Equine laminitis: membrane type matrix metalloproteinase-1 (MMP-14) is involved in acute phase onset

Abstract

Reasons for performing study: Enzymatic separation at the hoof lamellar dermal-epidermal interface may play a role in the development of laminitis and characterising and locating matrix metalloproteinases (MMPs) and their inhibitors (tissue inhibitors of MMPs or TIMPs) in lamellar tissues may further understanding of pathogenesis.

Objectives: To clone and sequence the cDNA encoding lamellar MMP-14 and TIMP-2, and quantify their transcription in normal and laminitic tissue; and to develop antibody to locate MMP-14 in lamellar tissues.

Methods: Tissue samples were obtained from an oligofructose induced model of laminitis. Total RNA was isolated, amplified by RT-PCR, cloned into a vector and sequenced. Real-time PCR was used to quantify MMP-14 and TIMP-2 expression. Rabbit anti-equine MMP-14 antibody was developed to analyse MMP-14 proteins from hoof tissues.

Results: Immunohistochemistry detected MMP-14 in the cytoplasm of normal lamellar basal and parabasal cells in close proximity to the lamellar basement membrane. In laminitis affected tissue MMP-14 immunostaining was depleted in lamellar basal cells. Quantitative real-time PCR showed MMP-14 and TIMP-2 expression significantly (P<0.05) elevated and lowered respectively in laminitis affected tissues.

Conclusion: MMP-14, located in the cytoplasm of normal lamellar basal cells, disappears during laminitis development. The pathology of laminitis is associated with increased and lowered transcription of MMP-14 and TIMP-2, respectively.

Potential relevance: Enzymes have a role in laminitis pathology and inhibition of their activity may prevent laminitis.