Development of bioartificial liver: bilirubin conjugation in Gunn rats

We developed a novel bioartificial liver using microcarrier-attached hepatocytes and a bioreactor. The bioreactor consists of an intracapillary chamber made up of porous (0.2 micron) cellulose acetate hollow fibers enclosed in a polycarbonate module forming an extracapillary chamber. Cryopreserved (-80 degrees C, 3 weeks) microcarrier-attached hepatocytes (3-4 X 10(7] were inoculated into the extracapillary chamber. The bioartificial liver, containing either microcarrier hepatocytes (n = 6) or microcarriers alone (n = 5); was attached to adult Gunn rats via cannulas in the aorta and inferior vena cava. Bile samples were collected before and at hourly intervals after attachment to the bioartificial liver. The same animal model was used to demonstrate de novo conjugation of free bilirubin by the bioartificial liver (n = 3) following systemic administration of unconjugated [3H]bilirubin. Bile was analyzed for bilirubin mono- and diglucuronides by high-performance liquid chromatography and confirmed by digestion with beta-glucuronidase and cochromatography with normal rat bile. A progressive increase in the concentration of bilirubin monoglucuronide and bilirubin diglucuronide in bile was seen as early as 30 min and lasted up to 4 hr following attachment to a bioartificial liver containing microcarrier hepatocytes (3.53 +/- 0.68 to 8.07 +/- 0.85 microM; P less than 0.01). Approximately 22% of the radiolabeled bilirubin excreted in bile was seen in the form of bilirubin conjugates, no radioactivity was seen in the free bilirubin fraction. In conclusion, we developed a bioartificial liver using microcarrier hepatocytes which carry out an important differentiated liver function which results in partial correction of a specific metabolic liver defect, i.e., conjugation of bilirubin.