Ligament-to-bone interface tissue regeneration using a functionalized biphasic silk fibroin scaffold

Abstract

The emergence of the tissue engineering approach has shown to be a game changer in ligament reconstruction, making it possible to create multi-phasic scaffold structures for multi-specific tissue regeneration. To regenerate the bone-ligament-bone tissue, mimicking hard to soft tissue transition, we propose the use of a functionalized biphasic silk scaffold. Hydroxyapatite nanoparticles (nHA) and bone morphogenetic protein 2 (BMP2) were loaded in the ends of Bombyx mori silk fibroin (SF) scaffold system to enhance enthesis regeneration and bone tunnel healing, while the central onethird supported ligament regeneration. Two groups of biphasic scaffolds, distinguished by the different ends’ additive, were fabricated: nHA only (Ctrl) and n-HA/BMP2 (Exp). A series of bench work, small animal study and large animal preclinical trial was performed using MSC-seeded constructs for the reconstruction of excised ACL. The bioactivity of BMP2 was ascertained and shown to be eluting with an initial burst, followed by a lowered sustained release. Osteogenic genes were upregulated in both groups compared to pure SF. By 24 weeks in vivo, the ACL was regenerated and bone tunnel narrowing was observed with histological evidences indicating new bone and enthesis regeneration in Exp. Better graft to bone integration was observed in Exp compared to Ctrl. From this study, it was demonstrated that the BMP2 eluting biphasic silk scaffold is promising as an advanced tissue engineering treatment modality for complete bone-ligament-bone reconstruction.