Faculty Bibliography

Toll-like receptors (TLRs) may play a role in the inflammatory patterns observed in primary biliary cirrhosis (PBC) and chronic hepatitis C (CHC). We investigated TLR 3, 4 and 9 expression in PBC and CHC using immunohistochemical staining. METHODS: Patient biopsies of PBC (N=11) and CHC (N=15) were compared to disease free livers (n=7). The extent of TLR staining was assessed separately according to a semi-quantitative scale for hepatocytes, cholangiocytes and portal mononuclear cells (PMC). RESULTS: In hepatocytes, TLR4 expression was increased (PBC; P=0.019), as was TLR9 (PBC; P=0.006, CHC; P=0.001). Cholangiocyte expression of TLRs 4 and 3 was reduced in both PBC (TLR4; P<0.0001, TLR3; P=0.006) and CHC (TLR4; P<0.0001, TLR3; P=0.014). Cholangiocyte expression of TLR9 was elevated for both groups and was significant in CHC (P=0.0115). PMCs showed up-regulation of TLR9 in PBC (P=0.022) and CHC (P=0.0001), with almost no expression of TLR 3 or 4. CONCLUSIONS: In PBC and CHC, hepatocytes showed increased TLR 4 and 9 expression without change in TLR3. Cholangiocytes showed increased TLR9 expression as opposed to down-regulation of TLRs 3 and 4. PMCs in both diseases had significantly increased TLR 9 expression perhaps implicating TLR9 expression in chronic liver inflammation.

Russell bodies are pink eosinophilic accumulations within plasma cells. To date, two hypotheses have attempted to elucidate the biological events behind the formation of these bodies. One theory sustains that such bodies constitute cytoplasmic accumulation of immunoglobulin derivatives contained in the perinuclear cistern of the smooth endoplasmic reticulum because of an increased synthesis or altered secretion. On the other hand, since its initial description in the medical literature, several authors have attributed the formation of such bodies to the presence of microorganisms such as in the case of Russell body gastritis and its association to Helicobacter pylori infection. In an attempt to possibly characterize the presence of an infectious organism, we performed a thorough biomolecular analysis on a case of a 69-year-old female presenting with Russell body duodenitis which, to the best of our knowledge, constitutes the second report of this clinical entity in the English literature. In light that the events behind formation of such bodies in H. pylori-negative individuals remain unclear, we hypothesize on the possible pathways that could have led to their reactive mechanical and immune derivation.

The role of progenitor cells in liver repair and fibrosis has been extensively described, but their purification remains a challenge, hampering their characterization and use in regenerative medicine. To address this issue, we developed an easy and reproducible liver progenitor cell (LPC) isolation strategy based on aldehyde dehydrogenase (ALDH) activity, a common feature shared by many progenitor cells. We demonstrate that a subset of nonparenchymal mouse liver cells displays high levels of ALDH activity, allowing the isolation of these cells by fluorescence-activated cell sorting. Immunocytochemistry and qPCR analyses on freshly isolated ALDH(+) cells reveal an enrichment in cells expressing liver stem cell markers such as EpCAM, CK19, CD133, and Sox9. In culture, the ALDH(+) population can give rise to functional hepatocyte-like cells as illustrated by albumin and urea secretion and cytochrome P450 activity. ALDH1A1 expression can be detected in canals of Hering and bile duct epithelial cells and is increased on liver injury. Finally, we showed that the isolation and differentiation toward hepatocyte-like cells of LPCs with high ALDH activity is also successfully applicable to human liver samples. CONCLUSION: High ALDH activity is a feature of LPCs that can be taken advantage of to isolate these cells from untreated mouse as well as human liver tissues. This novel protocol is practically relevant, because it provides an easy and nontoxic method to isolate liver stem cells from normal tissue for potential therapeutic purposes.

"Cirrhosis" is a morphologic term that has been used for almost 200 years to denote the end stage of a variety of chronic liver diseases. The term implies a condition with adverse prognosis due to the well-known complications of portal hypertension, hepatocellular carcinoma, and liver failure. However, recent advances in the diagnosis and treatment of chronic liver diseases have changed the natural history of cirrhosis significantly. This consensus document by the International Liver Pathology Study Group challenges the usefulness of the word cirrhosis in modern medicine and suggests that this is an appropriate time to consider discontinuing the use of this term. The role of pathologists should evolve to the diagnosis of advanced stage of chronic liver disease, with emphasis on etiology, grade of activity, features suggestive of progression or regression, presence of other diseases, and risk factors for malignancy, within the perspective of an integrated clinicopathologic assessment.

Interest in hepatic ductular reactions (DRs) has risen in recent years because of a greater appreciation of their potential roles in regeneration, fibrogenesis, and carcinogenesis. However, confusion exists because there is significant, but often unappreciated diversity at the tissue, cellular, and subcellular levels in DRs of different diseases and stages of disease. DRs are encountered in virtually all liver disorders in which there is organ-wide liver damage and cell loss, but are also present in focal lesions such as focal nodular hyperplasia and adenoma. Moreover, diverse DR phenotypes can be present within any single disease entity, and are shaped by the etiology and evolution of the disease. Although much remains to be clarified, recent studies suggest that the diversity of appearances of the DRs are likely to reflect the differing signals at the anatomic, cellular, and molecular levels driving the proliferative response. These appear to determine the relative proportions of transit-amplifying cells, the degree of hepatocytic or cholangiocytic differentiation, and their relationships with stromal, vascular, and inflammatory components. The molecular signaling pathways governing these regenerative fate decisions closely replicate those found in human and other vertebrate embryos and more generally in stem cell niches throughout the body. Like the latter, complex interactions with matrix as well as mesenchymal and inflammatory cells, vessels, and innervation are likely to be of fundamental importance. Embracing systems/tissue biological approaches to exploring DRs, in addition to more traditional cellular and molecular biological techniques, will further enhance our understanding and, thereby, we believe potentiate new therapeutic possibilities.

Context.-Knowledge of the etiology and pathogenesis of chronic viral hepatitis has grown immensely during the past 50 years. The terminology used to assess liver biopsies with chronic viral hepatitis and the role of the liver biopsy itself have also evolved during this time. Although the focus of much discussion regarding diagnostic assessment of liver biopsies in patients with viral hepatitis has been on grading of activity and staging of fibrosis, each biopsy is also an opportunity to assess many other important features. Objectives.-To discuss opportunities provided by biopsies to assess features such as the presence of virus-associated premalignant or malignancy-related changes, and the presence of other concomitant diseases, including fatty liver disease of diverse causes, and hemochromatosis, hereditary or otherwise. Data Sources.-The data were obtained from published literature and professional experience. Conclusions.-The evaluation of liver biopsies with chronic viral hepatitis has evolved beyond grading and staging. Pathologists need to be aware of the other features that may have important clinical implications

A 48 year-old African American woman presented to her physician complaining of a rapidly evolving epigastric and right upper quadrant abdominal pain. A PET-CT of the abdomen and pelvis demonstrated hypermetabolic, polypoid masses within the gallbladder and several tumors in the left lobe of the liver for which she underwent diagnostic laparoscopy. The gallbladder revealed a 3.5 x 3.3 x 2.4 tan-brown exophytic mass located at the fundus and growing into the lumen with multiple contiguous papillary projections arising from the mucosal surface. A concurrent large cell neuroendocrine carcinoma and papillary adenocarcinoma of the gallbladder was revealed histologically. There was shared reactivity to antibodies directed against the distinct antigens for each morphological component with transitional tumor cells (of both histological components) located at the areas where the two tumor types merged, revealing common immunoreactivity for carcinoembryonic antigen, cancer antigen 19-9, keratin 19, c-kit (cluster of differentiation protein 117 (CD117)) and epithelial cell adhesion molecule. Ultrastructurally, individual cells were demonstrated to have overlapping features of neuroendocrine and glandular differentiation. The aforementioned histological, ultrastructural and immunohistochemical profile is strongly suggestive of a biphenotypic stem/progenitor cell tumor of the gallbladder.

Epithelial cell adhesion molecule (EpCAM) is a surface marker on human hepatic stem/progenitor cells that is reported as absent on mature hepatocytes. However, it has also been noted that in cirrhotic livers of diverse causes, many hepatocytes have EpCAM surface expression; this may represent aberrant EpCAM expression in injured hepatocytes or, as we now hypothesize, persistence of EpCAM in hepatocytes that have recently derived from hepatobiliary progenitors. To evaluate this concept, we investigated patterns of EpCAM expression in hepatobiliary cell compartments of liver biopsy specimens from patients with all stages of chronic hepatitis B and C, studying proliferation, senescence and telomere lengths. We found that EpCAM(+) hepatocytes were rare in early stages of disease, became increasingly prominent in later stages in parallel with the emergence of ductular reactions, and were consistently arrayed around the periphery of cords of keratin 19(+) hepatobiliary cells of the ductular reaction, with which they shared EpCAM expression. Proliferating cell nuclear antigen (proliferation marker) and p21 (senescence marker) were both higher in hepatocytes in cirrhosis than in normal livers, but ductular reaction hepatobiliary cells had the highest proliferation rate, in keeping with being stem/progenitor cell-derived transit amplifying cells. Telomere lengths in EpCAM(+) hepatocytes in cirrhosis were higher than EpCAM(-) hepatocytes (P < 0.046), and relatively shorter than those in the corresponding ductular reaction hepatobiliary cells (P = 0.057). CONCLUSION: These morphologic, topographic, immunophenotypic, and molecular data support the concept that EpCAM(+) hepatocytes in chronic viral hepatitis are recent progeny of the hepatobiliary stem/progenitor cell compartment through intermediates of the transit amplifying, ductular reaction hepatobiliary cells.