Expression of tissue inhibitor of metalloprotease 3 is reduced in ischemic but not neuropathic ulcers from patients with type 2 diabetes mellitus

Diabetic foot ulceration remains one of the most common and most serious consequences of diabetes. Persistently high levels of matrix metalloproteases (MMPs) contribute to wound chronicity. Our aim was to assess the concentrations of MMPs and tissue inhibitors of metalloproteinases (TIMPs) in neuropathic and ischemic diabetic foot ulcers by analyzing biopsy samples. In this study, biopsies were taken from 35 diabetic foot ulcers of type 2 diabetes mellitus patients and distinguished in neuropathic (n = 14) or ischemic (n = 21). Zymography assay was utilized for the analysis of MMP-2 and MMP-9 activity. TACE activity was evaluated by a specific fluorimetric assay. mRNA levels of MMPs as well as TIMPs were detected using quantitative real-time polymerase chain reaction. The activity of MMP9 and A Disintegrin and A MetalloProtease Domain 17/TNF-Alpha Converting Enzyme (ADAM17/TACE) was significantly increased in ischemic compared to neuropathic biopsies. No differences were detected between both groups for the mRNA levels of MMPs as well as of ADAMs. However, TIMP3 mRNA expression was decreased in ischemic samples. The combination of increased activity of MMP9 and ADAM17/TACE with decreased concentrations of TIMP-3 mRNA expression in ischemic diabetic foot ulcers compared to neuropathic samples suggests that the increased proteolytic environment may represent a causative factor in the ulcer progression. New treatment strategies for healing diabetic foot ulcers could be directed toward increasing levels of TIMP3.