Adenoviral Gene Transfer of Connective Tissue Growth Factor in the Lung Induces Transient Fibrosis

Abstract

Connective tissue growth factor (CTGF) is felt to be one of the key profibrotic factors and is a downstream effector molecule mediating the action of transforming growth factor (TGF)-beta1, a cytokine known to induce severe and progressive fibrosis. However, the in vivo fibrogenic effect of isolated CTGF expression is not well described. We used adenoviral gene transfer to transiently overexpress CTGF in rat lungs after intratracheal administration and compared it with transient overexpression of active TGF-beta1 delivered by a similar adenovirus vector. This high expression of CTGF over 6-10 days induced a moderate but reversible fibrosis. We observed an increase of fibronectin, procollagen 1a2, and endogenous CTGF gene expression at 14 days, which suggested an indirect activation by CTGF. Tissue inhibitor of metalloproteinase-1 was weakly and transiently upregulated after CTGF exposure. These same genes were robustly and persistently stimulated by TGF-beta1 from Day 3 to Day 21. This data suggested that CTGF may act as a TGF-beta1 cofactor rather than a direct fibrogenic factor. We demonstrate that CTGF overexpression can initiate fibrogenic activity but likely requires the presence of additional factors, such as tissue inhibitor of metalloproteinase-1, to maintain a nonfibrolytic environment and to cause progression of fibrosis.

Pivotal role of connective tissue growth factor in lung fibrosis: MAPK‐dependent transcriptional activation of type I collagen

“…Moreover, mice treated with the anti-CTGF antibody after bleomycin challenge displayed improved lung tissue architecture and reduced expression of type I collagen and ␣-SMA. Thus, these data are consistent with recent findings showing that, whereas CTGF overexpression is, on its own, insufficient for causing lung fibrosis in vivo, CTGF expression produces a susceptibility to lung fibrosis and enhances the fibrotic response (32,33). The findings from a very recent report, in which application of the anti-CTGF antibody reduced TGF␤-induced skin fibrosis in mice (34), also support our findings and strengthen the notion of a direct role for CTGF in fibrosis enhancement and progression.…”

“…First, in a bleomycin-resistant mouse model (BALB/c), CTGF was not up-regulated in response to challenge with bleomycin (6). Moreover, Bonniaud and colleagues further demonstrated that adenovirus-based delivery of CTGF to a bleomycin-sensitive mouse strain (C57BL/6) caused a transient fibrotic response (32), but in the resistant BALB/c strain, the lung was rendered susceptible to bleomycin-induced fibrosis (33).…”

The C-terminal module IV of connective tissue growth factor is a novel immune modulator of the Th17 response

“…60 CCN2 overexpression in rat lungs only caused a temporal induction of procollagen gene expression and transient matrix accumulation, but it is not sufficient to induce progressive fibrosis. 61 Podocyte-specific CCN2-transgenic mice (in C57BL/6 background) exhibited no glomerular abnormalities, proteinuria, or matrix accumulation, although they were more susceptible to streptozotocin-induced diabetes. 62 Our in vivo data showed a similar response in the kidney.…”

TGF-β1 Induces Progressive Pleural Scarring and Subpleural Fibrosis

“…TGF-␤1 has been widely studied in the context of fibrotic diseases. This growth factor is known for its anti-inflammatory effects, is chemotactic for fibroblasts and promotes the accumulation of extracellular matrix (27). Transient overexpression of active TGF-␤1 in rat lungs by adenoviral gene transfer causes progressive lung fibrosis without major inflammation, characterized by extensive deposition of extracellular matrix proteins such as collagen and fibronectin and by accumulation of myofibroblasts (20).…”