Molecular and morphological studies on non-healing venous leg ulcers.

Abstract: Chronic skin ulcers are a major health problem and an increasing burden on health care providers. These ulcers have various underlying causes, such as venous or arterial insufficiency, diabetes, or vasculitis. Non-healing venous leg ulcers represent a condition characterized by excessive inflammation and presence of bacteria. The overall aim of this thesis has been to explore the pathogenesis of these ulcers, with particular focus on bacterial influence, capillary leakage, neutrophil efflux, and oxidative stress as well as cell growth. The results showed that cyclin A, a proliferation marker, was upregulated in the margins of chronic venous ulcers, at levels similar to those detected in acute wounds. Furthermore, several cell-associated proteoglycans were detected in the wound margins of venous ulcers, suggesting that epidermal cells in these ulcers are able to proliferate as well as express molecules important for cell homeostasis and growth. The venous ulcers contained significantly increased levels of chemotactic ?-defensins, as well as heparin binding protein (HBP), a factor known to induce capillary leakage. Secreted products of Pseudomonas aeruginosa, a bacterium often present in chronic ulcers, were found to induce release of HBP from human neutrophils. Chronic venous leg ulcers contained high levels of heme and porphyrin. Furthermore, a novel heme-scavenger, ?1-microglobulin, was identified in these ulcers. Taken together, the data suggests a possible link between bacterial presence, neutrophil activation and HBP-release in venous ulcers, which will help to explain the clinical observation of classic inflammatory signs such as high exudation, swelling, and erythema often accompanied by P. aeruginosa infected wounds. Thus, high HBP and defensin levels, promoting capillary leakage and chemotaxis, respectively, in concert with heme-mediated oxidative stress, may constitute a "vicious loop", which underlies the high inflammation noted in non-healing venous ulcers. These findings provide novel diagnostic markers and reinforce the view that future therapeutic approaches directed at venous ulcers should target inflammatory mechanisms and excessive bacterial influence.