CTGF Mediates TGF-β–Induced Fibronectin Matrix Deposition by Upregulating Active α5β1 Integrin in Human Mesangial Cells

[摘要] ABSTRACT. Excessive deposition of fibronectin in the glomerular mesangium in diabetic nephropathy (DN) is partly due to the induction of transforming growth factor-β (TGF-β) by high glucose. TGF-β induces its downstream mediator connective tissue growth factor (CTGF), which stimulates fibronectin matrix synthesis, a process that requires the presence of α5β1 integrin. Although TGF-β has been shown to upregulate α5β1 integrin expression in human mesangial cells (HMC), little is known about the effect of CTGF on levels of this receptor. This study tested whether CTGF modulates α5β1 expression by HMC in culture and whether changes induced by TGF-β are mediated through the induction of CTGF. FACS analysis showed that both TGF-β and CTGF significantly increased cell-surface α5β1 levels compared with basal conditions. RT-PCR indicated that the changes were at the level of transcription. Treatment of cells with TGF-β and antisense CTGF oligonucleotides significantly reduced the TGF-β–induced increases in α5β1 levels. CTGF and TGF-β also significantly increased levels of ligand-occupied cell-surface β1 integrins and cell adhesion to fibronectin, the main α5β1 substrate. Antisense CTGF significantly reduced the number of adherent cells from TGF-β–stimulated cultures. Finally, α5β1 blocking antibodies inhibited HMC fibronectin matrix deposition, confirming the importance of this receptor for this process. Taken together, these data provide evidence that CTGF controls α5β1 expression by HMC in vitro. Alterations in α5β1 levels induced by TGF-β are mediated at least in part through the induction of CTGF, and specific targeting of either α5β1 or CTGF could be useful in controlling excessive fibronectin matrix production in DN. E-mail [e-mail]

[学科分类] 泌尿医学

[关键词] Bone marrow necrosis;Sickle cell disease;Hyperhemolysis syndrome