Accelerated Spinal Fusion By Collagen Scaffolds Modified With Low Dosage Of Engineered Collagen-binding Human Bone Morphogenetic Protein-2in Rats

Background: Bone morphogenetic protein-2(BMP-2) is a potent osteoinductivecytokine that plays a critical role in bone regeneration and repair. However, itsdistribution and side effects are major barriers to its success as therapeutic treatment.The improvement of therapy using collagen delivery matrices has been reported. Toinvestigate the effects of BMP-2at a low dosage on spinal fusion, both engineeredhuman BMP-2with a collagen binding domain (CBD-BMP-2) and collagen scaffoldswere developed and their combination was implanted into Sprague-Dawley (SD) rats tostudy Lumbar4-5(L4-L5) posterolateral spine fusion.Method:(1) In vitro, CBD-BMP-2and BMP-2were used to induce MC-3T3-E1to differentiate into osteoblasts. ALP kit was applied to detect alkaline phosphatase(ALP)content in lysis solution. Then, we linked both them to the collagen scaffolds and got abinding rate and release curve.(2) In vivo, We divided SD rats into three groups, thesham group (G1), the collagen scaffold-treated group (G2) and the BMP-2-loadedcollagen scaffolds group (G3).8weeks or16weeks after surgery, the spines of the ratswere evaluated by X-radiographs, high-resolution micro-computed tomography(micro-CT), manual palpation and hematoxylin and eosin (H&E) staining.Result:(1) in vitro, we contrast the CBD-BMP-2to commercial BMP-2and foundthey have the same osteogenic ability. Compared to the BMP-2group, a higher bindingrate and a flat release curve are detected in CBD-BMP-2group in vitro.(2) in vivo, Theresults showed that spine L4-L5fusions occurred in G2and G3group, while resultsfrom the sham group were inconsistent. Moreover, G3had better results than G2,including higher fusion efficiency, higher bone mineral density (BMD) and more bonetrabecular formation. Conclusion: The results demonstrated that with site-specific collagen bindingdomain, low dose of BMP-2loaded on collagen scaffolds enhanced the posterolateralintertransverse process fusion in rats. It suggested that combination delivery could be analternative in spine fusion with dramatically decreased side effects caused by high doseof BMP-2.