Electron irradiation slows down wound repair in rat skin: a morphological investigation

To date, there have been few morphological investigations of the effect of electron radiation on the healing of skin wounds in rats. The present morphological study examines the wound repair process in electron-irradiated rat skin by electron microscopy. Standardized, full-thickness, incisional wounds were made in the lower dorsal skin of animals which had been locally irradiated with 9.6 Gy electron radiation 7 days previously. The irradiation dose was maximal at 3 mm depth. Twenty-four rats were used in the investigation; 12 were irradiated and 12 sham-irradiated. Three rats from each experimental group were killed at 1, 3, 7 and 14-day time intervals after wounding. The morphological effect of electron irradiation on the repair of each wound was investigated by light microscopy (LM) and scanning electron microscopy (SEM). New granulation tissue visualized by SEM was quantified using computerized image analysis. The results suggest that a single, partial-body, controlled depth dose of electron irradiation delays wound repair. LM showed that there is a depression of the inflammatory cell and tissue exudate response, slowing of epithelial migration, and a decrease in fibroblast representation, together with a delay in the formation of collagen bundles. Granulation tissue formation was impaired up to 7 days post-wounding, but was restored to around control values by day 14, indicating that healing was delayed. However, as the healing of normal tissue was not prevented, this study supports a preoperative role for the use of low-dose electron irradiation therapy for the treatment of electron-sensitive superficial pathologies in surgical practice.