Laminar leukocyte accumulation in horses with carbohydrate overload-induced laminitis.

The study investigates the presence of leukocytes and signs of epidermal stress in horses with laminitis induced by carbohydrate overload, distinguishing it from laminitis caused by black walnut extract. It proposes that leukocyte infiltration occurs before significant histological changes, suggesting leukocytes to be a cause as opposed to a result of structural degradation.

Objective and Methods of the Study

• The objective of the research was to determine the presence of leukocytes and signs of epidermal stress or injury in the hoof’s laminar tissue in cases of laminitis induced by carbohydrate overload in horses.
• There were twenty-four adult horses involved in the study, divided into groups: the developmental time point (DTP) group, the onset of lameness (LAM) group, and a control group.
• These groups were used to model carbohydrate overload and were examined with immunohistochemistry (labelling of specific immune cells) for cell markers calprotectin (CP) and the monocyte-specific marker (CD163).

Study Results

• The DTP group registered an increase in CP(+) leukocytes, about 7.8 times compared to the control group. In the LAM group, there was an even higher count of CP(+) leukocytes, approximately 108.5 times compared to the control group. Additionally, there was a mild increase in CD163(+) cell counts.
• The onset of lameness was characterized by increased CP epidermal signal, indicating either epidermal stress or injury. However, the evidence of basement membrane detachment, a clear sign of a severe pathological condition, was minor, appearing in only half of the horses in the LAM group.
• These findings suggested that the maximal rate of leukocyte infiltration in the hoof’s laminar tissue and epithelial stress occurred at the onset of lameness in the carbohydrate overload model.

Conclusions and Implications

• The study concluded that the temporal pattern of leukocyte infiltration in carbohydrate overload-induced laminitis is distinctly different from the black walnut extract (BWE) model of laminitis.
• Whereas in the BWE model, leukocyte infiltration clearly precedes epithelial stress, in the carbohydrate overload model, both occur at the onset of lameness.
• The study suggests that the presence of leukocytes in the laminar tissue of the hoof can be a cause of structural failure and degradation and not merely a reaction to it. This finding could have implications for the understanding and potential treatment of laminitis, a serious and painful condition in horses.