Assessment of apoptosis in epidermal lamellar cells in clinically normal horses and those with laminitis.
OBJECTIVE
To determine and compare the number, type, location, and distribution of apoptotic epidermal cells in the laminae of clinically normal horses and horses with laminitis.


METHODS
Formalin-fixed samples of digital lamellar tissue from 47 horses (including clinically normal horses [controls; n = 7], horses with acute [4] and chronic [7] naturally acquired laminitis, and horses with black walnut extract-induced [11] or carbohydrate overload-induced [18] laminitis).


METHODS
Blocks of paraffin-embedded lamellar tissues were stained for DNA fragmentation with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) technique. Differential immunohistochemical staining for caspases 3 and 14 were used to confirm apoptosis.


RESULTS
The number of TUNEL-positive epidermal cells per 0.1 mm of primary laminae was significantly greater in the acute laminitis group than in the other groups. In the acute laminitis group, there were 17 and 1,025 times as many TUNEL-positive basal layer cells and keratinocytes, respectively, compared with the control group. Apoptosis of TUNEL-positive basal layer cells was confirmed by results of caspase 3 immunohistochemical staining. The TUNEL-positive keratinocytes did not stain for caspases 3 or 14.


CONCLUSIONS
The large number of apoptotic basal layer cells detected in the lamellar tissue of horses with acute naturally acquired laminitis suggests that apoptosis may be important in the development of acute laminitis. The role of the large number of TUNEL-positive keratinocytes detected in the interface of primary and secondary epidermal laminae of horses with acute laminitis remains to be elucidated.
Faleiros
Rafael R
RR
Post-Graduate Program of Veterinary Surgery, Faculdade de Ciências Agrárias e Veterinárias da Universidade Estadual Paulista, Jaboticabal, SP, Brazil.
Stokes
Ashley M
AM
Eades
Susan C
SC
Kim
Dae Young
DY
Paulsen
Daniel B
DB
Moore
Rustin M
RM
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053456:Caspase 14; D053148:Caspase 3; D020169:Caspases; D004249:DNA Damage / Q000502:physiology*; D004817:Epidermis / Q000473:pathology*; D006734:Horse Diseases / Q000503:physiopathology*; D006736:Horses; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D012871:Skin Diseases / Q000503:physiopathology / Q000662:veterinary*
D053456:Caspase 14; D053148:Caspase 3; D020169:Caspases