Regeneration of Peritoneal Mesothelium in a Rat Model of Peritoneal Fibrosis

BACKGROUND: Patients on long-term peritoneal dialysis develop progressive peritoneal fibrosis and loss of mesothelial layer. Regeneration of the mesothelium has been reported in the normal peritoneum but not the fibrotic peritoneum. Moreover, the origin of the regenerated mesothelial cells remains obscure. The aim of this study was to investigate mesothelial regeneration in fibrotic peritoneum induced by chlorhexidine gluconate. METHODS: Peritoneal fibrosis was induced by injection of CG into the peritoneal cavity of Wistar rats. After injection, the abdomen was opened, and the parietal fibrotic peritoneum with mesothelial cells was stripped from the abdominal wall, and then the abdominal incision was closed. Rats were sacrificed, and peritoneal tissues were dissected out at 0, 1, 3, 5, or 7 days after the stripping procedure. RESULTS: Spindle-shaped cells with microvilli appeared on the surface of stripped peritoneum at day 3 after denudation. Immunohistochemistry identified staining for vimentin, a marker of mesoderm cells, in the spindle-shaped cells at days 3, 5, and 7. Expression of alpha-SMA was observed in the same cells at days 3 and 5, but not 7. Expression of cytokeratin and HBME-1, markers for mesothelial cells, in these cells was delayed until day 7. CONCLUSIONS: Mesothelium can regenerate on the fibrotic peritoneum. The regenerated mesothelial cells seem to originate from vimentin-positive mesenchymal cells.