Angiogenesis and Osteogenesis Mesenchymal Stem Cell Sheet with Activated Platelet-Rich Plasma Enhances Fracture Healing in a Rat Tibia Model

Purpose. Nonunion of fractured bones is a common clinical problem. In this report, we enhanced bone union by using angiogenic and osteogenic mesenchymal stem cell (MSC) sheets and activated platelet-rich plasma (PRP). Methods. The osteogenic differentiation of rat bone marrow-derived MSCs stimulated with activated PRP and MSC sheets stimulated with simvastatin and activated PRP were investigated in vitro. We further investigated osteogenesis in vivo in fractured rat tibias treated with MSC sheets, PRP, or MSC sheets and PRP. X-ray, micro-computed tomography, and histological analysis were performed at 2 and 8 weeks. Results. Alizarin red staining and quantification and alkaline phosphatase quantification showed the osteogenic potential of MSCs treated with activated PRP. The expression levels of alkaline phosphatase, osteocalcin, osteoprotegerin, and vascular endothelial growth factor in MSCs treated with simvastatin or in activated PRP-induced MSC sheets were significantly higher than those in non-induced MSC sheets, suggesting that angiogenesis and osteogenesis occurred. X-ray and micro-computed tomography photographs and histological sections showed callus formation around the fracture sites in the MSC sheet/PRP transplanted group. Bone union was achieved in the MSC sheet/PRP group at 8 weeks. Conclusions. Our results indicate that the fractures in our model were completely cured by transplanting MSC sheets with activated PRP. Angiogenic and osteogenic MSC sheets with locally applied activated PRP may have clinical use in the treatment of fractures, delayed bone union, or nonunion.