Exogenous thyroid hormone induces liver enlargement, whilst maintaining regenerative potential--a study relevant to donor preconditioning.

We have investigated thyroid hormone- (T3) induced liver cell hyperplasia in rats to explore the potential utility of primary mitogens within the clinical context of donor conditioning prior to living-related transplantation. A single injection of T3 induced a semi-synchronized proliferative response in hepatocytes, resulting at 10 days in a peak increase in liver mass, liver/body mass ratio, total DNA and total protein. Importantly, the hyperplastic liver induced by T3 exhibits a commensurate increase in metabolic capacity, as assessed by enhanced galactose elimination capacity. Furthermore, when the liver mass had been increased by an injection of T3 given 10 days previously and 70% partial hepatectomy performed, there was a larger remnant liver mass, liver/body mass ratio, total DNA and total protein content 24 h after surgery, compared with animals given a control injection. Interestingly, the regenerative response to surgery was the same in both groups, indicating that prior T3 conditioning did not impair the regenerative response of the liver. Using more stringent conditions to test hepatic functional reserve, following 90% hepatectomy, there was a greater (57%) survival in animals pre-treated with T3 compared to 14% in controls.

Altered mitochondrial function and cholesterol synthesis influences protein synthesis in extended HepG2 spheroid cultures.

Cultures of hepatocytes and HepG2 cells provide useful in vitro models of liver specific function. In this study, we investigated metabolic and biosynthetic function in 3-D HepG2 spheroid cultures, in particular to characterise changes on prolonged culture. We show that HepG2 cells cultured in spheroids demonstrate a reduction in mitochondrial membrane potential and respiration following 10 days of culture. This coincides with a modest reduction in glycolysis but an increase in glucose uptake where increased glycogen synthesis occurs at the expense of the intracellular ATP pool. Lowered biosynthesis coincides with and is linked to mitochondrial functional decline since low glucose-adapted spheroids, which exhibit extended mitochondrial function, have stable biosynthetic activity during extended culture although biosynthetic function is lower. This indicates that glucose is required for biosynthetic output but sustained mitochondrial function is required for the maintenance of biosynthetic function. Furthermore, we show that cholesterol synthesis is markedly increased in spheroids cf. monolayer culture and that inhibition of cholesterol synthesis by lovastatin extends mitochondrial and biosynthetic function. Therefore, increased cholesterol synthesis and/or its derivatives contributes to mitochondrial functional decline in extended HepG2 spheroid cultures.

Modulation of hepatocyte function in an immortalized human hepatocyte cell line following exposure to liver-failure plasma.

For hepatocytes to function effectively in a bioartificial liver device, maintained function in the milieu of plasma from patients with liver failure will be required. We have investigated the effect of plasma obtained at plasmapheresis from patients with acute liver failure on the performance of the human hepatocyte cell line HHY41 in liver-failure plasma, normal plasma, and culture medium. Cytotoxicity of plasma, DNA synthesis by thymidine incorporation, oxidative status, and cytochrome P450 functions were assayed after a 16 h culture with normal plasma, liver-failure plasma, or culture medium. Some, but not all, samples of liver-failure plasma were deleterious to the performance of the cell line, inducing cytotoxicity and oxidative stress, with diminished DNA synthesis, protein synthesis, and cytochrome P4501A activity. Strategies to minimize the toxic effects of liver-failure plasma may improve the performance of liver cells in extracorporeal liver-support devices.