Animal model of sclerotic skin. III: Histopathological comparison of bleomycin-induced scleroderma in various mice strains.

We have recently established a mouse model for scleroderma by repeated local bleomycin treatment. In this study, we compared the susceptibility to bleomycin in the development of dermal sclerosis among Balb/c, C3H/He, C57BL/6J, A/J, DBA/2, B10.BR, B10.A, and B10.D2 mouse strains. After either bleomycin or PBS treatment, skin from the injection site was histologically examined. Dermal sclerosis was induced by bleomycin treatment for 4 weeks in all of the strains examined. In particular, C3H/He, DBA/2, B10.D2 and B10.A mice developed intense dermal sclerosis characterized by deposition of homogeneous material in the dermis and thickened collagen bundles. Dermal thickness showed a more than twofold increase following bleomycin treatment, as compared with PBS treatment, except in C57BL/6J and DBA/2 mice. In A/J, C3H/He, B10.A, and B10.D2 mice, dermal thickness showed a more than 2.5-fold increase. Mast cell numbers in sclerotic skin were significantly greater than in PBS-treated skin in Balb/c and B10.A mice after 4 weeks of treatment. We also examined whether bleomycin treatment for 3 weeks could induce dermal sclerosis in C3H mice. Histological examination revealed that epidermal thickness as well as dermal sclerosis was increased in C3H mice following bleomycin treatment for 3 weeks. Increased hydroxyproline content as well as mRNA expression of alpha1(I) collagen, as determined by Northern blot analysis, were observed following bleomycin treatment. Taken together, we conclude that C3H/He and B10.A mouse strains are bleomycin-'susceptible', and these strains are considered to be a suitable experimental model of bleomycin-induced scleroderma.