Activation of latent TGF-β1 by low-power laser in vitro correlates with increased TGF-β1 levels in laser-enhanced oral wound healing

The term Laser "Photobiomodulation" was coined to encompass the pleiotropic effects of low-power lasers on biological processes. The purpose of this study was to investigate whether transforming growth factor (TGF)-beta had a role in mediating the biological effects of low-power far-infrared laser irradiation. We assayed for in vitro activation using various biological forms of cell-secreted, recombinant, and serum latent TGF-beta using the p3TP reporter and enzyme-linked immunosorbent assays. We demonstrate here that low-power lasers are capable of activating latent TGF-beta 1 and -beta 3 in vitro and, further, that it is capable of "priming" these complexes, making them more amenable to physiological activation present in the healing milieu. Using an in vivo oral tooth extraction-healing model, we observed an increased TGF-beta 1, but not beta 3, expression by immunohistochemistry immediately following laser irradiation while TGF-beta 3 expression was increased after 14 days, concomitant with an increased inflammatory infiltrate. All comparisons were performed between laser-irradiated wounds and nonirradiated wounds in each subject essentially using them as their own control (paired T-test p < 0.05). Low-power laser irradiation is capable of activating the latent TGF-beta 1 complex in vitro and its expression pattern in vivo suggests that TGF-beta play a central role in mediating the accelerated healing response.