrades slowly. We constructed silk fibroin scaffolds for use in anterior cruciate ligament (ACL) reconstruction and incorporated poly(lactic-co-glycolic acid) (PLGA; 10: 90) within the structures to adjust the overall degradation rate. Silk fibroin-PLGA fibers (mixed at a mass ratio of 48: 52) were twisted into rope and weft-knitted into mesh. Then rabbit autologous bone marrow mesenchymal stem cells (BMSCs)-seeded rope was encapsulated with BMSCs-seeded mesh to establish rope-mesh binding scaffold-BMSC composites. Thereafter, the scaffold-BMSC composite was implanted into rabbit ACL defects. By 26 weeks after implantation, a direct insertion site-like structure had formed at the ligament-bone junction. Moreover, neo-ACL tissue expressed type I collagen, type III collagen, and tenascin-C mRNA, indicating the formation of ligament-like tissues. However, the silk fibroin fibers did not degrade completely. The maximum tensile load on the new ligament-bone interface was 101.2 +/- 13.4 N in the scaffold- BMSC group, significantly higher than that tolerated by the simple scaffold without BMSCs. Our findings suggest that silk fibroin-PLGA-BMSC composites can adequately reconstruct the anterior cruciate ligament in rabbits.