OBJECTIVESTo identify hepatic progenitor cells (HPCs) in patients with severe hepatitis (SH) by detecting their markers and investigate the features of their distribution and location.

METHODSLiver tissues taken from 59 SH patients were tested for the receptor of stem cell factor (c-kit), pi-class glutathione S-transferase (GST-pi), cluster of differentiation 34 (CD34), cytokeratin 19 (CK19), cytokeratin 18 (CK18) and alpha fetoprotein (AFP) by immunohistochemistry (IHC). Meanwhile, 58 patients with acute or chronic hepatitis were also detected to act as controls.

RESULTSHepatic progenitor cells could be seen in SH patients. Most of them existed as ductular cells that had been called "typical ductular proliferation (ADP)" or "typical ductular reaction" in previous research. These ductular cells were mainly located at the portal areas, fibro septa, periportal parenchyma and the border of the pseudolobuli and inflammatory foci. Further, c-kit, GST-pi, CK19 and CK18, but not CD34 and AFP could be detected in these cells. Another kind of HPC was the small hepatocyte-like cell (SHLC), which could express c-kit, GST-pi, and CK18, but not CK19, CD34 and AFP. The semi-quantitative analysis showed that the scope of ADP in SH patients was significantly larger than that in acute and chronic hepatitis patients (chi2= 63.62, P<0.05), and the scope of ADP in subacute severe hepatitis and chronic severe hepatitis patients was also significantly larger than that in acute severe hepatitis patients.

CONCLUSIONIn the course of regeneration of viral hepatitis, different types of pathology have different features. In acute and chronic hepatitis (G1-2), the regeneration is mainly owing to the proliferation of mature hepatocytes, and in chronic hepatitis (G3-4), there is the participation of HPCs, although they are limited. In severe hepatitis, however, since the replicative capacity of normal hepatocytes is impaired or prohibited, liver regenerates and restores mainly by the means of hepatic stem cells activation and proliferation. But the hepatic stem cells don't differentiate into their mature functional compartments directly at all. There are several intermediary or transition populations. In human severe hepatitis, they are mainly ductular cells, and parts of them are small hepatocyte-like cells.