Hepatocyte transplantation and drug-induced perturbations in liver cell compartments

Abstract

The potential for organ damage after using drugs or chemicals is a critical issue in medicine. To delineate mechanisms of drug-induced hepatic injury, we used transplanted cells as reporters in dipeptidyl peptidase IV-deficient mice. These mice were given phenytoin and rifampicin for 3 days, after which monocrotaline was given followed 1 day later by intrasplenic transplantation of healthy C57BL/6 mouse hepatocytes. We examined endothelial and hepatic damage by serologic or tissue studies and assessed changes in transplanted cell engraftment and liver repopulation by histochemical staining for dipeptidyl peptidase IV. Monocrotaline caused denudation of the hepatic sinusoidal endothelium and increased serum hyaluronic acid levels, along with superior transplanted cell engraftment. Together, phenytoin, rifampicin, and monocrotaline caused further endothelial damage, reflected by greater improvement in cell engraftment. Phenytoin, rifampicin, and monocrotaline produced injury in hepatocytes that was not apparent after conventional tissue studies. This led to transplanted cell proliferation and extensive liver repopulation over several weeks, which was more efficient in males compared with females, including greater induction by phenytoin and rifampicin of cytochrome P450 3A4 isoform that converts monocrotaline to toxic intermediates. Through this and other possible mechanisms, monocrotaline-induced injury in the endothelial compartment was retargeted to simultaneously involve hepatocytes over the long term. Moreover, after this hepatic injury, native liver cells were more susceptible to additional pro-oxidant injury through thyroid hormone, which accelerated the kinetics of liver repopulation. Conclusion: Transplanted reporter cells will be useful for obtaining insights into homeostatic mechanisms involving liver cell compartments, whereas targeted injury in hepatic endothelial and parenchymal cells with suitable drugs will also help advance liver cell therapy. ( T o obtain fresh paradigms in tissue homeostasis after exposure to drugs or chemicals, 1 we considered that reporter cells will help elucidate perturbations in the liver, because genetically marked reporter cells can be inserted into liver compartments, including the parenchyma or hepatic endothelium. 2-4 It was noteworthy that transplanted cells did not proliferate in the normal liver, where cell turnover is minimal, although, depending on the extent of injury in native cells, proliferation in healthy transplanted cells was activated. 5,6 In this way, transplanted cells could repopulate the liver, where in specific situations the kinetics of liver repopulation reflected loss of native hepatocytes. [7][8][9] In healthy animals, genotoxic manipulations were particularly effective in promoting such liver repopulation with healthy cells. However, further insights are necessary to obtain pharmacologic approaches for repopulating the liver, particularly for clinical applications.To develop cell compartment-specific hepatic perturbations, we used monocrotaline (...

Perturbations in Ataxia Telangiectasia Mutant Signaling Pathways After Drug-Induced Acute Liver Failure and Their Reversal During Rescue of Animals by Cell Therapy

“…injections (in normal saline) of Rif (75 mg/kg) and Phen (30 mg/kg), followed on day 4 by MCT (100 -150 mg/kg), as previously described. 6 …”

“…6,8 Cell viability was tested by trypan blue dye exclusion and was 80% or greater. For cell transplantation studies, NOD/SCID mice treated with Rif-Phen-MCT were given 5 ϫ 10 6 to 50 ϫ 10 6 cells i.p., along with 1-ml microcarriers (Cytodex 3; Amersham Biosciences Corp, Piscataway, NJ) in a total volume of 1.2 to1.5 ml.…”

“…Bacterial ␤-galactosidase (LacZ), glycogen, and glucose-6-phosphatase were stained histochemically, as previously described. 6,18 Immunostainings were for p21 …”

“…6 However, when we sought to reproduce this Rif-Phen-MCT-induced liver injury in mice with severe combined immune deficiency (SCID) mutation in the protein kinase, DNA-activated, catalytic polypeptide (Prkdc scid /J), we instead observed ALF, with mortality over several days. Characterization of the nature of this liver injury and analysis of underlying molecular mechanisms demonstrated that strain-specific regulation of gene expression accounted for differences in outcomes of Rif-Phen-MCT-induced hepatotoxicity in C57BL/6 mice versus these NOD/SCID (C3H/He) mice.…”

“…Cell transplantation in liver sinusoids may even be undesirable in ALF because occlusion of blood flow by transplanted cells might worsen hepatic injury. [11][12][13][14] Moreover, transplanted hepatocytes integrate in liver parenchyma over several days and take far longer to proliferate, 6,8 casting doubt on the importance of reseeding of the liver in ALF. By contrast, spacious extrahepatic sites (eg, the peritoneal cavity) may accommodate many transplanted cells.…”