Muscle atrophy and fibrosis are attenuated after experimental nerve repair associated with heterologous fibrin biopolymer.

BACKGROUND: Neurotmesis leads to neuromuscular junction (NMJ) degeneration, muscle atrophy, and functional loss. While neurorrhaphy is standard, motor recovery is often incomplete. Heterologous fibrin biopolymer (HFB) shows potential as an adjunct, hence, we investigate HFB's late regenerative effects. MATERIAL/METHODS: Twenty adult male Wistar rats (CEUA-FMB 1402/2021) were divided into Control (C), Denervated (D), Neurorrhaphy (N), and Neurorrhaphy + HFB (NB) groups. After 120 days, nerves and muscles were analyzed. RESULTS: NB (1355 ± 170.4) showed more intact axons than C (927 ± 170.4, p = .0026) and N (774 ± 158.2, p = .0002). NMJ morphology in NB was closer to C than N, with increased nAChR alpha-1 (NB vs. N p = .0428; NB vs C p = .0084) and Rapsyn (NB vs. N p = .0130; NB vs C p = .0053) expression. Muscle integrity in NB resembled C, exhibiting less atrophy (area: C vs. N p = .0002; NB vs. N p = .0117; perimeter: C vs. N p = .0002; NB vs. N p = .0114; central nuclei: C vs. N p = .0009; NB vs. N p = .0110) and fibrosis (C vs. N p = .0061; N vs. NB p = .0326) compared to N. CONCLUSION: HFB associated with neurorrhaphy enhanced muscle and nerve regeneration, attenuating muscle atrophy and fibrosis.