Morphological and cellular changes in secondary epidermal laminae of horses with insulin-induced laminitis.
OBJECTIVE
To determine cellular changes associated with secondary epidermal laminae (SEL) in forefeet and hind feet of ponies with insulin-induced laminitis.


METHODS
8 ponies.


METHODS
Laminitis was induced in 4 ponies by IV administration of insulin and glucose; 4 control ponies received saline (0.9% NaCl) solution IV. Laminar tissue samples obtained from the dorsal aspects of the hooves were histologically evaluated. Primary epidermal lamina (PEL) length and width and SEL length, width, and angle were determined. Numbers of epidermal cell nuclei per micrometer and per total length of SEL and numbers of apoptotic and proliferative cells in axial, middle, and abaxial laminar regions were determined.


RESULTS
SEL in treatment group ponies were significantly longer, were significantly narrower, and had a smaller angle relative to PEL in all laminar regions versus control ponies. In treatment group ponies, the number of epidermal cell nuclei per SEL was typically higher and the number of cells per micrometer of SEL was lower in laminar regions, apoptotic cell numbers were higher in abaxial and middle regions in forefeet and hind feet, and proliferating cell numbers were higher in axial laminar regions in forefeet and all laminar regions in hind feet, versus control ponies.


CONCLUSIONS
Results indicated SEL elongation, narrowing, and alteration in orientation developed in all feet of ponies with insulin-induced laminitis. This was primarily attributable to cell stretching that developed at the same time as an accelerated cell death-proliferation cycle; differences in cell cycle responses among laminar regions between forefeet and hind feet may have been attributable to differences in load bearing.
Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, 00014 University of Helsinki, Finland.
Ninja P
NP
Karikoski
Janet C
JC
Patterson-Kane
Katie E
KE
Asplin
Thomas W
TW
McGowan
Megan
M
McNutt
Ellen R
ER
Singer
Catherine M
CM
McGowan
D000818:Animals; D005534:Foot Diseases / Q000139:chemically induced / Q000473:pathology / Q000662:veterinary*; D005947:Glucose / Q000633:toxicity; D006724:Hoof and Claw / Q000473:pathology*; D006734:Horse Diseases / Q000139:chemically induced* / Q000473:pathology; D006736:Horses; D007249:Inflammation / Q000139:chemically induced / Q000473:pathology / Q000662:veterinary; D007328:Insulin / Q000633:toxicity*
D007328:Insulin; D005947:Glucose