[Effect of TGF-beta1 stimulation on the smad signal transduction pathway of human peritoneal mesothelial cells].

OBJECTIVE: To explore whether the Smad signal transduction pathway in human peritoneal mesothelial cells (HPMCs) influences the process of human peritoneal fibrosis stimulated by TGF-beta1. METHODS: HPMCs were isolated from normal human omentum and 95% of the primary cultured cells was confirmed to be HPMCs. The third generation of cultured cells was stimulated by 5 ng/ml TGF-beta1. Immunohistochemistry, Western blotting, ELISA, and RT-PCR were employed to investigate the follows: the protein expression of p-Smad2/3 and its migration in HPMCs; the protein and mRNA expressions of SMAD 7 in cells; and the expressions of extracellular fibronectin (FN) protein, intracellular FN mRNA, as well as intracellular collenge-I (COL1) protein and mRNA. RESULTS: The protein expression of p-Smad2/3 in HPMCs obviously increased 15 min (29% p-Smad2/3-positive cells) after TGF-beta1 stimulation, peaking from 30 min (81% ) to 1 h (84%) and dropping after 2 h (37%); Meanwhile, p-Smad2/3 mainly distributed in cytoplasm at 15 min, concentrated in cell nucleus and peri-nucleus from 30 min to 1 h, and distributed in cytoplasm again at 2 h. The protein expression of SMAD7 in cells obviously increased 24 h after TGF-beta1 stimulation, peaking at 48 h. The mRNA expression of SMAD7 time-dependently increased. The expressions of extracellular FN protein, intracellular FN mRNA, as well as intracellular COL1 protein and mRNA significantly increased and all of them displayed time dependency. CONCLUSION: The SMAD signal transduction pathway of HPMCs can be specifically activated by TGF-beta1 and influence the process of human peritoneal fibrosis. With the stimulation of TGF-beta1, the protein and mRNA expressions of SMAD 7 (an inhibitor of SMAD pathway) significantly increase as a result of feedback.