11 Induction of vasculitic lesions in lupus-prone mice: A model for lupus-associated peripheral vascular disease

Background Systemic lupus erythematosus is an autoimmune disorder that affects many organs. Many patients develop vasculitis in skin and internal organs. There is no effective treatment for lupus-associated vasculitis. Research on the pathogenesis of lupus vasculitis has been hampered due to lack of appropriate model systems. Many patients with lupus develop chronic changes in skin, kidney and other organs, characterized by fibrosis. To understand the induction and mechanisms of fibrosis in lupus, we injected lupus-prone mice with bleomycin that is known to induce fibrotic disease in otherwise normal C57/Bl6 mice, and monitored the animals for disease phenotype. Methods We injected MRL-MpJ-Fas lpr/lpr (MRL-lpr) mice with bleomycin (100 µg, subcutaneously on upper back) or PBS daily for 14 days. Following which, animals were monitored daily for 14 days. Photographs were taken for skin lesions. On day 28, skin, paws, lung, liver, and kidneys were harvested and tissues sectioned for H and E and Masson Trichrome staining. Immunohistochemistry was performed to detect blood vessels and endothelial cells, namely -smooth muscle actin (SMA) and CD31, respectively. Experiments were repeated in MRL-MpJ-Fas +/+ (MRL+/+) mice. Results Around day 10 of injections, the tips of front and hind paw digits of 7 of 10 bleomycin-injected MRL-lpr and 3 of 3 bleomycin-injected MRL+/+mice developed erythematous lesions that ulcerated. None of the controls (5 PBS-injected MRL-lpr, 3 PBS-injected MRL+/+, and 3 bleomycin-injected C57/Bl6 mice) developed such lesions. Such lesions have also not been observed in over 50 unmanipulated MRL-lpr and MRL+/+mice or over 30 bleomycin-injected C57/Bl6 mice in our animal colony in previous studies. Histological and immunohistochemistry analyses showed increased infiltration, fibrosis, tissue destruction, and CD31 expression in bleomycin-injected MRL-lpr mice as compared to control animals. Massons trichrome staining revealed significantly increased dermal fibrosis in bleomycin-injected MRL-lpr mice as compared to PBS-injected MRL-lpr mice. Preliminary analysis shows increased alveolar hemorrhage in bleomycin-injected MRL-lpr mice as compared to control mice. Conclusions The vasculitic lesions that we observed in the digits of bleomycin-injected MRL-lpr and MRL+/+mice mimics vasculitic lesions seen in patients with lupus. Thus, bleomycin injection in lupus-prone mice can serve as a model for chronic vascular changes seen in lupus and other systemic rheumatic diseases. Funding Source(s): None