Hepatic “Stem” Cells: Coming Full Circle

Teratani²,

et al. 2005

Hepatology

Hepatic differentiation at the molecular level is poorly understood, mainly because of the lack of a suitable model. Recently, using adherent monoculture conditions, we demonstrated the direct differentiation of hepatocytes from embryonic stem (ES) cells. In this study, we exploited the direct differentiation model to compare the gene expression profiles of ES cell-derived hepatocytes with adult mouse liver using DNA microarray technology. The results showed that the ES cell-derived hepatocyte gene expression pattern is very similar to adult mouse liver. Through further analysis of gene ontology categories for the 232 most radically altered genes, we found that the significant categories related to hepatic function. Furthermore, through the use of small interfering RNA technology in vitro, hepatocyte nuclear factor 3␤/FoxA2 was identified as having an essential role in hepatic differentiation. These results demonstrate that ES cell-derived hepatocytes recapitulate the gene expression profile of adult mouse liver to a significant degree and indicate that our direct induction system progresses via endoderm differentiation. In conclusion, our system closely mimics in vivo hepatic differentiation at the transcriptional level and could, therefore, be useful for studying the molecular basis of hepatocyte differentiation per se. At the molecular level, the induction of liver development and its progress is characterized by the expression of transcription factors, such as hepatocyte nuclear factors (HNFs), CCAAT/enhancer-binding proteins, and GATA-binding proteins. These so-called "liver-enriched" transcription factors show a specific expression pattern during organogenesis with a distinct narrow time interval of transcription initiation. 5,6 Recently, we established the direct differentiation of functional hepatocytes from an adherent monoculture condition of ES cells without forming embryoid bodies and clearly identified the growth factors that direct hepatic fate specification (the hepatic induction factor cocktail [HIFC] differentiation system) 7 based on the in vivo induction system. 8 These cells expressed several differentiation markers of mature hepatocytes and rescued experimental liver injury when they were transplanted into animals. Our next goal was to

Section: Discussionmentioning

confidence: 99%

Recapitulation ofin vivo gene expression during hepatic differentiation from murine embryonic stem cells

Teratani²,

et al. 2005

Hepatology

“…A more severe liver injury activates the endogenous stem cell population; these are often termed "oval" cells and are much smaller than mature hepatocytes (4). These oval cells display a distinct phenotype and have been shown to be a bipotential progenitor of two types of cells found in the liver, parenchymal hepatocytes and bile ductular epithelium (5,6). It appears that cells with regenerative potential constitute a small but significant population in both the adult and the developing liver (7), and further work is needed to render them more easily available.…”

mentioning

confidence: 99%

Side Population Cells Derived from Adult Human Liver Generate Hepatocyte-like Cells In Vitro

et al. 2005

We sought to determine whether hepatic side population (SP) cells derived from adult human liver possess the potential of a novel candidate hepatic stem cell. Human cadaveric donor liver was subjected to collagenase perfusion and hepatocytes were separated from nonparenchymal cells by differential centrifugation. SP cells were isolated from the nonparenchymal portion after Hoechst 33342 staining. Since CD45 is a panleukocyte antigen, CD45-negative SP cells were separated from the vast majority of CD45-positive SP cells (90%), and hepatic growth medium was used to culture both groups. Both CD45-negative and CD45-positive hepatic SP cells generated colonies in the hepatic growth medium in 2-3 weeks. The colonies yielded large cells morphologically consistent with human hepatocytes, demonstrating granule-rich cytoplasm, dense, often double nuclei, and intracellular lipofuscin pigment. The cultured cells from both sources were positive for markers of human hepatocytes: HepPar, cytokeratin 8 (CK8), and human albumin. Reverse transcriptasepolymerase chain reaction (RT-PCR) performed on both groups demonstrated positivity for additional liver markers including human albumin, CK18, α-1 anti-trypsin, and the human cytochrome P450 enzyme CYP2B6. Double immunostaining (CD45 and HepPar) and RT-PCR confirmed that the hepatocyte-like cells derived from the CD45-negative SP cells acquired HepPar positivity but had no detectable CD45 antigen expression. In contrast, the cultured cells derived from the CD45-positive SP cells also acquired HepPar positivity, but only a minimal fraction expressed the CD45 antigen. We conclude that hepatic SP cells derived from the nonparenchymal portion of human liver are a potential source of human hepatocytes irrespective of their CD45 status, and further animal studies will be required to assess their regenerative potential. Keywordshuman; side population; stem cells; hepatic; CD45 SP cells are identified by flow cytometry because of their unique ability to efflux Hoechst 33342 dye and have been shown in animal studies to be highly enriched stem cells (1,2). While the true adult liver stem cell has not been characterized, human hepatic side population (SP) cells might contain certain cells that might have hepatic progenitor-like properties. The liver in a normal healthy adult maintains a balance between cell gain and cell loss. It is composed mainly of two epithelial cell types, hepatocytes and bile ductular cells, both of which have high regenerative capacity. After hepatic injury, a regenerative process repairs the liver and brings it back to its original mass within 10 days (3). This restoration of mild to moderate cell loss and "wear and tear" renewal is largely achieved by hepatocyte self-replication. A more severe liver injury activates the endogenous stem cell population; these are often termed "oval" cells and are much smaller than mature hepatocytes (4). These oval cells display a distinct phenotype and have been shown to be a bipotential progenitor of two types of cells found ...

“…Similar to stem cells, progenitor cells retain the difsource of OCs (119,147), they have also been described as deriving from bone marrow (BM) (30,107). Other auferentiation potential and high proliferation capability, but they have lost the self-replication property.…”

Section: Introductionmentioning

confidence: 99%

Management of Liver Failure: From Transplantation to Cell-Based Therapy

et al. 2011

The severe shortage of deceased donor organs has driven a search for alternative methods of treating liver failure. In this context, cell-based regenerative medicine is emerging as a promising interdisciplinary field of tissue repair and restoration, able to contribute to improving health in a minimally invasive fashion. Several cell types have allowed long-term survival in experimental models of liver injury, but their therapeutic potential in humans should be regarded with deep caution, because few clinical trials are currently available and the number of patients enrolled so far is too small to assess benefits versus risks. This review summarizes the current literature on the physiological role of endogenous stem cells in liver regeneration and on the therapeutic benefits of exogenous stem cell administration with specific emphasis on the potential clinical uses of mesenchymal stem cells. Moreover, critical points that still need clarification, such as the exact identity of the stem-like cell population exerting the beneficial effects, as well as the limitations of stem cell-based therapies, are discussed.