This study reconstructs the whole sequence of mesothelial injury and regeneration in patients on longterm peritoneal dialysis. Our observations indicate that peritoneal dialysis induces a process of continuous mesothelial injury and regeneration. New mesothelial cells seem to originate from wandering mesothelial cells of the peritoneal fluid, as well as from mesothelial cell precursors localized in the sub-mesothelial connective tissue.

The peritoneum has been classically considered to be an inert passive membrane. Previous studies demonstrated the presence of fixed anionic charges at the level of the peritoneal microvasculature and the subserosal interstitium. The present study describes the selective distribution of fixed anionic charges in the mesothelial cell plasmalemma and organelles as well as in the submesothelial basal lamina of rat and mice visceral, parietal and diaphragmatic peritoneum. These data support the idea that the peritoneum should be considered a negatively charged biological dialyzing membrane with selective capabilities. Therefore, transperitoneal transfer of charged solutes cannot be analyzed just on the basis of their molecular weight, size and shape.