Fresh Platelet-Rich Plasma Gel Reduces Sciatic Nerve-Associated Neuropathic Pain in Rats by Suppressing Tumor Necrosis Factor-α and Interleukin-6 Expression

Objective: Nerve wrapping using biomaterials has shown promising results in promoting nerve regeneration and improving functional outcomes in revision surgery cases. Our previous study on the local administration of basic fibroblast growth factor via a carrier demonstrated a limited effect. Thus, we have focused on platelet-rich plasma (PRP), a treatment material with recent evidence of tissue repair effects, and on a method of wrapping injured nerves by gelatinizing PRP without a carrier. However, there are few reports on studies targeting peripheral neuropathic pain. This study aimed to examine the efficacy and mechanism of action of this method. Materials and methods: Wistar rats were employed as a model of chronic constriction injury (CCI) and divided into two groups: CCI (untreated) and PRP-G (treated with PRP gel wrapping). PRP gels were prepared by centrifuging peripheral blood from other rats, followed by activation. Pain behavior test and real-time quantitative polymerase chain reaction of sciatic nerve RNA were conducted on postoperative days (PODs) three, seven, and 14 to quantify tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) (Tnf-α and Il-6) gene expression. Results: Pathological evaluations of sciatic nerves performed on POD seven to investigate the neuroprotective effects of PRP gel wrapping revealed a significantly higher density of myelinated axons in the PRP-G group. In the CCI group after POD three, the pain threshold decreased to 0.88 ± 0.22 g, which was approximately one-third of the pre-treatment level, while the PRP-G group showed a pain threshold approximately twice that of the CCI group. Quantitative PCR results showed that, compared to untreated rats, both groups exhibited significantly increased expression of Tnf-α and Il-6 in the sciatic nerve after POD three. However, at POD seven and POD 14, the increase in expression was significantly reduced to approximately half that of the CCI group in the PRP-G group. Conclusions: PRP gel wrapping has a substantial long-term suppression effect on neuropathic pain, possibly involving suppression of Tnf-α and Il-6 expression in the nerves. This study suggests that PRP gel wrapping may be clinically applicable as an adjunctive therapy for peripheral nerve injury.