Presence of neutrophil myeloperoxidase in lamellar tissue of horses with laminitis induced using a hyperinsulinemic model

Laminitis is a pathology of the equine digit resulting in failure of the dermo-epidermal interface. Inflammation is likely a central player in its pathophysiology. Neutrophil activation and the presence of myeloperoxidase have been observed in the black walnut heartwood extract model, used to investigate sepsis-related laminitis. However, less is known about the role of neutrophil activation in the prolonged euglycemic hyperinsulinemic clamp (pEHC) model. This model is used to investigate the pathophysiology of laminitis related to endocrine disturbances like hyperinsulinemia encountered in pituitary pars intermedia dysfunction and equine metabolic syndrome.
Five horses were included in this study and randomly assigned to a control group (n = 2) and a pEHC group (n = 3). Histological sections of lamellar tissue from all horses were obtained and immunohistochemically stained for myeloperoxidase and counterstained with hematoxylin-eosin. The sections were examined for histopathological evidence of laminitis and myeloperoxidase.
Histopathological changes that characterize insulin-induced laminitis and increased presence of myeloperoxidase, especially in the dermal lamellae, were observed in histologic sections of pEHC-treated horses compared to control horses.
Neutrophil activation with myeloperoxidase release may play a role in the pathophysiology of endocrinopathic laminitis. The implications of this finding warrant further investigation.