Role of T-lymphocytes in Radiation-impaired Wound Healing

Radiation impairs healing, although the underlying mechanisms are not clearly defined. Tlymphocytes have been shown to be critical for wound healing. We hypothesized that radiation-impaired healing may affect different subtypes of T cells. The aim of the study. We studied the effect of local electron irradiation on standard parameters of dermal wound healing in rats and correlated the outcome of healing with the expression of different lymphocyte subtypes in the wound. Material and methods. Groups of 10 rats were irradiated using single dose 12 or 24 Gray electron radiation at the dorsal skin. Control rats were sham-irradiated. On day 5, a skin incision in the irradiated area was performed and polyvinyl alcohol sponges were inserted subcutaneously. Rats were sacrificed 10 days later to determine the wound breaking strength and reparative collagen deposition. Blood lymphocytes were analyzed by FACS. Immunohistochemistry was performed on wound sections. Results. Irradiation significantly reduced wound collagen deposition and wound breaking strength (p <0.05), leading to a 78% reduction in collagen deposition and 47% reduction in breaking strength in 24 Gy animals. Blood lymphocytes were not affected by electron-irradiation, suggesting that the wound was not affected by radiation-induced systemic effects. Impaired healing was reflected, however, in increased expression of wound CD8 cells and decreased expression of CD25 (IL-2 receptor) (p<0.01). No effect was seen on wound CD4 cells. In addition, the ratio of CD4/CD8 was significantly decreased (p<0.05). Conclusions. Radiation-impaired healing is reflected in impaired expression of wound lymphocyte subtypes. Altered lymphocyte subtypes may affect the outcome of healing in irradiated wounds.