RESUMO
The stability of peptide growth factors exposed to fluids from healing surgical wounds and from nonhealing chronic wounds was examined in vitro. (125)I-Labeled transforming growth factor-beta1 or platelet-derived growth factor-BB was incubated with fluids from healing surgical wounds and fluids from venous stasis or pressure ulcers. Fluids from healing surgical wounds had no appreciable effect on the level of (125)I corresponding to intact growth factor. In contrast, incubation with fluids from several venous stasis or pressure ulcers resulted in significant degradation of these growth factors. Degradation was blocked by broad-spectrum serine proteinase inhibitors and by specific inhibitors of neutrophil elastase. Levels of elastase activity in wound fluids correlated with the ability to degrade peptide growth factors. Further comparisons showed qualitative and quantitative differences in the endogenous proteinase inhibitors, alpha2-macroglobulin and alpha1-antiproteinase. These results could explain, in part, the variable growth factor levels which have been found in chronic wounds. More importantly, the ability of some chronic nonhealing wounds to rapidly degrade exogenously added growth factors has important implications with regard to past and future clinical attempts to use peptide growth factors to treat these types of problem wounds.
RESUMO
Open wounds in the fetal rabbit do not heal by contraction and actually expand between 60% and 90% over a period of 5 days. Experiments were carried out to determine whether transforming growth factor-beta1 can reduce expansion of open wounds in the fetal rabbit. This study was based on the concept that transforming growth factor-beta1 causes differentiation of fibroblasts into contractile fibroblasts or "myofibroblasts." To test this hypothesis, pregnant New Zealand White rabbits underwent laparotomy and hysterotomy on day 24 of gestation. A circular full-thickness cutaneous wound was made on the back of each fetus. After wounding, either vehicle alone or vehicle with transforming growth factor-beta1 was applied topically to the wound site, and each fetus was then returned to the uterus. The hysterotomy and laparotomy were closed in standard fashion. On postoperative day 5, fetuses were harvested by repeat Cesarean section. Wound areas were determined from photographs, calculated as percentage of original wound size, and expressed in square millimeters. In addition, a portion of each wound was fixed and processed for histologic and immunohistochemical analysis. At harvest, the control wounds had expanded by an average of 87% of the original area. In marked contrast, the transforming growth factor-beta1-treated wounds had only expanded an average of 16%. Thus, transforming growth factor-beta1 significantly decreased the area of the open fetal wounds compared with control (p < 0.001). By histologic examination, no significant difference was found between the test group and the control group with regards to inflammation, neovascularization, collagen deposition, elastin content, glycosaminoglycan content, or hyaluronic acid content. Most notably, however, there was an increased density of fibroblasts in the transforming growth factor-beta1-treated group. In addition, immunohistochemical staining with an anti-alpha-smooth muscle actin antibody showed the presence of contractile fibroblasts in the wound margins in the transforming growth factor-beta1-treated group but failed to show any positive-staining fibroblasts in the matrices of the control group. These results indicate that open wounds in the fetal rabbit treated in vivo with transforming growth factor-beta1 were significantly smaller than control wounds. This process appears to result from the recruitment and differentiation of normal dermal fibroblasts into contractile fibroblasts containing alpha-smooth muscle actin.
