ABSTRACT
BACKGROUND:Platelet-rich plasma has been shown to enhance the viability and the pro-angiogenesis capacity of mesenchymal stem cells.Extracellular vesicles are one of the key mediators for mesenchymal stem cells to exert their effects,but currently,it is unclear whether platelet-rich plasma affects the functions of extracellular vesicles. OBJECTIVE:To investigate the effects of platelet-rich plasma on the function of extracellular vesicles from bone marrow mesenchymal stem cells,verify whether platelet-rich plasma can be used as an adjuvant to enhance the healing effects of bone marrow mesenchymal stem cells on repairing the peripheral nerve injury. METHODS:For in vitro study,bone marrow mesenchymal stem cells were cultured under normal conditions and with 1%platelet-rich plasma.The ultracentrifugation was used to extract the extracellular vesicles produced by bone marrow mesenchymal stem cells cultured under normal conditions(EVs-nor)or the condition supplemented with 1%platelet-rich plasma(EVs-prp).Extracellular vesicles were used to incubate with Schwann cells.The EdU assay,western blot assay,qPCR and light microscopy photography were performed to examine the effects of EVs-nor and EVs-prp on Schwann cell reprogramming,which was characterized by cell proliferation,c-Jun expression,reprogramming-associated gene expression and cell morphology.For in vivo study,the model of sciatic nerve injury in rats was established.Bone marrow mesenchymal stem cells were grafted with or without 1%platelet-rich plasma into the injured rat sciatic nerve using a chitin nerve conduit.Eight weeks after the surgery,the recovery was assessed by histological and functional indexes,including regenerated nerve fiber density,gastrocnemius wet weight ratio and sciatic function index. RESULTS AND CONCLUSION:(1)Compared with EVs-nor,EVs-prp was stronger in promoting Schwann cell proliferation.The gene expressions of c-Jun and GDNF were significantly upregulated in EVs-prp treated Schwann cells.The morphology of Schwann cells was significantly longer in EVs-prp group than that in EVs-nor group,indicating that EVs-prp had a stronger ability to stimulate Schwann cell reprogramming than EVs-nor.(2)Sciatic nerve injury animal experiment results revealed that grafting mesenchymal stem cells along with platelet-rich plasma into the injured sciatic nerve showed the best recovery compared with grafting mesenchymal stem cells or platelet-rich plasma alone,demonstrated by the significantly improved density of nerve fibers,gastrocnemius wet weight ratio,and sciatic function index.(3)These results suggested that platelet-rich plasma improved the function of bone marrow mesenchymal stem cell-derived extracellular vesicles and could be served as a practical and feasible preparation to synergize with bone marrow mesenchymal stem cells to improve peripheral nerve repair.