Effects of Osmolality and Osmotic Agents on Viability and Proliferation of Human Peritoneal Mesothelial Cells

Cha, Mi Kyung; Ha, Hunjoo; Yu, Mi Ra; Choi, Hoo Nam; Lee, Hi Bahl

Abstract

High glucose activates protein kinase C, induces reactive oxygen species generation, and upregulates expression of transforming growth factor-beta1(TGF-beta1) and fibronectin by human peritoneal mesothelial cells(HPMC). High glucose also induces premature senescence in mesothelial cells. Mesothelial cells shrink after exposure to hypertonic medium and intracellular uptake of amino acids increase to ensure subsequent volume increase. Based on these observations, new and more biocompatible peritoneal dialysis solutions that are glucose free and/or iso-osmolar have been developed. We investigated the effects of different osmolality and different osmotic agents including glucose, mannitol, and icodextrin on viability and proliferation of HPMC. HPMC were obtained from the omental tissues of consenting patients undergoing Cesarean section or elective abdominal surgery. All experiments were performed using cells in the 2nd or 3rd passage. Near-confluent HPMC grown in culture dishes were incubated with serum-free medium for 48 hours to arrest and synchronize cell growth. Lactate dehydrogenase(LDH) release was measured for cell viability and [3H]-thymidine incorporation for proliferation of cultured HPMC, after exposing HPMC to different concentrations of glucose, mannitol, and icodextrin for up to 96 hours. High glucose and mannitol at concentrations up to 100 mM(375 mOsm) did not increase LDH release up to 96 hours compared to control M199. When HPMC were exposed to 2, 4, 7.5, and 9% of icodextrin for 24-96 hours, LDH release did not increase. Glucose at 30, 50, and 100 mM significantly inhibited [3H]-thymidine incorporation by HPMC at 24 and 48 hours. Mannitol at 30, 50, and 100 mM for 24 hours and at only 100 mM for 48 hours also significantly inhibited cell proliferation. Icodextrin 9% (305 mOsm) inhibited cell proliferation compared with control M-199 at 24 hours. In conclusion, high osmolality per se dose not appear to increase HPMC death. However, high osmolality appears to inhibit HPMC proliferation at early stage. In addition, high glucose appears to inhibit HPMC proliferation independent of osmolality since high glucose continues to inhibit cell proliferation at 48 and 72 hours when mannitol at the same concentration did not. Icodextrin 9% of which osmolality is 305 mOsm inhibits HPMC proliferation at early stage but does not appear to increase HPMC death.