Histopathology of insulin-induced laminitis in ponies.
Authors: Asplin, Patterson-Kane, Sillence, Pollitt, Mc Gowan
Journal: Equine veterinary journal
Summary
# Editorial Summary Insulin-induced laminitis develops through mechanisms distinctly different from sepsis-associated or mechanical laminitis, lacking the systemic inflammatory markers typically observed in other forms of the disease. Asplin and colleagues induced hyperinsulinaemia in five ponies whilst maintaining normal blood glucose for approximately 55 hours, then examined lamellar tissue histologically using standardised quantitative measurements and immunostaining for inflammatory markers. Rather than the widespread basement membrane destruction seen in other laminitis types, insulin-induced lesions presented with epidermal cell swelling, disorganisation and abnormal keratinisation, increased cellular proliferation and apoptosis concentrated at the axial region, and notably—elongation of secondary epidermal lamellae in the abaxial and middle zones without substantial basement membrane separation. The findings challenge the assumption that all laminitis involves similar pathophysiological mechanisms and suggest that metabolic laminitis requires distinct diagnostic and therapeutic approaches; practitioners managing insulin-resistant, hyperinsulinaemic horses should recognise that early lesions may not show classical signs of basement membrane failure, potentially explaining why some animals respond differently to conventional laminitis interventions.
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Practical Takeaways
- •Insulin-associated laminitis may have a fundamentally different mechanism than other forms, potentially requiring different diagnostic and treatment approaches beyond standard basement membrane disruption focus
- •Screening for hyperinsulinaemia in laminitis cases is clinically important, as these cases show distinct histological features and lack systemic inflammatory markers that typify other laminitis aetiologies
- •The preservation of basement membrane integrity in insulin-induced laminitis suggests that farriery and therapeutic approaches targeting laminar separation may need modification for hyperinsulinaemic cases
Key Findings
- •Insulin-induced laminitis in ponies lacked widespread basement membrane disintegration, distinguishing it histologically from other laminitis types
- •Secondary epidermal lamellae were significantly elongated in laminitic hooves relative to controls, with greatest elongation in abaxial and middle regions
- •Lesions included epidermal cell swelling, disorganisation, abnormal keratinisation, and increased mitotic activity and apoptosis, predominantly in axial regions
- •Inflammatory cells were present within lamellar dermis despite absence of systemic and intestinal inflammatory signs, suggesting local rather than systemic pathogenesis