PLATELET-DERIVED GROWTH-FACTOR LEVELS IN WOUNDS OF DIABETIC RATS

Delayed wound healing is a troublesome complication of Diabetes. Results from recent investigations concerning the potential cellular and molecular mechanisms responsible for diabetic wound healing deficiency are preliminary in nature. Some studies have demonstrated that direct application of certain growth factors/cytokines can facilitate wound healing in diabetic models. It is possible that refractory diabetic wounds are the result of deficiencies in growth factors/cytokines important for the normal wound healing process. Platelet-Derived Growth Factor (PDGF) levels were examined by radioimmunoassay in wound tissue of normal and diabetic rats (streptozotocin-induced diabetes). Immunohistochemical analysis was utilized to localize and characterize PDGF immunopositive cells at the wound site of normal and diabetic animals. At the wound site, normal animals demonstrated significantly elevated PDGF levels compared to diabetic animals at 5 days post-wounding (no differences were observed in the spleen or contralateral control tissue). There appeared to be a visible increase in PDGF immunopositive cells at the wound site in both experimental and control groups. By day 10 post-wounding, PDGF levels at the wound site in normal animals were reduced becoming similar to PDGF levels in diabetic animals. This corresponded to an apparent reduction of PDGF immunopositive cells in both groups (similar to baseline levels). PDGF levels in both groups remained stable until day 20 post-wounding when a significant elevation of wound site PDGF levels occurred in the diabetic group. The findings suggest that absence of an initial increase in PDGF may play an important role in poor wound healing observed in diabetic animals. The reduction in PDGF may be related to decreased cellular PDGF production rather than a lack of PDGF-producing cells. Perhaps the diabetic state inhibits cellular PDGF gene expression signaled by wounding or interferes with normal PDGF expression at the wound site.