Chronic proliferative
dermatitis (cpd) is a spontaneous mutation in C57BL/Ka mice (cpdm/cpdm). The
dermatitis is characterized by redness, hairloss, scaling,
pruritus and histologically by epithelial hyperproliferation, infiltration of eosinophils, macrophages and mast cells. Lesions similar to those in the skin occur in the esophagus and forestomach. In this paper, we describe the effect of
drug treatments directed against epidermal hyperproliferation (
calcipotriene and
etretinate), against
inflammation (
corticosteroids and
dapsone) and against
pruritus (loratidine and
capsaicin). The criteria used to objectively estimate the effect of the treatment were 1) macroscopic evaluation of the lesions (cpd score), 2) degree of epithelial hyperproliferation assessed by
BrdU incorporation and epithelial thickness, and 3) microscopic evaluation of the inflammatory cells in the skin samples. Treatment of the cpdm/cpdm mice with
calcipotriene (5 microg/day for 3 weeks) inhibited epidermal proliferation and the number of eosinophils. Systemic
etretinate treatment (30 microg/g/day for 3 weeks) was not very effective. Topical
corticosteroids (0.05 microg/day, for 3 weeks) exerted a
therapeutic effect on the hyperproliferation and the number of eosinophils. Oral
dapsone treatment (34 microg/g/day, for 5 weeks) reduced the
BrdU incorporation in the skin and the epithelial thickness in the esophagus. The anti-
histamine loratidine (orally, 1.7 microg/ g/day, for 4 weeks) reduced the severity of the lesions macroscopically, probably by suppressing the
pruritus.
Capsaicin (topically, 30 mM, for 5 weeks) also reduced the severity of the macroscopic observable lesions. Moreover,
capsaicin reduced the dorsal and ventral epidermal thickness. The results from this and previous studies indicate that
steroids (topically and systemically) and less strongly
calcipotriene are the most effective treatments for the lesions observed in the cpdm/cpdm mice, since both hyperproliferation and the influx of eosinophils are reduced. Although the pathogenesis of the cpd lesions remains to be determined, our results indicate that the cpdm/cpdm mouse can be used to investigate new drugs for their possible application in chronic
dermatitis.