Validation of a surgical wound healing model in Sprague-Dawley rats

MATERIALS AND METHODS: Two (2) full thickness skin incisions (50 mm in length) were created in the thoracolumbar area of adult male Sprague-Dawley rats and the wounds were sutured using a standardized suture pattern. Daily intramuscular saline and dexamethasone (4 mg/kg) injections were used as negative and positive controls, respectively. On Day 4 after surgery, rectangular skin samples were tested within 6 hrs of collection. Skin samples with standardized dimensions (15 X 40mm) were tested under tension until wound ruptured and the remaining ten (10) mm of wound was used for histology evaluation (H&E). The maximal tension was recorded for each skin sample and compared between groups.

RESULTS: Mean tensile strength was 0.55N in saline-treated rats and 0.23N in dexamethasonetreated rats (p<0.05). A significant reduction in body weight on Day 4 when compared to pretreatment was also noted for the dexamethasone group (p<0.0005) but no statistically significant difference was noted for saline-treated rats. Histology was compatible with a delayed wound healing in dexamethasone-treated rats.

CONCLUSION: The model identified a dexamethasone-induced reduction in tensile strength with characteristic histological changes. This rat model is considered adequate for preclinical evaluation of perioperative wound healing.