He-Ne laser irradiation affects proliferation of cultured rat Schwann cells in a dose-dependent manner.

Abstract

Schwann cell proliferation is considered an essential part of Wallerian degeneration after nerve damage. Laminin, an important component of the extracellular matrix and produced by Schwann cells, provides a preferred substrate for outgrowing axons. To study whether low energy (He-Ne) laser irradiation may exert a positive effect on nerve regeneration through an effect on Schwann cells, its effect was evaluated in vivo. Schwann cells were isolated from sciatic nerves of 4-5-day-old Wistar rates and cultured on 96-multiwell plates. The cells were irradiated by a He-Ne laser beam (632.8 nm, 5.98 mW) that was optically expanded to a beam width of 4 mm. During irradiation the plate was kept in an air-tight box equilibrated with humidified air containing 5% CO2 and kept at 37 degrees C. At three consecutive days, starting either at day 5 or day 8, cells were irradiated each day for 0.5, 1, 2, 5 or 10 min. Both cell number and laminin production were determined for each irradiation condition (n = 5) within one experiment. Schwann cells that were irradiated from day 8 on were hardly affected by laser irradiation. However, the proliferation of cells that were irradiated starting on day 5 was significantly increased after 1, 2, and 5 min of daily irradiation, compared to non-irradiated control cultures. The laminin production per cell of these Schwann cells was not significantly altered. From these results we conclude that He-Ne laser irradiation can modulate proliferation of rat Schwann cells in vitro in a dose-dependent manner.