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While much research has focused on the theory that reduced blood flow resulting in poor tissue oxygenation is the fundamental cause of laminitis, researchers from Dr. Chris Pollitt’s laboratory in Australia have explored a new theory on the cause of laminitis at the cellular level.
Sections of intact laminae from normal hoof tissue were prepared in the laboratory to test the structural integrity of the lamellar junction. These tissue sections were treated with one of several gram negative or positive bacterial broth cultures, then the amount of force necessary to separate the laminae was measured and the tissues were examined histologically.
Results indicate that bacterial exotoxins are capable of activating tissue enzymes (matrix metalloproteinases or MMPs) at the cellular level. Microscopic examination of the tissues demonstrated the MMPs weaken the lamellar bond at the basement membrane, causing separation of the laminae in the same manner observed with clinical laminitis.
These experiments are thought to parallel what naturally occurs when streptococcal bacteria proliferate in the caecum and colon following grain overload or the ingestion of excessive amounts of lush grass. The authors suggest this theory provides a unifying causal mechanism for understanding carbohydrate- induced laminitis. Future research that identifies specific exotoxins involved could lead to preventive therapies.
— Mungal BA, Kyaw-Tanner M, Pollitt CC. In Vitro Evidence For A Bacterial Pathogenesis Of Equine Laminitis. Veterinary Microbiology 2001;79:209-223.
In this experimental trial, perfusion of the front feet and distal limbs was…