Nonthermal Effects of Nd:YAG Laser on Biological Functions of Human Skin Fibroblasts in Culture

Previous studies have indicated that laser can selectively affect the biological functions of cells. In the present study, the role of a thermal component in laser-induced alterations in the biology of human skin fibroblasts was examined. Cells were cultured on 96-well tissue culture plates, subjected to treatment with the Nd:YAG laser (wavelength 1,064 nm), and the temperature of the medium was monitored by a microprobe connected to a telethermometer . For comparison, parallel cultures were heated to the same temperatures by tungsten-halogen lamp. The cell cultures were analyzed for collagen synthesis by incubating the cultures with [3H]proline, and the collagen production was assayed by the synthesis of nondialyzable [3H]hydroxyproline. The rate of DNA replication was also determined by measuring the uptake of [3H]thymidine. A marked decrease of collagen production and thymidine incorporation was noted in the cultures subjected to Nd:YAG laser. No such decreases were noted in cultures heated to the corresponding temperatures by tungsten-halogen lamp. The results thus indicate that the biochemical alteration caused by the Nd:YAG laser in human fibroblast functions cannot be explained on the basis of thermal effects.