Repair of facial nerve injury in rats with lipid nanoparticles-encapsulated mitochondria

Background　Since early mitochondrial dysfunction constrains facial nerve regeneration, improving the therapeutic outcomes of mitochondrial transplantation through optimized delivery methods has become a primary research focus.Objective　To construct lipid nanoparticles (LNP)-encapsulated engineered mitochondria (Mito@LNP) and evaluate their reparative effects in a rat buccal branch facial nerve crush injury model.Methods　LNP was prepared by thin film hydration-extrusion method. Mitochondria were isolated from human umbilical cord mesenchymal stem cells (hUCMSC) and formulated into Mito@LNP. In vitro, PC12 cells were used to assess cytotoxicity, cellular uptake, and protection against H₂O₂-induced oxidative damage. In vivo, a rat buccal branch facial nerve crush model was established, and Mito@LNP was administered locally via subepineurial injection at the injury site. Small animal in vivo optical imaging system was employed to track mitochondrial distribution. Whisker movement analysis, electrophysiological testing, and immunofluorescence staining were performed to evaluate evaluate its neural repair effects.Results　 Mito@LNP was successfully fabricated, achieving a mitochondrial encapsulation efficiency of 89.4%. Compared with free mitochondria, LNP encapsulation enhanced mitochondrial uptake by PC12 cells (P＜0.05). Under oxidative stress, Mito@LNP more effectively maintained ATP production (P＜0.001) and mitochondrial membrane potential (P＜0.05) in PC12 cells, thereby markedly improving cell viability (P＜0.05). In vivo tracking indicated stronger retention and accumulation of Mito@LNP at the injured nerve (P＜0.05). Rats treated with Mito@LNP showed substantially better recovery of whisker function (P＜0.001) and compound muscle action potential (CMAP) parameters (P＜0.05) than those receiving free mitochondria. Immunofluorescence staining further demonstrated that Mito@LNP significantly upregulated NF200 (P＜0.001) and S100β (P＜0.05) expression in injured nerve tissue.Conclusion　Mito@LNP markedly enhanced repair and functional recovery after facial nerve crush injury in rats by improving mitochondrial delivery efficiency, and exhibited superior efficacy compared with free mitochondria.