The role of dermal fibroblasts in the expression of radiation-induced damage to the skin was studied. Fibroblasts from neonatal mice were cultured, harvested, and injected into full-depth surgical incisions in the dorsal area of mouse skin, which had been previously locally irradiated by 18 Gy X rays. As a control, cells irradiated with a dose of 20 Gy were also injected. The effect of radiation and fibroblast implants on the gain of skin wound strength was assayed. In an additional experiment freshly isolated cells were implanted. Two weeks following wounding the irradiated skin had reached only about a third of the strength of unirradiated skin. A significant increase of wound strength in irradiated skin was observed when 1.5-2 x 10(6) cultured fibroblasts or freshly isolated fibroblasts were injected into the 20-mm-long wound bed. Irradiated cells had significantly less effect. This suggests that implanting isolated syngeneic cells may "rescue" wounds from the effect of prior irradiation. Semiquantitative immunohistology of types I and III collagen was performed in parallel using a video image digitizing system. Levels of both types I and III collagen were altered in the dermis and the wound tissues in irradiated skin, but the implant of cultured fibroblasts did not affect notably the total levels and the disposition of the two collagen isotypes.