Biochemical changes in injured sciatic nerve of rats after low-level laser therapy (660nm and 808nm) evaluated by Raman spectroscopy.

Abstract

The aim of this study was to identify biochemical changes in sciatic nerve (SN) after crush injury and low-level laser therapy (LLLT) with 660nm and 808nm by Raman spectroscopy (RS) analysis. A number of 32 Wistar rats were used, divided into four groups (control 1, control 2, LASER 660nm, and LASER 808nm). All animals underwent surgical procedure of the SN and groups control 2, LASER 660nm, and LASER 808nm were submitted to SN crush damage (axonotmesis). The LLLT in the groups LASER 660nm and LASER 808nm was applied daily for 21 consecutive days (100mW, 30s, 133J/cm2 fluence). The hind paw was removed and the SN was dissected and positioned on an aluminum support to collect dispersive Raman spectra (830nm excitation, 30s accumulation). To estimate the biochemical changes in the SN associated with LLLT, the principal component analysis (PCA) was applied. The Raman spectra of the sciatic nerve fragments showed peaks of the major biochemical components of the nerve, especially sphingolipids, phospholipids, glycoproteins, and collagen. The spectral features identified in some of the principal component loading vectors are referred to the biochemical elements present on the SN and were increased in the groups treated with LLLT, mainly lipids (sphingo and phospholipids) and proteins (collagen)-constituents of the myelin sheath. The RS was effective in identifying the biochemical differences in the SN after the crush injury, and LASER 660nm was more efficient than the LASER 808nm in cell proliferation and repair of the injured SN.