BACKGROUND: Epithelial-mesenchymal transition (EMT) is important in the development of peritoneal fibrosis. Glucose degradation products (GDPs) may induce EMT in human peritoneal mesothelial cells (HPMCs). METHODS: The effects of individual GDPs and GDPs derived from peritoneal dialysis fluid (PDF) in both HPMCs and peritoneal membranes were evaluated. EMT was assessed with alpha-smooth muscle actin (alpha-SMA) and E-cadherin. RESULTS: In vitro, alpha-SMA protein and mRNA levels increased in the presence of the GDPs (formaldehyde, glyoxal, methylglyoxal, and 3-deoxyglucosone), and E-cadherin decreased. Changes in the EMT markers were most prominent after exposure to 3-deoxyglucosone. Changes in both alpha-SMA and E-cadherin protein levels were less with low (L)-GDP bicarbonate/lactate-buffered PDF compared to high (H)-GDP PDF. In the rat model after 8 weeks' PDF infusion, the alpha-SMA/E-cadherin mRNA ratio increased in the H-GDP group compared with the L-GDP group (p < 0.05). The peritoneum in the H-GDP group tended to be thicker (p = 0.052) and had more blood vessels than that in the L-GDP group (p < 0.05). Tissue staining for TGF-beta1 decreased in the L-GDP group. Dual-stained cytokeratin and alpha-SMA-positive myofibroblasts in the submesothelial layer were more prominent in the H-GDP group. CONCLUSION: GDPs found in PDF induce EMT of HPMCs, which is associated with peritoneal fibrosis and vascularization. Conversely, L-GDP PDF reduces EMT and peritoneal fibrosis.
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