Objective: To investigate the expression and the potential role of TGF-beta/Smads in peritoneal fibrosis induced by high glucose dialysate and LPS in rats.
Methods: 24 male Sprague-Dawley rats were randomly allocated into four groups: control group, normal rats; LPS group: rats were treated with intraperitoneal injection of LPS (0.6 mg/kg body weight) on days 1, 3, 5, 7; dialysate Group: rats were treated with daily intraperitoneal injection of 4.25% peritoneal dialysate (100 ml/kg body weight) for 4 weeks; LPS + dialysate Group: daily intraperitoneal injection of 4.25% dialysate combined with four times injection of LPS (0.6 mg/kg body weight on days 1, 3, 5, 7) for 4 weeks. The parietal thickness was measured with masson stain. The expression of alpha-SMA, TGF-beta1, Smad 2/3, Smad 7 and ColI in peritoneal membrane was detected with confocal microscope by immuno-fluorescence, Western-blot and RT-PCR.
Results: Masson stain show the parietal thickness of the rats in all groups was significantly increased compared with control group and collagen deposition was evident in the thickened submesothelial compact zone. Parietal thickness of the rats in LPS + dialysate Group was most (vs LPS group: 41.5 +/- 3.3 microm vs 34.70 +/- 3.6 microm, P = 0.007, vs dialysate Group, 41.5 +/- 3.3 microm vs 20.2 +/- 3.6 microm, P = 0.000). The expression of alpha-SMA, Col I, TGF-beta1, Smad 3 was up-regulated in protein and mRNA level and the protein level of phosphorylated-Smad 2/3 was increased significantly. The most significant changes were found in LPS + dialysate Group. Compared with control group the mRNA and protein level of Smad7 was increased, but the protein ratio of phosphorylated Smad/Smad 7 in all groups was higher. Under electro-microscope, the mesothelial cells in LPS + dialysate Group had myofibroblast morphology with the presence of large bundles of actin microfilaments and dense bodies within the cytoplasm.
Conclusions: High concentration glucose dialysate or LPS contributes to peritoneal fibrosis by stimulating TGF-beta/Smads signaling. 4.25% peritoneal dialysate can coordinate with LPS to activate TGF-beta/Smads signaling pathway and induce mesenchymal transdifferentiation and peritoneal fibrosis.