Equine laminitis: loss of hemidesmosomes in hoof secondary epidermal lamellae correlates to dose in an oligofructose induction model: an ultrastructural study.
BACKGROUND
Light microscopical studies show that the key lesion of laminitis is separation at the hoof lamellar dermal-epidermal interface. More precise knowledge of the damage occurring in the lamellar basement membrane zone may result if laminitis affected tissue is examined with the transmission electron microscope. This could lead to better understanding of the pathogenesis of lesions and the means of treatment or prevention.


OBJECTIVE
To investigate the ultrastructure of acute laminitis as disease of greater severity is induced by increasing oligofructose (OF) dosage.


METHODS
Three pairs of normal horses, dosed with OF at 7.5, 10 and 12.5 g/kg bwt via nasogastric intubation, developed laminitis 48 h later. Following euthanasia, their forefeet were processed for transmission electron microscopy. Lamellar basal cell hemidesmosome (HD) numbers and the distance between the basal cell plasmalemma and the lamina densa of the basement membrane were estimated and compared to control tissue.


RESULTS
Increasing OF dosage caused greater HD loss and more severe laminitis. The characteristic separation of the basement membrane, cytoskeleton failure and rounded basal cell nuclei results from combined HD dysassembly and anchoring filament failure.


CONCLUSIONS
Without properly assembled HDs, dysadhesion between the lamina densa of the basement membrane (BM) and epidermal basal cells occurs, emphasising the fundamental importance of HDs in maintaining attachment at the lamellar interface. Medical conditions that trigger lamellar matrix metalloproteinase (MMP) activation and/or compromise entry of glucose into lamellar basal cells appear to promote loss and failure of HDs and, therefore, laminitis development.


CONCLUSIONS
A correlation between lameness severity and escalating loss of lamellar HDs now exists. Therapy aimed at protecting the lamellar environment from haematogenous delivery of MMP activators or from glucose deprivation may control laminitis development.
French
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Australian Equine Laminitis Research Unit, School of Veterinary Science, Faculty of Natural Resources Agriculture and Veterinary Science, The University of Queensland, Brisbane, Queensland 4072, Australia.
Pollitt
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CC
D000818:Animals; D001485:Basement Membrane / Q000166:cytology / Q000187:drug effects / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D005260:Female; D005534:Foot Diseases / Q000139:chemically induced / Q000473:pathology / Q000662:veterinary*; D022002:Hemidesmosomes / Q000187:drug effects / Q000648:ultrastructure*; D006724:Hoof and Claw / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure*; D006734:Horse Diseases / Q000139:chemically induced / Q000473:pathology*; D006736:Horses; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D046529:Microscopy, Electron, Transmission / Q000379:methods / Q000662:veterinary; D009844:Oligosaccharides / Q000009:adverse effects / Q000494:pharmacology*; D011897:Random Allocation; D012720:Severity of Illness Index
D009844:Oligosaccharides; C120489:oligofructose; D020778:Matrix Metalloproteinase 2