TGFB1 and fibrosis: Together, these data provide both gain- and loss-of-function evidence that CTGF plays a crucial role in fibrotic tissue injury, because exogenous CTGF was required to initiate a fibrotic response in the presence of increased TGF-β levels, and because treatment with a CTGF-blocking antibody attenuated the fibrotic response in three independent models of pathologic fibrosis.