In vitro evidence for a bacterial pathogenesis of equine laminitis.

The research article focuses on investigating the role of bacterial pathogens in the development of equine laminitis, a painful hoof condition in horses. The study, through the use of an in vitro laminitis model, shows that various bacteria types can activate enzymes that damage the hoof structure, indicating a bacterial direct cause of the disease.

Study Methodology

• The researchers used an in vitro laminitis explant model to conduct their research. This involved a laboratory model mimicking the disease conditions.
• They examined the effects of bacterial broths and specific bacterial enzymes, known as proteases, on the activation of Matrix Metalloproteinases (MMPs), a group of enzymes that affect the structure and function of tissues.
• The bacteria strains involved were four types of Gram-positive Streptococcus species and three types of Gram-negative bacteria.

Findings

• Activation of MMP-2 and MMP-9 was found to be dose-dependent, meaning the more bacteria involved, the greater the activation of these enzymes.
• If batimastat, a specific MMP inhibitor, blocked MMP activity and prevented the separation of lamellar explants, this was taken as confirmation of MMP activation
• Exposure to thermolysin and streptococcal pyrogenic exotoxin B (SpeB) resulted in lamellar explant separation, but only thermolysin could be inhibited by batimastat.
• The activation of MMPs from thermolysin and the bacterial broth was found to be cell dependent, suggesting they don’t function independently.

Implications

• Findings suggest Streptococcal species, when rapidly increased in the horse’s digestive tract in relation to carbohydrate induction, may directly cause laminitis through the production of certain exotoxins that activate MMPs present in the lamellar structure.
• Once these MMPs are activated, they can degrade vital components of the basement membrane, separating it from the epidermal basal cells and resulting in traditional laminitis pathology.
• The study provides a possibility for a unified cause of carbohydrate-induced equine laminitis, which has often been attributed to numerous other agents in the past.