ObjectiveTo investigate the effectiveness of autologous injectable platelet rich fibrin (i-PRF) combined with bone marrow mesenchymal stem cells (BMSCs) for sciatic nerve injury in rats.MethodsBMSCs were isolated and cultured from tibial bone marrow of Sprague Dawley (SD) neonatal rats aged 10-15 days and passaged to the 4th generation. i-PRF was prepared from posterior orbital venous blood of adult SD rats by improved low-speed centrifugation. Twenty-four adult SD rats were selected and randomly divided into 4 groups with 6 rats in each group after the sciatic nerve Ⅲ degree injury model was established by modified crush injury method. Groups A, B, C, and D were injected with BMSCs suspension+autologous i-PRF, autologous i-PRF, BMSCs suspension, and normal saline, respectively. The Basso-Beattie-Bresnahan (BBB) score was used to evaluate the recovery of neurological function of the affected limb of rats every week from 1 to 8 weeks after operation. At 2 months after operation, the rats were sacrificed and the histological changes of sciatic nerve were observed by HE staining. The microstructural changes of nerve fibers, myelin sheath, and nucleus were observed by transmission electron microscope. The expressions of N-cadherin, Nestin, and glial fibrillary acidic protein (GFAP) were detected by Western blot.ResultsNo immune rejection or death occurred in the rats after operation. There was no significant difference in BBB scores between groups at 1 week after operation (P>0.05); at 2-8 weeks after operation, BBB scores in group A were significantly higher than those in groups B, C, and D, and in groups B, C than in group D (P<0.05), there was no significant difference between groups B and C (P>0.05). HE staining showed that the nerve fibers in group A arranged in order, without defect or demyelination; the nerve fibers in group B were not clear and slightly swollen; some of the nerve fibers in group C were disordered and demyelinated; the nerve fibers in group D were not continuous, obviously demyelinated, and some of the nerve adventitia damaged. Transmission electron microscope showed that the structure of nerve fibers in group A was clear, myelin sheath was complete, and nucleus was dense; group B was slightly less than group A; group C had fuzzy structure, demyelination, and hollowing out; group D had disorder structure, demyelination, and hollowing out, and the middle part of nerve adventitia continuity. Western blot detection results showed that there was no significant difference in the relative expression of Nestin between groups (P>0.05). The relative expression of N-cadherin was significantly lower in groups B, C, and D than in group A, in groups C and D than in group B, and in group D than in group C (P<0.05). The relative expression of GFAP was significantly lower in groups B, C, and D than in group A, in group D than in groups B and C (P<0.05); there was no significant difference between groups B and C (P>0.05).ConclusionAutologous i-PRF combined with BMSCs can effectively treat sciatic nerve tissue injury in rats.