Equine laminitis: cleavage of laminin 5 associated with basement membrane dysadhesion.
BACKGROUND
The key lesion of laminitis is separation at the hoof lamellar dermal-epidermal interface. For this to happen the structural and adhesion proteins of the basement membrane zone must be altered. Which proteins and how damage to them leads to the lamellar separation of laminitis is unknown.


OBJECTIVE
To investigate lamellar hemidesmosome and cytoskeleton damage and basement membrane dysadhesion using light microscopy (LM) and immunofluorescence microscopy (IFM).


METHODS
Cryostat sections of lamellar tissues from 2 control and 6 Standardbred horses with oligofructose induced laminitis were studied using LM and IFM. Plectin, integrin alpha6 and BP230 antibody was used to label hemidesmosome intracellular plaque proteins and anti-BP180 and anti-laminin 5 (L5) was used to label anchoring filament (AF) proteins. Cytoskeleton intermediate filaments were labelled using anti-cytokeratin 14. The primary antibodies of selected sections were double labelled to show protein co-localisation.


RESULTS
Laminitis caused reduction of transmembrane integrin alpha6, the AF proteins BP180 and L5, and failure of co-localisation of BP180 and L5. Proteins of the inner hemidesmosomal plaque, plectin and BP230, were unaffected.


CONCLUSIONS
Loss of co-localisation of L5 and BP180 suggests that, during the acute phase of laminitis, L5 is cleaved and therefore, the AFs connecting the epidermis to the dermis, fail. Without a full complement of AFs separation at the lamellar dermo-epidermal junction occurs.


CONCLUSIONS
Suppressing or inhibiting metalloproteinase activity may prevent L5 cleavage and therefore the lamellar dermo-epidermal separation of laminitis.
French
K R
KR
Australian Equine Laminitis Research Unit, School of Veterinary Science, Faculty of Natural Resources Agriculture and Veterinary Science, The University of Queensland, Brisbane 4072, Australia.
Pollitt
C C
CC
D000208:Acute Disease; D000818:Animals; D000906:Antibodies / Q000276:immunology; D001485:Basement Membrane / Q000166:cytology / Q000473:pathology; D002448:Cell Adhesion / Q000502:physiology; D003599:Cytoskeleton / Q000473:pathology; D005534:Foot Diseases / Q000473:pathology / Q000662:veterinary*; D022002:Hemidesmosomes / Q000473:pathology; D006724:Hoof and Claw / Q000166:cytology / Q000473:pathology*; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses; D007150:Immunohistochemistry / Q000662:veterinary; D007249:Inflammation / Q000473:pathology / Q000662:veterinary; D007797:Laminin / Q000032:analysis / Q000502:physiology*; D008856:Microscopy, Fluorescence / Q000662:veterinary
D000906:Antibodies; D007797:Laminin