Role of Wnt signaling pathway on the epithelial to mesenchymal transition induced by parathyroid hormone in renal tubular epithelial cells

Abstract

Objective To observe the effect of parathyroid hormone on transdifferentiation of human renal proximal tubular epithelial cell (HK-2), and to investigate the role of Wnt signaling pathway in this process. Methods The expression of α-SMA, E-cadherin mRNA and protein was detected by real-time PCR and Western blotting. After the induction of 10-10 mol/L PTH for 48 h, the Wnt pathway associated gene expression profiling was detected by quantitative PCR-microarray. The expression of Wnt4 mRNA and protein under various concentrations of PTH or after exposed to 10-10 mol/L PTH for different time was detected by real-time PCR and Western blotting. The overexpression and knock-down plasmids of Wnt4 were constructed and the expression of α-SMA, E-cadherin, Wnt4 mRNA and protein was detected by real-time PCR and western blotting after overexpression and knockdown of Wnt4. Results Compared with PTH group, the expression of α-SMA mRNA and protein in PTH+DKK1 group was significantly down-regulated, while E-cadherin mRNA and protein expression was significantly up-regulated (all P <0.01). PTH treatment resulted in the up-regulation of 18 genes and down-regulation of 9 genes associated with Wnt pathway. Compared with control group, the expression of Wnt4 mRNA and protein increased markedly in PTH group (all P <0.01). The expression of α-SMA mRNA and protein was significantly up-regulated and E-cadherin mRNA and protein expression was significantly down-regulated after overexpression of Wnt4 and PTH treatment (all P <0.05), while the expression of α-SMA mRNA and protein was significantly down-regulted and E-cadherin mRNA and protein expression was significantly down-regulated after knockdown of Wnt4 and PTH treatment (all P <0.05). Conclusions PTH-induced EMT in HK-2 cells is mediated by Wnt signal pathway, and Wnt4 might be a key gene during PTH-induced EMT. Key words: Parathyroid hormone; Transdifferentiation, cell; Signal pathways