Photobiomodulation Therapy Enhances Peripheral Nerve Repair by Restoring Nerve Growth Factor Levels and Increasing Myelin Protein Zero Expression After Chronic Constriction Injury in Rats.

Neuropathic pain is a chronic condition frequently associated with peripheral nerve injury and is characterized by significant structural and molecular alterations. Photobiomodulation therapy (PBMT) has demonstrated analgesic and anti-inflammatory effects; however, its influence on neurotrophic and myelin-associated repair mechanisms remains incompletely understood. The aim of this study was to investigate the effects of PBMT on ultrastructural, morphometric, and molecular changes induced by chronic constriction injury (CCI) of the sciatic nerve in male rats, with an emphasis on NGF and P0 expression. Neuropathy was induced using the CCI model of the sciatic nerve. PBMT was initiated 14 days after injury and administered in ten sessions using an infrared 904 nm laser. Transmission electron microscopy, morphometric analysis, immunofluorescence, and Western blot analyses were performed to evaluate neural regeneration and the expression of NGF and P0. Animals subjected to CCI exhibited ultrastructural changes consistent with Wallerian degeneration, accompanied by reduced NGF and P0 expression in the sciatic nerve. In contrast, PBMT markedly preserved nerve morphology, restored NGF expression, and significantly increased P0 protein levels. Together, these findings demonstrate that PBMT enhances peripheral nerve repair by promoting both molecular and structural mechanisms involved in axonal regeneration and myelin restoration. Restoration of NGF expression and increased P0 protein expression suggest that these mechanisms contribute to the regenerative effects of PBMT, supporting its potential as a safe, noninvasive therapeutic strategy for peripheral neuropathies.