Wound healing in ovariectomized rats: Effects of chemically modified tetracycline (CMT-8) and estrogen on matrix metalloproteinases-8,-13 and type I collagen expression

Cutaneous wound healing is a complex process involving interactions of vari ous cell types. Skin, in addition to certain other organs, is dependent on estrogen; and estrogen-deficiency is associated with impaired wound healing . Wound healing involves the action of collagenolytic matrix metalloprotein ases (MMPs). We investigated the expression and localization of collagenoly tic MMPs -8 and -13 by collagenase activity assay, Western immunoblot analy sis, in situ hybridization and immunohistochemical staining as well as type I collagen by hydroxyproline content analysis and immunohistochemical stai ning in cutaneous wounds from aged Sham and ovarioectomized (OVX) rats. Aft er wounding, OVX rats were treated with either placebo. chemically modified tetracycline-8 (CMT-8) or estrogen. We found that MMP-8 and MMP-13 mRNA we re expressed in wound epithelium of all samples examined as evidenced by Oz situ hybridization. Type 1 collagen, which was abundant in all groups exam ined, was decreased in OVX rats, but was increased by both CMT-8 and estrog en treatments to the level of Sham group. Hydroxyproline analysis revealed similar results. Western blot data showed that all forms of MMP-8 and MMP-1 3 were clearly reduced in the CMT-8 treated group com,pared to OVX. Analysi s of collagenolytic activity confirmed the decreased collagenolysis in skin wound extracts from CMT-treated rats when compared with shin wound extract s from OVX rats. Our results show for the first time thar MMP-8 mRNA and pr otein are expressed in rat wound epithelium. We further show that CMT-8 and estrogen have a beneficial effect on skin wound belling in OVX rats by inc reasing the collagen content and reducing thr MMP-mediated collagenolysis.