Immunohistochemical evaluation of hepatic progenitor cells in different types of feline liver diseases

Abstract

Hepatic progenitor cells are periportally resident cells capable of differentiating into mature hepatocytes or cholangiocytes to ensure hepatic regeneration. This reaction is termed a ductular reaction. In the present study, regenerative response of the feline liver to different hepatic diseases was investigated immunohistochemically. Regeneration of the liver through hepatocellular replication and proliferation of progenitor cell compartment were comparatively evaluated. Histological and immunohistochemical stainings were conducted on feline liver samples (n=40) representing various hepatobiliary diseases. Cytokeratin (CK) 7, CK19, Proliferating cell nuclear antigen (PCNA), Ki67, and Human hepatocyte marker 1 (Hep Par-1) were used. The presence of progenitor cells within feline livers was proved, both as passive cells in normal liver and as active cells (ductular reaction) in hepatic lesions. CK7 was found to be a suitable antibody for immunohistochemically detecting feline progenitor cells. In acute events, regeneration was predominantly shaped by the division of hepatocytes. In chronic events and severe acute events, hepatocytes lost their ability to divide and regeneration mainly occurred through progenitor cells. Location of the ductular reaction varied between different hepatic diseases. Parenchymal ductular reaction was detected in fulminant hepatitis, chronic hepatitis, hepatocellular lipidosis and metastatic lymphoma, whereas septal ductular reaction was detected in chronic hepatitis and metastatic lymphoma. Ductular reaction exhibited positive staining for Hep Par-1 in chronic and severe acute events. This study indicates the major role played by hepatic progenitor cells in regeneration of the feline liver. Moreover, it shows how the activation pattern of ductular reaction varies according to the hepatobiliary disease type.

Keywords: ductular reaction; feline; hepatic progenitor cell; immunohistochemistry; regeneration.

Fig. 1.

Cytokeratin (CK) 7 staining in different feline specimens, Cat. A: Mild CK7 positive portal ductular reaction (arrow), passive congestion. B: Prominent CK7 portal and periportal ductular reaction (arrows), fulminant hepatitis. C: Portal, periportal (black arrow) and septal (white arrow) CK7 positive progenitor cells, metastatic lymphoma. D: Portal and periportal ductular reaction surrounding the periductular lymphocytic infiltration (arrows), lymphocytic cholangiohepatitis. E: Portal, periportal (arrows) and parenchymal (arrowhead) CK7 positive ductular reaction, hepatocellular lipidosis. F: CK7 positive ductular reaction embedded in the septal fibrotic structures (white arrow), congenital cystic disease. Bars= 50 μm (A–E), 20 μm (F).

Fig. 2.

The different morphological components of ductular reaction, Cat. A: Clusters (arrow) and solitary single oval shaped cells (arrowhead) with strong cytoplasmic staining located in the parenchyma. B: Intermediate cell (arrow) or hepatocyte resembling cell featuring membranous CK7 staining. C: Clusters of progenitor cells radiating into the parenchyma (arrow). D: Small ductules without lumen (arrow) and solitary progenitor cells (arrowhead) mainly periportal.

Fig. 3.

Proliferating cell nuclear antigen (PCNA) staining in different feline specimens, Cat. A: Prominent PCNA staining of centrilobular hepatocytes (arrows), passive congestion. B: Low hepatocellular PCNA positivity (arrows), fulminant hepatitis. C: Absence of PCNA positive hepatocytes in the adjacent parenchyma (star) with prominent positivity of metastatic lymphoid tumor cells, metastatic lymphoma. D: Periportal hepatocellular PCNA positivity (arrows), lymphocytic cholangiohepatitis.

Fig. 4.

Human hepatocyte marker 1 (Hep Par-1) staining in various feline specimens, Cat. A: Degenerative hepatocytes shows a mild Hep Par-1 positivity compared to the surrounding mature hepatocytes showing prominent positive staining, hepatocellular lipidosis. B: Negative staining of the majority of the portal ductular structures (arrow), hepatocellular lipidosis. C: Positively staining epithelial cells of the ductular reaction with Hep Par-1. Reactive ductules (arrow), single and clusters of progenitor cells (arrowheads) portally located, fulminant hepatitis. D: Septal ductular reaction strongly reacting with Hep Par-1. Slight granular (arrowhead) and intensive (arrow) cytoplasmic positive progenitor cells, metastatic lymphoma.