Effect of 670-nm laser therapy and dexamethasone on tissue repair: a histological and ultrastructural study

Abstract

Objective: In this study we investigated the role of extracellular matrix elements and cells during the wound healing phases following the use of low-level laser therapy (LLLT) and anti-inflammatory drugs. Background Data: There are few scientific studies that characterize the possible interactions of LLLT and anti-inflammatory medications. Materials and Methods: Thirty-two rats submitted to a wound inflicted with a 6-mm-diameter punch. The animals were divided into four groups: sham treated, those treated with the GaAlAs laser (4 J/cm2, 9 mW, λ = 670 nm, spot size 28.27 × 10−2 cm2), those treated with dexamethasone (2 mg/kg), and those treated with both LLLT and dexamethasone. After 3 and 5 d, the cutaneous wounds were assessed by histopathology using polarized light and ultrastructural assessment using transmission electron microscopy. Changes seen in polymorphonuclear inflammatory cells, edema, mononuclear cells, and collagen fiber deposition were semi-quantitatively evaluated. Results: The laser-treated group demonstrated increased collagen content and better arrangement of the extracellular matrix (p < 0.05). Fibroblasts in these tissues were increased in number and were more synthetically active. In the dexamethasone group, the collagen was shown to be non-homogenous and disorganized, with a scarcity of fibroblasts. In the group treated with both types of therapy, fibroblasts were more common and they exhibited vigorous rough endoplasmic reticulum, but they had less collagen production compared to those seen in the laser group. Conclusion: LLLT alone accelerates post-surgical tissue repair and reduces edema and the polymorphonuclear infiltrate even in the presence of dexamethasone.