Quantitative morphometric and immunohistochemical analysis and their correlates in cirrhosis--A study on explant livers

The role of neutrophils in triptolide-induced liver injury

Triptolide (TP) induces severe liver injury, but its hepatotoxicity mechanisms are still unclear. Inflammatory responses may be involved in the pathophysiology. Neutrophils are the first-line immune effectors for sterile and non-sterile inflammatory responses. Thus, the aim of the present study was to investigate the neutrophilic inflammatory response in TP-induced liver injury in C57BL/6 mice. Our results showed that neutrophils were recruited and accumulated in the liver, which was parallel to or slightly after the development of liver injury. Neutrophils induced release of myeloperoxidase and up-regulation of CD11b, which caused cytotoxicity and hepatocyte death. Hepatic expressions of CXL1, TNF-α, IL-6, and MCP1 were increased significantly to regulate neutrophils recruitment and activation. Up-regulation of toll like receptors 4 and 9 also facilitated neutrophils infiltration. Moreover, neutrophils depletion using an anti-Gr1 antibody showed mild protection against TP overdose. These results indicated that neutrophils accumulation might be the secondary response, not the cause of TP-induced liver injury. In conclusion, the inflammatory response including neutrophil infiltration may play a role in TP-induced hepatotoxicity, but may not be severe enough to cause additional liver injury.

Ductular reaction correlates with fibrogenesis but does not contribute to liver regeneration in experimental fibrosis models

Background and aims

Ductular reaction is a standard component of fibrotic liver tissue but its function is largely unknown. It is supposed to interact with the matrix producing myofibroblasts and compensate the declining regenerative capacity of hepatocytes. The relationship between the extent of fibrosis—ductular reaction, proliferative activity of hepatocytes and ductular reaction were studied sequentially in experimental hepatic fibrosis models.

Methods

Liver fibrosis/cirrhosis was induced in wild type and TGFβ overproducing transgenic mice by carbon tetrachloride and thioacetamide administration. The effect of thioacetamide was modulated by treatment with imatinib and erlotinib. The extent of ductular reaction and fibrosis was measured by morphometry following cytokeratin 19 immunofluorescent labeling and Picro Sirius staining respectively. The proliferative activity of hepatocytes and ductular reaction was evaluated by BrdU incorporation. The temporal distribution of the parameters was followed and compared within and between different experimental groups.

Results

There was a strong significant correlation between the extent of fibrosis and ductular reaction in each experimental group. Although imatinib and erlotinib temporarily decreased fibrosis this effect later disappeared. We could not observe negative correlation between the proliferation of hepatocytes and ductular reaction in any of the investigated models.

Conclusions

The stringent connection between ductular reaction and fibrosis, which cannot be influenced by any of our treatment regimens, suggests that there is a close mutual interaction between them instead of a unidirectional causal relationship. Our results confirm a close connection between DR and fibrogenesis. However, since the two parameters changed together we could not establish a causal relationship and were unable to reveal which was the primary event. The lack of inverse correlation between the proliferation of hepatocytes and ductular reaction questions that ductular reaction can compensate for the failing regenerative activity of hepatocytes. No evidences support the persistent antifibrotic property of imatinib or erlotinib.

Human liver regeneration in advanced cirrhosis is organized by the portal tree

BACKGROUND & AIMS

In advanced cirrhosis new hepatocytic nodules are generated by budding of ductules in areas of parenchymal extinction. However, the vascular alterations in the areas of parenchymal extinction, the blood supply and the structure of the new hepatocytic nodules have not been analyzed in detail.

METHODS

Explanted human cirrhotic livers of three different etiologies and two experimental rat models of cirrhosis were thoroughly examined. 3D reconstruction of the immunohistochemically stained serial sections and casting of human and experimental cirrhotic livers have been used to reveal the structural organization of the regenerative buds.

RESULTS

In areas of parenchymal extinction the skeleton of the liver, the portal tree is preserved. The developing regenerative nodules are positioned along the portal tree and are directly supplied by terminal portal venules. The expanding nodules grow along the trunks of the portal vein. Casting of human and experimental cirrhotic livers by colored resin confirms that nodules are supplied by portal blood. The two other members of the portal triads become separated from the portal veins.

CONCLUSIONS

As the structure of the hepatocyte nodules (centrally located portal vein branches, bile ducts at the periphery, hepatic veins and arteries in the connective tissue) impedes the restoration of normal liver structure, the basic architecture of hepatic tissue suffers permanent damage. We suggest that "budding" may initiate the second, irreversible stage of cirrhosis.

LAY SUMMARY

Cirrhosis is the final common outcome of long lasting hepatic injury defined as the destruction of the normal liver architecture by scar tissue. In the late phase of cirrhosis stem cells-derived hepatocyte nodules appear along the branches of the portal vein suggesting an important role of this specially composed blood vessels (containing digestive end-products from the stomach and intestines) in liver regeneration. Our results contribute to a better understanding of this serious liver disease.