Structural reorganization of the cytoskeleton contributes to the induction of pro-fibrotic connective tissue growth factor in tubular epithelial cells

Abstract

Abstract. BACKGROUND:Tissue injuries and pathological changes are often associated with changes in cell adhesion and reorganization of cytoskeletal structures. This is of particular relevance for renal epithelial cells, which form a highly regulated barrier along the nephron. Here, we investigated the effect of the calcium chelator EGTA on morphological alterations and changes in pro-fibrotic gene expression in proximal renal tubular epithelial cells. METHODS: Epithelial cells were exposed to EGTA alone or in combination with TGF␤-1, followed by the analysis of N-cadherin and paxillin localization and cytoskeletal rearrangement. The expression of connective tissue growth factor (CTGF), a pro-fibrotic protein regulated by alterations of cell morphology, was investigated. RESULTS: Even low concentrations of EGTA, which did not lead to the loss of cell-cell interactions or cell detachment, were sufficient to reduce N-cadherin binding, to rearrange focal adhesion, to induce CTGF expression, and to strongly enhance TGF␤-1-mediated signaling. These data indicate a substantial crosstalk between the changes in cell cytoskeletal structures at the cell-cell adhesions and the signaling of soluble mediators. CONCLUSIONS: By linking cell-cell and cell-matrix interactions with the regulation of pro-fibrotic signaling, our studies provide deeper insights into the physiological mechanisms underlying the natural regeneration and repair processes in the kidney.