Liver repopulation with bone marrow derived cells improves the metabolic disorder in the Gunn rat.

BACKGROUND: Reversible ischaemia/reperfusion (I/R) liver injury has been used to induce engraftment and hepatic parenchymal differentiation of exogenous beta2-microglubulin(-)/Thy1(+) bone marrow derived cells. AIM: To test the ability of this method of hepatic parenchymal repopulation, theoretically applicable to clinical practice, to correct the metabolic disorder in a rat model of congenital hyperbilirubinaemia. METHODS AND RESULTS: Analysis by confocal laser microscopy of fluorescence labelled cells and by immunohistochemistry for beta2-microglubulin, 72 hours after intraportal delivery, showed engraftment of infused cells in liver parenchyma of rats with I/R, but not in control animals with non-injured liver. Transplantation of bone marrow derived cells obtained from GFP-transgenic rats into Lewis rats resulted in the presence of up to 20% of GFP positive hepatocytes in I/R liver lobes after one month. The repopulation rate was proportional to the number of transplanted cells. Infusion of GFP negative bone marrow derived cells into GFP positive transgenic rats resulted in the appearance of GFP negative hepatocytes, suggesting that the main mechanism underlying parenchymal repopulation was differentiation rather than cell fusion. Transplantation of wild type bone marrow derived cells into hyperbilirubinaemic Gunn rats with deficient bilirubin conjugation after I/R damage resulted in 30% decrease in serum bilirubin, the appearance of bilirubin conjugates in bile, and the expression of normal UDP-glucuronyltransferase enzyme evaluated by polymerase chain reaction. CONCLUSIONS: I/R injury induced hepatic parenchymal engraftment and differentiation into hepatocyte-like cells of bone marrow derived cells. Transplantation of bone marrow derived cells from non-affected animals resulted in the partial correction of hyperbilirubinaemia in the Gunn rat.

Bilirubin inhibits bile acid induced apoptosis in rat hepatocytes.

BACKGROUND AND AIMS: Hydrophobic bile acids contribute to hepatocellular injury in cholestasis and rapidly induce apoptosis in vitro; however, unlike Fas agonists, cholestasis does not cause extensive hepatocyte apoptosis. As antioxidants provide protection against bile acid induced liver injury, our premise was that bilirubin, a free radical scavenger with increased plasma levels in the presence of liver disease, could protect hepatocytes against bile acid induced apoptosis. METHODS: Freshly isolated rat hepatocytes were incubated for four hours with 100 micromol/l glycochenodeoxycholate (GCDC) alone or with increasing concentrations of unconjugated (UCB) or conjugated (CB) bilirubin. RESULTS: Both UCB and CB inhibited GCDC induced apoptosis in a dose dependent fashion and suppressed the generation of reactive oxygen species by hepatocytes. CONCLUSIONS: The antiapoptotic effect of bilirubin associated with its antioxidant properties indicates that hyperbilirubinaemia may have a protective role in liver disease.

Isolation, characterization, and transplantation of bone marrow-derived hepatocyte stem cells.

Recently it was shown that a population of cells in the bone marrow-expressing hematopoietic stem cell antigens could differentiate into hepatocytes. However, explicitly committed hepatocyte progenitors, which exhibit highly differentiated liver functions, immediately upon isolation, have not yet been isolated from bone marrow. After studying common antigens on blast-like cells in fetal and adult regenerating cholestatic rat livers and human regenerating and malignant livers, we hypothesized that beta-2-microglobulin-negative (beta(2)m(-)) cells might represent dedifferentiated hepatocytes and/or their progenitors. Utilizing a two-step magnetic bead cell-sorting procedure, we show that in bone marrow from rat and human, beta(2)m(-)/Thy-1(+) cells consistently express liver-specific genes and functions. After intraportal infusion into rat livers, bone marrow-derived hepatocyte stem cells (BDHSC) integrated with hepatic cell plates and differentiated into mature hepatocytes. In a culture system simulating liver regeneration and containing cholestatic serum, these cells differentiated into mature hepatocytes and metabolized ammonia into urea. This differentiation was dependent on a yet nondescript humoral signal existing in the cholestatic serum. Transmission electron microscopy and three-dimensional digital reconstruction confirmed hepatocyte ultrastructure of cultured BDHSC.

Comparison of pig, human and rat hepatocytes as a source of liver specific metabolic functions in culture systems--implications for use in bioartificial liver devices.

The limited availability of human hepatocytes results in the use of animal cells in most bioartificial liver support devices. In the present work, clinically relevant liver specific metabolic activities were compared in rat, pig and human hepatocytes cultured on liver-derived biomatrix to optimize the expression of differentiated functions. Pig hepatocytes showed higher rates of diazepam metabolism (2.549+/-0.821 microg/h/million cells vs. 0.474+/-0.079 microg/h/million cells rats, p<0.005, and vs. 0.704+/-0.171 microg/h/million cells in man, p<0.005) and of bilirubin conjugation (21.60116+/-8.433237 micromoles/l/24 h vs. 6.786809+/-2.983758 in man, p<0.001 and vs. 9.956538+/-1.781016 micromoles/l/24 h in rats, p<0.005). Urea synthesis was similar in pig and in human hepatocytes (150+/-46.3 vs. 144.8+/-21.46 nmoles/h/million cells) and it was lower in rats (84.38+/-35.2; p<0.001 vs. man, p<0.02 vs. pig). High liver specific metabolic activities in cultured pig hepatocytes further support their use as a substitue for human cells in bioartificial liver devices.