The Effect of Tension on Gene Expression in Primary Nerve Repair via the Epineural Suture Technique

Introduction: The precise mechanism through which excessive tension confers poor outcomes in nerve gap repair is yet to be elucidated. Furthermore, the effect of tension on gene expression in regenerating nerves has not been characterized. This study investigated differential gene expression in transected nerves repaired under high and minimal tension. Methods: Male Lewis rats underwent right sciatic nerve transection with either minimaltension or high-tension repair. Fourteen weeks postoperatively, segments of the right sciatic nerves were harvested along with equal-length segments from the contralateral, healthy nerve to serve as internal controls (naive nerve). Differentially expressed genes (DEGs) and differentially regulated biochemical pathways between the samples were identified. Results: Seventeen animals were studied. The gene expression profiles of naive nerve and minimal-tension repair demonstrated minimal within-group variation, whereas that of high-tension repair demonstrated heterogeneity. Relative to naive nerve, high-tension repair samples had 4276 DEGs (1941 upregulated and 2335 downregulated) and minimaltension repair samples had 3305 DEGs (1479 upregulated and 1826 downregulated). Hightension repair samples had 360 DEGs relative to minimal-tension repair samples (68 upregulated and 292 downregulated). Upregulated biological pathways in all repaired nerves included steroid biosynthesis, extracellular matrix-receptor interaction, and ferroptosis. Finally, upregulated pathways in high-tension repair samples relative to minimaltension repair samples included tumor necrosis factor signaling, interleukin-17 signaling, cytokine-cytokine receptor interaction, and mitogen-activated protein kinase signaling. Conclusions: The improved outcomes achieved with minimal-tension nerve repair may take root in a favorable gene expression profile. Future elucidation of biochemical pathways in nerve regeneration may identify potential therapeutic targets to optimize primary nerve repair outcomes.