title: Low-GDP peritoneal dialysis fluid ('balance') has less impact in vitro and ex vivo on epithelial-to-mesenchymal transition (EMT) of mesothelial cells than a standard fluid.
abstract: BACKGROUND
  Peritoneal membrane deterioration during peritoneal dialysis (PD) is associated with epithelial-to-mesenchymal transition (EMT) of mesothelial cells (MC), which is believed to be mainly due to glucose degradation products (GDPs) present in PD solutions. Here we investigate the impact of GDPs in PD solutions on the EMT of MC in vitro and ex vivo.
  
  
  METHODS
  For in vitro studies, omentum-derived MC were incubated with standard PD fluid or low-GDP solution diluted 1:1 with culture medium. For ex vivo studies, 33 patients, who were distributed at random to either the 'standard' or the 'low GDP' groups, were followed over 24 months. Effluents were collected every 6 months to determine EMT markers in effluent MC.
  
  
  RESULTS
  Exposure of MC to standard fluid in vitro resulted in morphological change into a non-epitheloid shape, down-regulation of E-cadherin, indicative of EMT, and in a strong induction of vascular endothelial growth factor (VEGF) expression. In contrast, in vitro exposure of MC to low-GDP solution did not lead to these phenotype changes. This could be confirmed ex vivo, as the prevalence of non-epitheloid phenotype of MC in the standard group was significantly higher with increasing PD duration and MC isolated from this group showed significantly higher levels of EMT-associated molecules including fibronectin, collagen I, VEGF, IL-8 and TGF-β levels when compared with the low-GDP group. Over time, the expression of E-cadherin also decreased in the standard but increased in the low-GDP group. In addition, the levels of EMT-associated molecules (fibronectin, VEGF and IL-8) increased in the standard but decreased in the low-GDP group. A similar trend was also observed for collagen I and for TGF-β (for the first year), but did not reach global statistical significance. Accordingly, effluent MC with non-epitheloid morphology showed significantly lower levels of E-cadherin and greater levels of fibronectin, collagen I, VEGF and IL 8 when compared with MC with epitheloid phenotype. The incidence of peritonitis did not significantly influence these results. Drop-out due to technique failure was less in the 'balance' group. The functional, renal and peritoneal evaluation of patients being treated with either standard or 'balance' fluid did not show any significant difference over time.
  
  
  CONCLUSIONS
  MC from PD effluent of patients treated with a PD fluid containing low GDP levels show fewer signs of EMT and the respective molecules than MC from patients treated with standard fluid, indicating a better preservation of the peritoneal membrane structure and a favourable outcome in patients using low-GDP fluid. It also confirms the hypothesis that the protection of EMT by GDP-reduced fluids is also present in vivo.
authors.affiliation: Unidad de Investigación and Servicio de Nefrología, Hospital Universitario La Paz, Madrid, Spain.
authors.forename: María Auxiliadora
authors.initials: MA
authors.lastname: Bajo
authors.forename: María Luisa
authors.initials: ML
authors.lastname: Pérez-Lozano
authors.forename: Patricia
authors.initials: P
authors.lastname: Albar-Vizcaino
authors.forename: Gloria
authors.initials: G
authors.lastname: del Peso
authors.forename: María-José
authors.initials: MJ
authors.lastname: Castro
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Gonzalez-Mateo
authors.forename: Antonio
authors.initials: A
authors.lastname: Fernández-Perpén
authors.forename: Abelardo
authors.initials: A
authors.lastname: Aguilera
authors.forename: Rafael
authors.initials: R
authors.lastname: Sánchez-Villanueva
authors.forename: J Antonio
authors.initials: JA
authors.lastname: Sánchez-Tomero
authors.forename: Manuel
authors.initials: M
authors.lastname: López-Cabrera
authors.forename: Mirjam E
authors.initials: ME
authors.lastname: Peter
authors.forename: Jutta
authors.initials: J
authors.lastname: Passlick-Deetjen
authors.forename: Rafael
authors.initials: R
authors.lastname: Selgas
mesh_terms: D015153:Blotting, Western; D015314:Dialysis Solutions / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D005260:Female; D005500:Follow-Up Studies; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D008297:Male; D008648:Mesoderm / Q000166:cytology* / Q000187:drug effects*; D008875:Middle Aged; D010530:Peritoneal Dialysis; D011379:Prognosis; D011446:Prospective Studies; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D015314:Dialysis Solutions; D012333:RNA, Messenger; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D005947:Glucose