Insulin-like growth factors I and II expression in the healing wound

Demonstrating temporal variation in the expression of messenger RNA (mRNA) for growth factors may give some indication as to whether growth factor synthesis is regulated in wound healing. The aim of this study was to evaluate the expression of insulin-like growth factors (IGF) I and II in the wound. Two wound models, an incisional model and a subcutaneous sponge implant model, were used in this study. The RNA was extracted and reverse transcribed and mRNA was amplified using polymerase chain reaction (PCR). Semiquantitation of PCR products was accomplished using [3H]dGTP incorporation. Levels of expression for both IGF-I and -II were found to be low in unwounded skin and at 12 hr postwounding. However, in both wound models expression increased substantially from 1 to 21 days postwounding. Both factors also were found to be expressed by fibroblasts and polymorphonuclear leukocytes (PMN). Additionally, two transcripts were found for IGF-II, the larger of which appeared to be specific for PMN and possibly cells involved in angiogenesis. Levels of message expressed in healing wounds for IGF-I and -II appear to be regulated with the highest levels of message found at time points coinciding with fibroblast predominance in the wound. Since fibroblasts are known to both secrete and respond to IGF-I, it is possible that IGF-I and IGF-II are acting to influence fibroblast differentiation and function in the later stages of wound healing.