THE STUDY OF HUMAN HEPATOCYTE GROWTH FACTOR IN VARIOUS LIVER DISEASES

Abstract

Hepatocyte growth factor represents a pleotropic cytokine with mito-, morpho- and moto-genic capacity for epithelial cells, angiogenic effects on endothelial cells, neurotropic for nerve cells and in a high concentration cytotoxic for some tumour cell lines.

By structural means HGF is a novel type of cytokine, in its processed state composed of a large alpha chain and a shorter beta chain. All known HGF effects are mediated via a transmembrane tyrosine kinase the c-mel proto-oncogene.

In this work, the expressions of HGF and its receptor c-met have been studied in normal and cirrhotic human liver tissues as well as the value of serum HGF levels in patients with chronic liver diseases in order to clarifY its clinical significance.

Initial screening with RT/PCR demonstrated that both HGF and c-mel mRNAs were expressed in normal and cirrhotic human liver tissues. The transcripts were also demonstrated by Northern blot analysis. Hybridisation of total RNA showed the 6 kb full length HGF transcript and the 7 kb c-met transcript in normal and cirrhotic human liver tissues. Hybridisation of poly (A)' RNA showed that beside the 6 kb full size HGF transcript, there was also a small amount of the alternatively spliced 1.5 kb transcript which codes for inactive truncated p28 protein.

In situ hybridisation analysis of normal human liver tissues showed that only some sinusoidal cells were expressing HGF mRNA, while the other sinusoidal and parenchymal cells were negative and the expression pattern was highly similar to those observed in the normal rat liver. In cirrhotic human liver tissues, in situ hybridisation of HGF and c-met mRNAs revealed a heterogeneous, overall reduced expression ofHGF in these tissues, while c-met transcripts were evenly distributed over the parenchymal liver cells and the fibrous septations were negative. It has been demonstrated also elevated HGF expression in areas of active inflammation .

HGF protein was detected immunologically by using Western immuno-blot after immunoprecipitation of HGF in protein extracts from either normal or cirrhotic liver tissues using a monoclonal antibody that detected only the alpha chain of HGF.