Macrophage responsiveness to light therapy with varying power and energy densities

Abstract

Macrophages are a source of many important mediators of wound repair. Cells of an established macrophage-cell line (U-937) were exposed in vitro to an 820 nm light source which was both coherent and polarized, the power densities used being either 400 mW/cm2 or 800 mW/cm2. The irradiation times were such that the energy densities to which the cells were exposed were 2.4 and 7.2 J/cm2 for both probes. Twelve hours after exposure the macrophage-conditioned medium was removed and placed on 3T3 fibroblast monolayers. Fibroblast proliferation was assessed over a four-day period. By four days after the addition of medium conditioned by macrophages exposed to an energy density of 2.4 J/cm2, there was a statistically significant difference in fibroblast number between the 400 mW/cm2 and 800 mW/cm2 treatments, 800 mW/cm2 producing greater cell proliferation. However, there was no significant difference between the effects of sham irradiation and 400 mW/cm2. In contrast, after the addition of medium conditioned by macrophages exposed to an energy density of 7.2 J/cm2, 400 mW/cm2 treatment produced a significantly greater increase in fibroblast number than sham irradiation. There was no significant difference in cell number between the sham irradiated and 800 mW/cm2 irradiated samples, although there was a signilicant difference between the 400 mW/cm2 and the 800 mW/cm2, 400 mW/cm2 producing greater cell proliferation. © 1991, International Phototherapy Association. All rights reserved.