Effect of rapamycin on wound healing: an experimental study

The aim of this study was to investigate the effects of rapamycin (RAPA) on the healing of bladder and abdominal wound closures. Fourteen male Sprague Dawley rats were randomized to receive either RAPA (3 mg/d) or placebo. A midline laparotomy was performed. The bladder was cut and closed with 4-0 Vicryl in a double layer. The fascia was closed with 0 nylon suture, and the skin closed with a subcuticular 2-0 nylon suture. The mean RAPA level was 9.1 ng/mg. Eosinophil and neutrophil infiltration, and the presence and degree of myofibroblast proliferation were significantly higher in the bladder, fascia, and dermis of the control group. Lymphocyte infiltration was similar in each group. Mean microvessel density as well as the percentage of cells expressing vascular endothelial growth factor in the bladder, fascia, and dermis were significantly lower among the RAPA group. Both proliferating cell nuclear antigen labeling indices for inflammatory cells in the fascia, dermal fibroblasts, and epithelial cells in the placebo group were significantly higher. No difference was observed for hydroxyproline levels in both the bladder and fascia between the groups. In conclusion, we found that RAPA treatment affected all steps of the wound healing process by decreasing the inflammatory cell number, angiogenesis, and myofibroblast proliferation, so the wound healing process was delayed and consequently the tensile strength of the wound decreased.