Abstract: Objective  To investigate the role and mechanism of high calcium ion concentration in regulating epithelial-mesenchymal transition (EMT) of human peritoneal mesothelial cells through the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway.  Methods  Human peritoneal mesothelial cells HMrSV5 were cultured and divided into the following groups: control group (Ca2+ 1.25 mmol/L), 1.75 mmol/L Ca2+ group, 2.25 mmol/L Ca2+ group, solvent control group (Ca2+ 1.25 mmol/L, 0.1% dimethyl sulfoxide), 2.25 mmol/L Ca2+ + solvent group (Ca2+ 2.25 mmol/L, 0.1% dimethyl sulfoxide), 2.25 mmol/L Ca2+ + S3I-201 (STAT3 inhibitor) group (Ca2+ 2.25 mmol/L, S3I-201 100 μmol/L), and 2.25 mmol/L Ca2+ + Stattic (STAT3 inhibitor) group (Ca2+ 2.25 mmol/L, Stattic 1.5 μmol/L). After 48 hours of treatment, number of invasive cells, mRNA and protein expression levels of α-smooth muscle actin (α-SMA) and E-cadherin, and phosphorylation levels of JAK1, JAK2, STAT3 and STAT6 were measured.  Results  In 1.75 mmol/L Ca2+ group and 2.25 mmol/L Ca2+ group, number of invasive cells (t=6.901 and 10.870, P＜0.001), α-SMA mRNA (t=5.375 and 9.564, P＜0.001), α-SMA protein (t=7.018 and 10.859, P＜0.001), phosphorylation of JAK2 (t=7.031 and 11.001, P＜0.001) and phosphorylation of STAT3 (t=5.425 and 9.846, P=0.001 and ＜0.001) were significantly higher than those in control group; E-cadherin mRNA (t=4.457 and 10.749, P=0.002 and ＜0.001) and E-cadherin protein (t=6.519 and 11.351, P＜0.001) were lower than those in control group; while phosphorylation levels of JAK1 and STAT6 (F=0.423 and 0.311, P=0.619 and 0.674) had no differences as compared with those of control group. In 2.25 mmol/L Ca2+ + S3I-201 group and 2.25 mmol/L Ca2++ Stattic group, number of invasive cells (t=7.259 and 6.995, P＜0.001), α-SMA mRNA (t=5.230 and 5.851, P=0.001 and ＜0.001),  α-SMA protein (t=7.684 and 7.833, P＜0.001), and phosphorylation of STAT3 (t=6.753 and 8.574, P＜0.001) were lower than those of 2.25 mmol/L Ca2+ + solvent group; E-cadherin mRNA (t=7.500 and 8.173, P＜0.001) and E-cadherin protein (t=13.021 and 9.340, P＜0.001) were higher than those of 2.25 mmol/L Ca2+ + solvent group; while phosphorylation of JAK2 (t=0.754 and 1.091, P=0.473 and 0.307) had no difference as compared with that of 2.25 mmol/L Ca2+ + solvent group.  Conclusion  High Ca2+ concentration activates the signaling pathway via phosphorylation of STAT3 to promote EMT of human peritoneal mesothelial cells.

Key words: Peritoneal fibrosis, Peritoneal mesothelial cells, Janus kinase 2, Signal transducer and activator of transcription 3, Epithelial-mesenchymal transition