Scleroderma or systemic sclerosis (SSc) is a disorder of the connective tissues affecting various organsystems. The disease is complex and is characterized by excessive accumulation of collagen and otherextracellular matrix components in the skin and internal organs. Because increased signaling by TGF-beta hasbeen implicated in this disease we recently established a novel mouse model in which the TGF-beta Receptor1is constitutively activated in fibroblasts post-natally (TBR1CA; Col1a2-CreER). These mice recapitulated themajor features of human SSc, showing pronounced and generalized fibrosis of the dermis, thinner epidermis,loss of hair follicles, and fibrotic thickening of small blood vessel walls in lung and kidney. Primary skinfibroblasts of these mice showed elevated expression of downstream TGF-beta targets, reproducing thehallmark biochemical phenotype of explanted SSc dermal fibroblasts. In particular there was a markedincrease in connective tissue growth factor (CTGF) expression. Since increased expression of CTGF hasbeen implicated to play a key role in the disease process, we generated transgenic mice that over-expressCTGF in fibroblasts (Col1a2-CTGF) by using a fibroblast-specific promoter/enhancer from the pro-D2(l)collagen gene. The animals exhibit a severe loss of hair. Initial histological examination of skin biopsiesshowed pronounced and generalized fibrosis of the dermis, thicker epidermis and inflammatory infiltrates inthe area of the skin fibrosis. Preliminary analysis of mouse embryonic fibroblasts derived from thesetransgenic mice showed elevated expression of collagen type I and Timp-3.We propose to characterize the Col1a2-CTGF mice as well as their explanted skin fibroblasts. Tounderstand the mechanisms by which increased expression of CTGF in fibroblasts causes a fibrotic disease,we will also perform a comparison of the molecular phenotypes of the skin fibroblasts of these mice withthose of TBR1CA; Col1a2-CreER mice and with those of specific human scleroderma patients. To furtherexamine these mechanisms we propose to attenuate the fibrotic phenotypes of the skin fibroblasts of the twotransgenic mouse models of scleroderma by pharmacological inhibitors of specific signaling pathways orsiRNAs. We also will attempt to inhibit the fibrotic phenotypes of these transgenic mice in vivo by crossingnull mutations in either SmadS or integrin D6 in these mice. Finally, we will examine the mechanisms thatcause increased sensitivity to bleomycin-induced lung fibrosis in TBR1CA; Col1a2-CreER mice and testwhether a similar sensitivity occurs in Col1a2-CTGF mice. These studies should give information about therelative importance of TGF-beta and CTGF in causing fibrotic diseases.
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