Role of connective tissue growth factor in the pathogenesis of diabetic nephropathy

Abstract

We characterized a rabbit polyclonal antibody raised against human recombinant connective tissue growth factor (CTGF). The antibody recognised a higher molecular mass form (approx. 56 kDa) of CTGF in mesangial cell lysates as well as the monomeric (36-38 kDa) and lower molecular mass forms (<30 kDa) reported previously. Immunohistochemistry detected CTGF protein in glomeruli of kidneys of non-obese diabetic mice 14 days after the onset of diabetes, and this was prominent by 70 days. CTGF protein is also present in glomeruli of human patients with diabetic nephropathy. No CTGF was detected in either normal murine or human glomeruli. Transient transfection of a transformed human mesangial cell line with a CTGF-V5 epitope fusion protein markedly increased fibronectin and plasminogen activator inhibitor-1 synthesis in cultures maintained in normal glucose (4 mM) conditions; a CTGF-antisense construct reduced the elevated synthesis of these proteins in high glucose (30 mM) cultures. Culture of primary human mesangial cells for 14 days in high glucose, or in low glucose supplemented with recombinant CTGF or transforming growth factor beta1, markedly increased CTGF mRNA levels and fibronectin synthesis. However, whilst co-culture with a CTGF-antisense oligonucleotide reduced the CTGF mRNA pool by greater than 90% in high glucose, it only partially reduced fibronectin mRNA levels and synthesis. A chick anti-CTGF neutralizing antibody had a similar effect on fibronectin synthesis. Thus both CTGF and CTGF-independent pathways mediate increased fibronectin synthesis in high glucose. Nevertheless CTGF expression in diabetic kidneys is likely to be a key event in the development of glomerulosclerosis by affecting both matrix synthesis and, potentially through plasminogen activator inhibitor-1, its turnover.

Connective Tissue Growth Factor Expressed in Tubular Epithelium Plays a Pivotal Role in Renal Fibrogenesis

“…Although others have reported similar findings such as COLI and FN in rat renal fibroblasts (8) and FN and PAI-1 in human mesangial cells (25), to our knowledge, this is the first report to show an increase in TIMP-1 mRNA levels in murine renal fibroblasts in response to CTGF treatment. rhTGF-␤1 (1.0 ng/ml) increased the mRNA levels of ␣1COLI and FN-EIIIA in TFB that were co-cultured with mProx24 to a significantly greater degree than in TFB that were cultured alone, suggesting the involvement of profibrotic humoral factors secreted by the mProx24.…”

“…Their findings, coupled with ours, support the notion that CTGF acts as an important profibrotic mediator of TGF-␤'s effects in the renal tubulointerstitium while not eliminating the possibility that it plays a similar role in the glomerulus. In fact, a number of studies have shown that mesangial CTGF expression plays a role in the pathogenesis of glomerulosclerosis, especially in diabetic nephropathy (5,6,11,25,36). Because intravenously injected antisense ODN is not appreciably absorbed by glomerular cells, it cannot significantly block their expression of the target genes (14,15).…”

Modulation of the Expression of Connective Tissue Growth Factor by Alterations of the Cytoskeleton

“…Hybridization was performed with cDNA probes labeled with [ 32 P]dCTP using the NonaPrimer kit from Appligene, Heidelberg, Germany. A cDNA specific for CTGF was kindly provided by N. Abdel-Wahab, London, UK (24). The blots were analyzed by phosphorimager or autoradiography.…”

Mastering a mediator: blockade of CCN-2 shows early promise in human diabetic kidney disease

“…CCN-2 bioactivity induces kidney fibroblast proliferation and ECM synthesis (Ito et al 1998), (Wahab et al 2001), (Twigg and Cooper 2004). Addition of recombinant CCN-2 to cultured mesangial cells increased the expression of ECM proteins including collagens and other matrix proteins present in DN (Murphy et al 1999).…”