Biocompatibility of a Bicarbonate/Lactate-Buffered PD Fluid Tested with a Double-Chamber Cell Culture System

Abstract

Objective In peritoneal dialysis (PD), neutrally buffered PD fluids with lower concentrations of glucose degradation products (GDP) have tested superior to conventional fluids in terms of biocompatibility. However, conventional in vitro studies provoke debate because, due to the lack of subsequent equilibration with the blood, they do not resemble the true intraperitoneal situation of PD. Methods We established a double-chamber cell culture system with peritoneal mesothelial cells seeded on top of a permeable membrane, with a physiological buffer below. Thus adequately reflecting the in vivo equilibration pattern, we compared a conventional fluid with a neutral bicarbonate/lactate-buffered PD solution. Using an exchange pattern adapted from an 8-hour continuous ambulatory PD regimen, cell viability was assessed with an MTT assay, and cell function via constitutive and stimulated interleukin (IL)-6 release. As an indicator of potential induction of fibrosis and as a parameter of mesothelial cell integrity, respectively, transforming growth factor-beta 1 (TGF-β1) generation and cancer antigen 125 (CA125) release were measured. Results The conventional solution significantly compromised mesothelial cell viability and function in terms of mitochondrial activity ( p < 0.05) and stimulated IL-6 release ( p < 0.05). The bicarbonate/lactate fluid had no effect on cell viability or IL-6 release and turned out to be equivalent to the properties of the growth medium. Whereas lactate-incubated cells did not respond to IL-1β stimulation, bicarbonate/lactate-treated cells adequately increased IL-6 release after stimulation ( p < 0.0005). Release of TGF-β1 and CA125 did not differ between the different fluids and the control. Conclusions Due to the sustained equilibration process, the double-chamber cell culture model allows a more realistic insight into mesothelial cell viability and function in terms of PD. As in classic in vitro studies, an adverse effect of conventional PD solutions on mesothelial cells was overt in the present cell culture system. The neutral bicarbonate/lactate-buffered fluid with low GDP content, however, did not interfere with mesothelial cell vitality or function, indicating superior biocompatibility.