Natalia Labraña-Ojeda; Camila Isla-Medina; Nicolás Vidal-Seguel & Enrique Montiel-Eulefi

The sciatic nerve (SN), following a compression injury, undergoes either a regeneration process or fibrosis as a consequence of dysregulated inflammation. Lactic acid (LA) has been shown to modulate the inflammatory response in the peripheral nerve by promoting the macrophages anti- inflammatory phenotype. Macrophages play a fundamental role in the Wallerian degeneration process by clearing cellular debris and degrading collagen in the damaged area, facilitating a clearance phenomenon prior to the remodeling of the injured nerve region. Collagen, which constitutes nearly half of the nerve tissue proteins, has a dual role in regeneration: while type I collagen inhibits axonal growth and promotes fibrosis, type III collagen is associated with cell survival and regenerative processes. This study analyzes the expression of type I and type III collagen during sciatic nerve remodeling to seven days, post-injury, using Sirius Red (SR) staining in Sprague Dawley rats subjected to compression (15 kg/ 10 min) and treated with intraneural injection of LA. Collagen quantification was performed through image analysis of SR-stained histological sections. The results demonstrated that intraneural LA injection reduces total collagen and increases type III collagen at seven days, post-injury, suggesting that LA not only decreases fibrosis but also fosters a regenerative environment through the induction of type III collagen. This research provides novel insights into the role of LA in the regenerative therapy of nerve injuries.

LABRAÑA-OJEDA, N.; ISLA-MEDINA, C.; VIDAL- SEGUEL, N. & MONTIEL-EULEFI, E. Modulation of type I and III collagen by lactic acid in sciatic nerve remodeling after compression injury: Histochemical analysis with sirius red in Sprague-Dawley rats. Int. J. Morphol., 43(4):1337-1343, 2025.