Angiogenesis and Lymphangiogenesis in Peritoneal Dialysis

The ultrafiltration failure during peritoneal dialysis (PD) is related to inflammatory responses induced by bio-incompatible PD fluids, which may lead to deterioration of peritoneal membrane (PM) function. Mesothelial cells, lymphocytes, macrophages and other cell types present in the peritoneal cavity are stimulated to produce cytokines and growth factors that promote pathological processes. Due to these factors, blood and lymphatic vessels proliferate and could be responsible for hyperfiltration and PM failure type III and IV. Vessels proliferation may be related to fibrosis, being the cause and/or effect of the mesenchymal conversion of different cell types such as mesothelial (MMT), bone marrow-derived (fibrocytes) or endothelial (vascular- and lymph-endo-MT) cells. Lymphangiogenesis in PD is a poorly analysed process; however, its contribution to peritoneal function disorders has been recently recognized. VEGF production is associated with blood and lymphatic vessels proliferation, while specifically lymphangiogenesis is mainly regulated by VEGF-C and VEGF-D. Excessive lymphatic fluid drainage from the abdominal cavity may be related with macromolecule and isosmotic solutions reuptake and convective reabsorption of solutes that were cleared from plasma by diffusion. Some drugs have been shown to modulate tissue fibrosis, MMT, EndoMT, angiogenesis and lymphangiogenesis and could represent interesting therapeutic strategies to protect the PM

T Helper 17/Regulatory T Cell Balance and Experimental Models of Peritoneal Dialysis-Induced Damage

Fibrosis is a general complication in many diseases. It is the main complication during peritoneal dialysis (PD) treatment, a therapy for renal failure disease. Local inflammation and mesothelial to mesenchymal transition (MMT) are well known key phenomena in peritoneal damage during PD. New data suggest that, in the peritoneal cavity, inflammatory changes may be regulated at least in part by a delicate balance between T helper 17 and regulatory T cells. This paper briefly reviews the implication of the Th17/Treg-axis in fibrotic diseases. Moreover, it compares current evidences described in PD animal experimental models, indicating a loss of Th17/Treg balance (Th17 predominance) leading to peritoneal damage during PD. In addition, considering the new clinical and animal experimental data, new therapeutic strategies to reduce the Th17 response and increase the regulatory T response are proposed. Thus, future goals should be to develop new clinical biomarkers to reverse this immune misbalance and reduce peritoneal fibrosis in PD.This work was supported in part by grants from Ministerio de Economia y competitividad SAF2010-21249 to Manuel López-Cabrera, Comunidad Autónoma de Madrid 2010-BMD2321 (FIBROTEAM) to Manuel Lopez Cabrera, and Fondo de Investigaciones Santitarias RETICS 06/0016 and PI 09/0064 to Rafael Selgas and FIS 12/01175 to Abelardo Aguilera Peralta. Georgios Liappas is fully supported from European Union, Seventh Framework Program “EuTRiPD,” under Grant Agreement PITN-GA-2011-287813. The authors would like to thank Juliette Siegfried and her team at ServingMed.com for editing the language of the paper.Peer Reviewe