Label-free quantitative proteomics analysis models in vivo and in vitro reveal key proteins and potential roles in sciatic nerve injury

Background: The underlying mechanism of sciatic nerve injury (SNI) is a common motor functional disorder, necessitates further research. Methods: A rat model of SNI was established, with the injury group subjected to compressive injury of the right sciatic nerve exposed at the midpoint of the thigh and the sham surgery group undergoing the same surgical procedure. An oxygen-glucose deprivation model was employed to simulate in vitro SNI in PC12 cells. Following data acquisition and quality control, differentially expressed proteins (DEPs) in each model were identified through differential analysis, and enrichment analysis was used to explore the potential functions and pathways of the DEPs. Venn diagrams were drawn, and DEPs from both in vivo and in vitro SNI models were imported into the STRING database to construct a protein-protein interaction network and screen for hub proteins. Results: After the peptide segments obtained from rat nerve blockade and PC12 cells met quality requirements, 258 DEPs were identified in rat nerve samples, and 119 DEPs were screened in PC12 cells. Enrichment analysis revealed that DEPs in the rat model were predominantly concentrated in biological functions such as myogenic cell proliferation and signaling related to lipid and energy metabolism. DEPs in the in vitro model were mainly enriched in biological processes such as phagocytosis and were associated with lipid transport and metabolism. Two hub proteins, amyloid precursor protein (APP) and fibronectin 1 (FN1), were identified through MCC, MCODE, and Degree scoring. Both PC12 cells and external validation sets showed relatively higher expression of APP and FN1 in injured samples. Results of gene set enrichment analysis indicated that these two proteins were associated with metabolic pathways, such as biosynthesis of glycosaminoglycan chondroitin sulfate and biosynthesis of unsaturated fatty acids. Conclusion: APP and FN1 are potential key molecules involved in SNI and are associated with various metabolic pathways in nerve repair. These findings provide a theoretical basis for the development of therapeutic targets for SNI.