In vitro and in vivo investigation of PLA/PCL scaffold coated with metformin-loaded gelatin nanocarriers in regeneration of critical-sized bone defects

BackhroundsLarge bone defects constitute a major challenge in bone tissue engineering andusually fail to heal due to the incomplete differentiation of recruited mesenchymalstem cells (MSCs) into osteogenic precursor cells. As previously proposed, metformin(MET) induces differentiation of MSCs into osteoblastic lineages in vitro, however thepotential effects of this drug on the regeneration of critical sized-defects were not established yet. The current study is aimed to fabricate a novel scaffold to examine theeffect of metformin on bone regeneration via a controlled local delivery system.MethodsWe fabricated a Poly (lactic acid) and Polycaprolactone (PLA/PCL) scaffold to deliverMET-loaded gelatin nanocarriers (MET/GNs) to critical size calvarial bone defects ina rat model. The fabricated scaffolds were characterized by biomechanical analysis,scanning electron microscopy, porosity, contact angle, degradation rate, and bloodcompatibility test. Moreover, the effect of fabricated scaffolds on cell viability andtheir osteogenic diffentiation was evaluated under in vitro condition. In animal study,the defects were randomly filled with autograft, scaffolds and a group was left emptywithout any treatment.ResultsqRT-PCR analyses showed the expression level of osteogenic and angiogenic markersconsiderably increased in MET/GNs-PLA/PCL. The in vivo results showed that sustainedrelease of metformin improved bone ingrowth, angiogenesis and defect reconstructionat 8 weeks post-implantation as evaluated by histological, immunohistochemical, CTscan and biomechanical analysis.ConclusionsThese data strongly indicate that local delivery of metformin can help improve thebone healing process. The results of the present study provide the first-time in vivoevidence regarding induction of osteogenic differentiation of MSCs by sustained localdelivery of metformin.