Figure 1.

PM schemas and biopsies representing the normal peritoneal structure and its changes during PD. Possible therapeutic approaches. (a) and (b) are adapted with permission from Aguilera et al. (2013). Available from http://www.intechopen.com/books/the-latest-in-peritoneal-dialysis/the-mesothelial-to-mesenchymal-transition-a-pathogenic-and-therapeutic-key-for-peritoneal-membrane-f [80]. (a) Realistic representation of a healthy peritoneal cavity. A preservation of the mesothelial layer is clearly seen, only a few fibroblasts and vessels are visible, and only a small layer of extracellular matrix lies in the compact zone of the muscle layer. (b) After exposure to PD liquids, the structure of the PM starts to change dramatically with the appearance of more fibroblasts, macrophages, and inflammatory cytokines and finally with deposition of more extracellular matrix (ECM) cells. Inflammation and fibrosis will be the result of these changes. Some drugs like COX-2 inhibitors, PPRAγ agonists, or RAS targeting are possible therapeutic strategies to protect from PD complications such as inflammation, angiogenesis, fibrosis, and/or MMT. (c) A peritoneal biopsy of a mouse peritoneal membrane that was treated with physiological saline is shown as control. The PM is well preserved and fibrotic response is absent. (d) Peritoneal biopsy of a mouse PM that was exposed to PDF for 40 days. A significant fibrotic response can be observed with a larger ECM and many inflammatory cells.