Urea-cycle enzymes are expressed in two human hepatocyte cell lines when grown three-dimensionally, but not as monolayers

Abstract

UREA-CYCLE ENZYMES ARE EXPRESSED IN TWO HUMAN HEPATOCYTE CELL LINES WHEN GROWN THREE-DIMENSIONALLY, BUT NOT AS MONOLAYERS M. Khalil, H.J.E Hodgson, C. Selden Liver Group, ICSM, Hammersmith Hosp., Du Cane Road, London, WI2 ONN, UK. A cell source for use in a bioartificial liver is still under scrutiny. Human hepatocyte cell lines remain as potential candidates. However, an ability of cell lines to perform liverspecific functions is required. Urea-cycle enzyme specific activities were measured in two human hepatocyte cell lines, as one indication of the detoxification capacity of these cell lines. Monolayer and 3D encapsulated HepG2 and HHY41 cells were assessed for Carbamyl phosphate synthetase (CPS), omithine transcarbamylase (OTC), argininosuceinate synthetase (ASS), argininosuccinase (AS) and arginase. Monolayer cells did not express any of the enzymes. The 3D I-IHY41 cells demonstrated all 5 enzymes (see table) at levels comparable with rat liver in vivo. The 3D HepG2 cells showed similar activities, except for OTC, which was andetectable. Etmyme Activity (units /mg protein / h) CPS OTC ASS AS Arginase Rat Liver 1.0 ± .06 17.4 + 1.3 .2 + .01 1.8 + .10 207:t: 8.3 3D HepG2 0.5 5:.06 u.d. .2 + .01 1.4 5:.03 695:14.2 3DLG6 0.65:.01 5.8:1:0.6 .1 :L.02 1.3_+.04 525:7.7 Growing human hepatocyte cell lines as spheroids improves the function of these cells to levels approaching that in vivo, an important aspect for development of a bioartificial liver. I P/C03/23 I