Role of TGF-beta and CTGF Signaling Transgenic Mouse Models of Scleroderma

University Of Texas Hlth Sci Ctr Houston, Houston TX

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Abstract

Scleroderma or systemic sclerosis (SSc) is a disorder of the connective tissues affecting various organ[unreadable] systems. The disease is complex and is characterized by excessive accumulation of collagen and other[unreadable] extracellular matrix components in the skin and internal organs. Because increased signaling by TGF-beta has[unreadable] been implicated in this disease we recently established a novel mouse model in which the TGF-beta Receptor1[unreadable] is constitutively activated in fibroblasts post-natally (TBR1CA; Col1a2-CreER). These mice recapitulated the[unreadable] major features of human SSc, showing pronounced and generalized fibrosis of the dermis, thinner epidermis,[unreadable] loss of hair follicles, and fibrotic thickening of small blood vessel walls in lung and kidney. Primary skin[unreadable] fibroblasts of these mice showed elevated expression of downstream TGF-beta targets, reproducing the[unreadable] hallmark biochemical phenotype of explanted SSc dermal fibroblasts. In particular there was a marked[unreadable] increase in connective tissue growth factor (CTGF) expression. Since increased expression of CTGF has[unreadable] been implicated to play a key role in the disease process, we generated transgenic mice that over-express[unreadable] CTGF in fibroblasts (Col1a2-CTGF) by using a fibroblast-specific promoter/enhancer from the pro-D2(l)[unreadable] collagen gene. The animals exhibit a severe loss of hair. Initial histological examination of skin biopsies[unreadable] showed pronounced and generalized fibrosis of the dermis, thicker epidermis and inflammatory infiltrates in[unreadable] the area of the skin fibrosis. Preliminary analysis of mouse embryonic fibroblasts derived from these[unreadable] transgenic mice showed elevated expression of collagen type I and Timp-3.[unreadable] We propose to characterize the Col1a2-CTGF mice as well as their explanted skin fibroblasts. To[unreadable] understand the mechanisms by which increased expression of CTGF in fibroblasts causes a fibrotic disease,[unreadable] we will also perform a comparison of the molecular phenotypes of the skin fibroblasts of these mice with[unreadable] those of TBR1CA; Col1a2-CreER mice and with those of specific human scleroderma patients. To further[unreadable] examine these mechanisms we propose to attenuate the fibrotic phenotypes of the skin fibroblasts of the two[unreadable] transgenic mouse models of scleroderma by pharmacological inhibitors of specific signaling pathways or[unreadable] siRNAs. We also will attempt to inhibit the fibrotic phenotypes of these transgenic mice in vivo by crossing[unreadable] null mutations in either SmadS or integrin D6 in these mice. Finally, we will examine the mechanisms that[unreadable] cause increased sensitivity to bleomycin-induced lung fibrosis in TBR1CA; Col1a2-CreER mice and test[unreadable] whether a similar sensitivity occurs in Col1a2-CTGF mice. These studies should give information about the[unreadable] relative importance of TGF-beta and CTGF in causing fibrotic diseases.