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

Large bone defects constitute a major challenge in bone tissue engineering and usually fail to heal due to the incomplete differentiation of recruited mesenchymal stem cells (MSCs) into osteogenic precursor cells. As previously proposed, metformin (MET) induces differentiation of MSCs into osteoblastic lineages in vitro. We fabricated a Poly (lactic acid) and Polycaprolactone (PLA/PCL) scaffold to deliver metformin loaded gelatin nanocarriers (MET/GNs) to critical-sized calvarial bone defects in a rat model. The scaffolds were evaluated regarding their morphology, porosity, contact angle, degradation rate, blood compatibility, biomechanical, cell viability and their osteogenic differentiation. In animal study, the defects were filled with autograft, scaffolds and a group was left empty. qRT-PCR analyses showed the expression level of osteogenic and angiogenic markers considerably increased in MET/GNs-PLA/PCL. The in vivo results showed that MET/GNs-PLA/PCL improved bone ingrowth, angiogenesis and defect reconstruction. Our results represent the applicability of MET/GNs-PLA/PCL for successful bone regeneration. The effects of local delivery of metformin (MET) in osteogenic differentiation and healing of the critical sized-calvarial bone defect was evaluated in vitro and in vivo. MET loaded gelatin nanocarriers (MET/GNs) were papered, using the nanoprecipitation method. The poly caprolactone-poly (L-lactic) acid hybrid scaffold (PCL/PLA) was then coated by MET/GNs and characterized by different methodologies. The fabricated scaffolds were implanted into the critical sized-calvarial bone defects and resulted in significant enhanced new bone formation and bone healing in comparison to those of the control ones. Our results suggest that MET increased the expression level of the osteogenic and angiogenic genes; these were confirmed by in vivo results via the local sustained delivery of MET. [Display omitted]