Sustained BMP-2 release and platelet rich fibrin synergistically promote tendon-bone healing after anterior cruciate ligament reconstruction in rat

OBJECTIVE: Anterior cruciate ligament (ACL) injuries which cause knee disabilities remain a clinical challenge due to the compromised tendon-bone repair. Multiple strategies have been proposed to treat the tendon-bone injuries. and the combination of these therapies hold great potential to achieve synergistic effects. MATERIALS AND METHODS: We built PL-GA-BMP-2 (bone morphogenetic protein 2) system and confirmed the sustained release of BMP-2 both in vitro and in vivo. We then applied different therapies to treat rat ACL reconstruction. We collected the tissue sample and analyzed the BMP-2 concentration both in serum and in injured sites. We tested the mRNA expression of genes that were related to inflammation, tissue repair and bone formation in damaged tissues. We also analyzed the protein levels of some genes associated with tendon formation and check the function of newly generated bone through biomechanical test. RESULTS: We found that, compared to mono-therapies. simultaneous utilization of sustained BMP-2 release and platelet rich-fibrin (PRF) after anterior cruciate ligament reconstruction showed better therapeutic effects on tendon-bone healing in rat. This combined therapy efficiently enhanced the levels of growth factors that favor the angiogenesis and relieved the inflammatory responses in the injured sites. Of note, the combined therapy efficiently promoted the signals associated with bone formation and tendon regeneration. CONCLUSIONS: We demonstrated that the combined therapy with BMP-2 and PRF achieves synergistic effects on tendon-bone healing and holds great potential for the treatment of ACL reconstruction.