Persistent transforming growth factor-beta 1 expression may predict peritoneal fibrosis in CAPD patients with frequent peritonitis occurrence

The efficiency of continuous ambulatory peritoneal dialysis depends on the permeability of the peritoneal membrane. Peritoneal fibrosis (PF) causes lo ss of the dialytic function. Several studies have indicated that PF is clos ely related to the proliferation of peritoneal fibroblasts and the depositi on of extracellular matrix. Transforming growth factor-beta 1 (TGF-beta 1) plays a major role in stimulating extracellular matrix deposition. Frequent peritonitis occurrence may cause persistent TGF-beta 1 mRNA expression. In an attempt to search for a factor related to PF, we designed a longitudina l study to measure TGF-beta 1 levels in dialysate and TGF-beta 1 mRNA expre ssion in peritoneal mononuclear cells from peritoneal dialysate before onse t, once a week during peritonitis, and after peritonitis in high and low pe ritonitis occurrence (HPO and LPO) patients. Fifteen patients with a LPO ra te and 5 patients with a HPO rate were followed up longitudinally. Meanwhil e, TGF-beta 1 levels and TGF-beta 1 mRNA expression were augmented in perit oneal dialysate effluents before, during, and after the episodes of periton itis. The peritoneal permeability was evaluated by the peritoneal equilibra tion test. The results revealed that in the LPO group, TGF-beta 1 and TGF-b eta 1 mRNA were detectable at early stages of peritonitis, but the levels d ecreased rapidly and were undetectable 2 weeks after peritonitis. On the ot her hand, in the HPO group, TGF-beta 1 and TGF-beta 1 mRNA persisted for a long time. We could detect TGF-beta 1 and TGF-beta 1 mRNA in dialysate effl uents and peritoneal mononuclear cells even 2, 3, and 4 weeks after episode s of peritonitis. When compared with that of first or second episode of per itonitis, the peritoneal function evaluated with the peritoneal equilibrati on test was found to obviously deteriorate during the third episode of peri tonitis. These findings were confirmed by an in situ hybridization techniqu e to evaluate the relationship between TGF-beta 1 mRNA expression and PF fr om biopsied peritoneal specimens. These findings suggest that the high TGF- beta 1 levels in the dialysate are related to an increased expression of TG F-beta 1 in the peritoneum. Thus, the persistent TGF-beta 1 expression in t he peritoneum may serve as a useful parameter in predicting PF in continuou s ambulatory peritoneal dialysis patients with frequent peritonitis occurre nce.