Skin-induced sclerosis after bleomycin treatment. Because of their inherent fragility, nude mice were injected subcutaneously with 30 mg bleomycin (BLM)/site daily during 1 month (both flanks and neck). Mice injected with 0.9% sodium chloride (NaCl) saline solution presented the same characteristics as untreated mice; only the control mice are represented. (a) Healthy skin (hematoxylin and eosin). (b) Fibrotic skin changes observed after BLM treatment. Macroscopically, injection sites appeared thicker and indurated to the touch (macroscopic picture, red ellipses). Histological analyses of BLM injection sites showed a global increase in skin thickness, and a decrease in the amount of subcutaneous fat tissue (histological picture). Comparison of (c) the dermis, (d) the epidermis and (e) the total skin thickness at the end of the BLM treatment (5 weeks). Data presented as mean ± standard deviation (**P <0.01, control mice n = 6, BLM-treated mice n = 6). (f) Time course of body weight (grams) (**P <0.01, control mice + NaCl-treated mice n = 24, BLM-treated mice n = 48). A break in the growth curve was observed at the end of BLM treatment (fifth week) and during all of the experiment (13th week). Bars = 250 μm. White, BLM-untreated mice; black, BLM-treated mice.