Low-level laser therapy increases transforming growth factor-beta2 expression and induces apoptosis of epithelial...

Low-level laser therapy (LLLT) has been reported to modulate the healing of wounds by inducing an increase in mitotic activity, fibroblast number, synthesis of collagen, and neovascularization.

In the present study we evaluated the effect of LLLT on expression of TGF-beta(2), an immunosuppressive cytokine, at the site of tissue repair, using an experimental rat model to study cutaneous wound healing. In addition, we also investigated the presence of apoptotic cells in epithelial and connective tissue.

Thirty male Wistar rats were divided into two groups: group 1, which was subjected to surgical skin wounds only (n = 15), and group 2, which was subjected to surgical skin wounds followed by LLLT (n = 15). In group 2, the LLLT was given with these parameters: 15 mW of power, a dose of 3.8 J/cm(2), for 15 sec for three applications. At 10 d post-surgery and laser application the animals were sacrificed with an overdose of anesthetic and tissue samples from the wounds were submitted to immunohistochemistry and in-situ detection of apoptosis.

Most of the inflammatory cells and fibroblasts were TGF-beta(2)-positive, and many apoptotic epithelial cells and fibroblasts were seen in the tissue samples from the LLLT-treated animals. However, a few apoptotic epithelial cells and fibroblasts were also seen in the samples obtained from control animals.

Our results indicate that LLLT may be an important inducer of apoptosis during the process of tissue repair. In addition, we demonstrated that LLTT has an immunomodulatory effect on TGF-beta(2) expression at sites of wound healing.