Faculty Bibliography

AIMS: Combined hepatocellular/cholangiocarcinomas have been explained by some investigators as bidirectional differentiation of neoplastic progenitor cell populations. The presence of hepatic progenitor cells has now been confirmed in humans, though whether they can give rise to malignant tumours has not been confirmed. We report four cases of small tumours identified in livers with features of chronic hepatitis which may suggest a role for malignant transformation of hepatic stem cells in hepatic malignancies. METHODS: Tumour samples were studied from four patients by histochemistry and immunohistochemistry. RESULTS: Two patients had chronic hepatitis B, one had chronic hepatitis C and chronic alcoholic liver injury, and one had non-B non-C chronic hepatitis. Stages of disease ranged from portal fibrosis to cirrhosis. All tumours contained undifferentiated cells with morphological and immunohistochemical features that would be expected of hepatic progenitor cells. These cells merged with both hepatocellular carcinoma and cholangiocarcinoma components as well as with mature appearing hepatocytes within the tumours. CONCLUSION: We suggest that these tumours are of hepatic progenitor cell origin, supporting the concepts that human hepatocarcinogenesis can be based on transformation of progenitor cells and that such a process may underlie development of some mixed hepatocellular/cholangiocarcinomas and dysplastic nodules

BACKGROUND/AIMS: In massive hepatic necrosis, hepatic stem cells constitute a canal of Hering derived, cytokeratin 19 (CK19) positive 'ductular reaction' (DR). Whether DRs in cirrhosis are activated stem cells (so called 'buds') or biliary metaplasia of cholestatic, injured hepatocytes is still debated. We investigate derivation of intraseptal hepatocytes (ISHs) from DRs and from the biliary tree in cirrhosis. METHODS: Explants of hepatitis B and C, alcohol, primary biliary cirrhosis and primary sclerosing cholangitis-related cirrhosis were examined. ISHs were quantified and their associations with DRs and cholestasis recorded. 3D-reconstruction of ISHs and nearby bile ducts was performed in blocks from hepatitis C and primary sclerosing cholangitis cirrhosis. RESULTS: Seven hundred seventy five/830 (94%) ISHs were associated with CK19 positive DRs. ISHs without ductular reactions were more likely to show cholestatic features (P<0.0001). In 3D, ISHs were seen to bud directly from the biliary tree. In summary: ISHs: (1) are usually associated with stem cell-like DRs; (2) are rarely cholestatic, leaving the associated DRs unexplained; and (3) are linked to the biliary tree in 3D. Dynamic proliferation rates in hepatitis C over time suggest that hepatocyte replication diminishes in late stages, with an associated activation of the biliary stem cell compartment. CONCLUSIONS: We therefore suggest that the biliary tree, from at least its smaller branches up to the canals of Hering, are composed of or at least harbor facultative hepatic stem cells, and that ISH largely represent 'buds' of newly formed hepatocytes

The degree to which these elephants are disruptive to the steady advancement of the adult stem cell field will become clear with time. In some ways they enliven the discourse, but in many ways they interfere with efficient progress. Naming these elephants is a first step toward dealing with them. If we remain aware of these issues when evaluating new research, we are less likely to make careless mistakes, and we are more likely to be able to hold scientists, politicians, journalists, and entrepreneurs accountable for their practices. Although all adult stem cell researchers will spend time profitably riding some of these elephants, we will all inevitably spend more time cleaning up after them. Perhaps open, careful, and unbiased discussions of these elephants will help the cleanup work be less odious and completed sooner, rather than later

BACKGROUND AND AIMS: Dysplastic nodules (DN) may be divided into high-grade and low-grade, and the former has been known as a precancerous or borderline lesion. Recently many morphological characteristics concerning these types of DN have been reported. In the present study we attempted to evaluate the scirrhous change in DN as an indicative feature of high-grade DN, based on the morphological and cell-kinetic analyses using immunohistochemical stains for Ki-67. METHODS: We reviewed 35 livers with DN and selected 15 DN with scirrhous change. We stained DN-bearing sections of each case with hematoxylin and eosin, trichrome, reticulin and Perls' stain. We tried to subclassify and characterize the scirrhous change according to the fibrosis pattern. We also stained with Ki-67 immunohistochemically to assess the proliferative activity of DN with scirrhous change. RESULTS: We found two types of scirrhous change, that is, pericellular and stellate. The pericellular type was related to the Mallory body-forming cholestatic degeneration, whereas the stellate type was associated with extensive portal fibrosis probably induced by ischemic damage. Among DN with scirrhous change, high-grade DN comprised five nodules (33%) and there were 10 (67%) low-grade nodules. There was no significant relationship between the presence or the types of scirrhous change and the grade of DN. The significant differences of Ki-67 labeling indices between types of scirrhous change were not shown in this study. We also could not find the differences between Ki-67 labeling indices of scirrhous DN (high and low grades) and those of surrounding regenerative nodules. CONCLUSIONS: This evidence indicated that the scirrhous change in DN was not a specific feature of high-grade DN. We also found that scirrhous DN have two morphological varieties that may represent biologically different processes, that is, pericellular scirrhous type and stellate scirrhous type

It is now understood that there are three cell compartments which physiologically contribute to vertebrate liver parenchymal maintenance and regeneration after injury: mature liver cells (hepatocytes, cholangiocytes), intraorgan stem/progenitor cells (cells of the proximal biliary tree, periductal cells) and extraorgan stem cells (from the circulation and the bone marrow). All of these cell populations, as well as other, non-physiologic stem cells (e.g., mesenchymal stromal cells from the bone marrow, fetal hepatoblasts, embryonic stem [ES] cells), may be used therapeutically for treatment of inherited and acquired liver diseases. This article will summarise our current understanding of these various cell populations, and review possible approaches to their therapeutic use, including cell transplantation, bioartificial liver devices (BLDs), gene therapy and administration of exogenous factors to stimulate normal physiological responses to repair

Bone marrow harbors cells that have the capacity to differentiate into cells of nonhematopoietic tissues of neuronal, endothelial, epithelial, and muscular phenotype. Here we demonstrate that bone marrow-derived cells populate pancreatic islets of Langerhans. Bone marrow cells from male mice that express, using a CRE-LoxP system, an enhanced green fluorescent protein (EGFP) if the insulin gene is actively transcribed were transplanted into lethally irradiated recipient female mice. Four to six weeks after transplantation, recipient mice revealed Y chromosome and EGFP double-positive cells in their pancreatic islets. Neither bone marrow cells nor circulating peripheral blood nucleated cells of donor or recipient mice had any detectable EGFP. EGFP-positive cells purified from islets express insulin, glucose transporter 2 (GLUT2), and transcription factors typically found in pancreatic beta cells. Furthermore, in vitro these bone marrow-derived cells exhibit - as do pancreatic beta cells - glucose-dependent and incretin-enhanced insulin secretion. These results indicate that bone marrow harbors cells that have the capacity to differentiate into functionally competent pancreatic endocrine beta cells and that represent a source for cell-based treatment of diabetes mellitus. The results generated with the CRE-LoxP system also suggest that in vivo cell fusion is an unlikely explanation for the 'transdifferentiation' of bone marrow-derived cells into differentiated cell phenotypes

The capacity of hepatocytes and cholangiocytes to contribute to their own maintenance has long been recognized. More recently, studies have indicated the presence of both intra-hepatic and extra-hepatic stem/progenitor cell populations. The intraorgan compartment probably derives primarily from the biliary tree, most particularly the most proximal branches, i.e. the canals of Hering and smallest ductules. The extra-organ compartment is at least in part derived from diverse populations of cells from the bone marrow. These three tiers of liver cell regeneration serve to maintain the normal organ and to regenerate damaged parenchyma in response to a variety of insults. The nature and extent of the insult determines the balance between these stem/progenitor compartments