Genetically marked hepatocytes from dipeptidyl peptidase (DPP) IV؉ Fischer 344 rats were transplanted into the liver of DPPIV ؊ mutant Fischer 344 rats after a combined treatment with retrorsine , a pyrrolizidine alkaloid that blocks the hepatocyte cell cycle, and two-thirds partial hepatectomy. In female rats , clusters of proliferated DPPIV ؉ hepatocytes containing 20 to 50 cells/cluster , mostly derived from single transplanted cells , were evident at 2 weeks , increasing in size to hundreds of cells per cluster at 1 month and 1000 to several thousand cells per cluster at 2 months, representing 40 to 60% of total hepatocyte mass. This level of hepatocyte replacement remained constant for up to 1 year , the duration of experiments conducted. In male rats , liver replacement occurred more rapidly and was more extensive , with transplanted hepatocytes representing 10 to 15% of hepatocyte mass at 2 weeks , 40 to 50% at 1 month , 90 to 95% at 2 months , 98% at 4 months , and 99% at 9 months.

When differentiated in the presence of activin A in serum-free conditions, mouse embryonic stem cells efficiently generate an endoderm progenitor population defined by the coexpression of either Brachyury, Foxa2 and c-Kit, or c-Kit and Cxcr4. Specification of these progenitors with bone morphogenetic protein-4 in combination with basic fibroblast growth factor and activin A results in the development of hepatic populations highly enriched (45-70%) for cells that express the alpha-fetoprotein and albumin proteins. These cells also express transcripts of Afp, Alb1, Tat, Cps1, Cyp7a1 and Cyp3a11; they secrete albumin, store glycogen, show ultrastructural characteristics of mature hepatocytes, and are able to integrate into and proliferate in injured livers in vivo and mature into hepatocytes expressing dipeptidyl peptidase IV or fumarylacetoacetate hydrolase. Together, these findings establish a developmental pathway in embryonic stem cell differentiation cultures that leads to efficient generation of cells with an immature hepatocytic phenotype.

Hematopoietic stem cells rarely contribute to hepatic regeneration, however, the mechanisms governing their homing to the liver, which is a crucial first step, are poorly understood. The chemokine stromal cell-derived factor-1 (SDF-1), which attracts human and murine progenitors, is expressed by liver bile duct epithelium. Neutralization of the SDF-1 receptor CXCR4 abolished homing and engraftment of the murine liver by human CD34 + hematopoietic progenitors, while local injection of human SDF-1 increased their homing. Engrafted human cells were localized in clusters surrounding the bile ducts, in close proximity to SDF-1-expressing epithelial cells, and differentiated into albumin-producing cells. Irradiation or inflammation increased SDF-1 levels and hepatic injury induced MMP-9 activity, leading to both increased CXCR4 expression and SDF-1-mediated recruitment of hematopoietic progenitors to the liver. Unexpectedly, HGF, which is increased following liver injury, promoted protrusion formation, CXCR4 upregulation, and SDF-1-mediated directional migration by human CD34 + progenitors, and synergized with stem cell factor. Thus, stress-induced signals, such as increased expression of SDF-1, MMP-9, and HGF, recruit human CD34 + progenitors with hematopoietic and/or hepatic-like potential to the liver of NOD/SCID mice. Our results suggest the potential of hematopoietic CD34 + /CXCR4 + cells to respond to stress signals from nonhematopoietic injured organs as an important mechanism for tissue targeting and repair.

We used recombinant-DNA technology and gel electrophoresis to find hepatitis B virus DNA (HBV-DNA) in liver and tumor tissue from patients with hepatocellular carcinoma and chronic liver disease, and to study the integration of HBV-DNA into the genome of these tissues' cells. In 12 patients with hepatocellular carcinoma who had hepatitis B surface antigen (HBsAg) in their serum, integrated HBV-DNA was identified in the tumors; it was also found in tumors from three of eight patients who were seronegative for HBsAg but positive for antibody to HBsAg. In some cases, integrated HBV-DNA was also present in nontumorous liver tissue that had the same hybridization pattern or one different from that of the tumor. In five carriers of HBsAg who had evidence of the carrier state and chronic liver disease for less than two years, HBV-DNA was present but not integrated in liver tissue. In the two patients who had carried HBsAg for more than eight years, HBV-DNA was integrated into the host genome. These data suggest that integration of HBV-DNA into hepatocytes occurs during the course of persistent HBV infection and precedes development of gross neoplasm.

It has recently been shown that hepatitis B virus (HBV) contains a transcriptional enhancer element. In order to determine whether this enhancer responds to

Hematopoietic stem cells rarely contribute to hepatic regeneration, however, the mechanisms governing their homing to the liver, which is a crucial first step, are poorly understood. The chemokine stromal cell–derived factor-1 (SDF-1), which attracts human and murine progenitors, is expressed by liver bile duct epithelium. Neutralization of the SDF-1 receptor CXCR4 abolished homing and engraftment of the murine liver by human CD34+ hematopoietic progenitors, while local injection of human SDF-1 increased their homing. Engrafted human cells were localized in clusters surrounding the bile ducts, in close proximity to SDF-1–expressing epithelial cells, and differentiated into albumin-producing cells. Irradiation or inflammation increased SDF-1 levels and hepatic injury induced MMP-9 activity, leading to both increased CXCR4 expression and SDF-1–mediated recruitment of hematopoietic progenitors to the liver. Unexpectedly, HGF, which is increased following liver injury, promoted protrusion formation, CXCR4 upregulation, and SDF-1–mediated directional migration by human CD34+ progenitors, and synergized with stem cell factor. Thus, stress-induced signals, such as increased expression of SDF-1, MMP-9, and HGF, recruit human CD34+ progenitors with hematopoietic and/or hepatic-like potential to the liver of NOD/SCID mice. Our results suggest the potential of hematopoietic CD34+/CXCR4+cells to respond to stress signals from nonhematopoietic injured organs as an important mechanism for tissue targeting and repair

No abstract

To evaluate the role of maternal hepatitis B virus (HBV) DNA levels in perinatal infection, two nested case-control studies were done within a cohort of 773 hepatitis B surface antigen (HBsAg)-positive Taiwanese women and their infants. As serum HBV DNA levels increased from < 0.005 to > or = 1.4 ng/mL among the hepatitis B e antigen (HBeAg)-positive mothers, the odds ratio (OR) for having a persistently infected infant increased from 1.0 to 147.0 (P for trend < .001). Among HBeAg-negative mothers, the OR for having a persistently infected infant was 19.2 (95% confidence interval, 2.3-176.6) in mothers with high versus low levels of serum HBV DNA. A logistic regression analysis identified maternal HBV DNA to be a stronger independent predictor of persistent infection than HBeAg status. Thus, perinatal exposure to high levels of maternal HBV DNA is the most important determinant of infection outcome in the infant.