Biochemical changes in the skin and laminar tissue from horses with experimentally-induced laminitis

Abstract

The pathogenesis of acute laminitis in horses is complex and poorly understood. As a component of the integumentary system, the hoof, like the skin, is composed of epidermis, dermis, and subcutaneous tissue. For this reason, it may be possible to identify alterations occurring in the skin that correlate with derangements in the laminae. Thus, examination of these two tissues may allow identification of pathologic mechanisms affecting the integument during the onset of laminitis. The equine hoof is a specialized modification of the integumentary system and includes interdigitations of the dermis and epidermis. The purpose of this study was to further define the presence of leukocytes and their enzymatic products in the skin and laminar tissues of horses administered black walnut heartwood extract and compare those findings to horses administered purified lipopolysaccharide (LPS). Data obtained in the present study indicate that CD13-positive leukocytes and MMP-9 expression and activity, increased in laminar tissue, are also increased in skin from horses with experimentally induced laminitis. Additionally, these increases were not evident in horses treated with LPS. Results of the LPS group were not significantly different from Control tissues. The results of this study show that the pattern so leukocyte emigration are similar in skin and laminar tissue collected from the black walnute iv extract model. Furthermore, these biochemical events are not occurring in experimental endotoxemia. The ease with which skin specimens can be obtained, compared with the collection of laminar tissue, may facilitate identification of horses at increased risk of developing acute laminitis or for assessing the efficacy of new treatment modalities designed to minimize activation and extravasation of WBCs.