Laminar inflammatory events occur to a similar extent in the hind lamina as in the front in the CHO model of laminitis.
Introduction
Laminitis most frequently affects the forelimbs of the horse and infrequently involves the hindlimbs. It is unknown if increased prevalence in forelimbs is due to greater forces sustained by forelimbs, or due to a difference in severity of pathologic events in the hindlimbs.
Materials and Methods
Sixteen horses were administered carbohydrate; these horses were anesthetized either after a two degree increase in rectal temperature (DEV) or at the onset of Obel grade 1lameness (OG1). Control horses (CON) were anesthetized 24 hours after administration of deionized water. Quantitative real-time PCR for selected pro-inflammatory mediators was performed on the collected laminar tissue in addition to MAC387 immunohistochemistry for leukocyte migration determination. The data were analyzed non-parametrically to compare groups.
Results
Similar increases in laminar MAC387-positive leukocytes and laminar mRNA concentrations (P < 0.05) for IL-1β, IL-6, COX-2, CXCL1 and CXCL8 were present in hindlimb and forelimb laminae from horses with OG1 lameness (vs. CON). CXCL1 and CXCL8 were also similarly increased in forelimb and hindlimb laminae at the DEV time (vs. CON).
Discussion
This suggests that additional factors such as weight may play an important role in the ultimate failure that occurs more frequently in the front feet.
Clinical Relevance
Evidence of inflammation in the hind lamina suggests that it should be addressed in the septic horse at risk for laminitis; however, laminitis may be less likely to occur due to other factors such as weight bearing.
Conclusions
Laminar failure is likely to require not only inflammatory injury to cellular structures, but also downward force causing separation of the injured laminae.
1The Ohio State University College of Veterinary Medicine, Columbus, OH
2University of Missouri College of Veterinary Medicine, Columbia, MO
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