Role of HGF/SF in tissue regeneration

Nonalcoholic fatty liver disease (NAFLD), and the more advanced stage nonalcoholic steatohepatitis (NASH), is nowadays a major health problem with a global prevalence estimated at 25%. NAFLD patients have an increased risk to develop cirrhosis, end stage liver disease, and hepatocellular carcinoma. While there is an urgent need for effective treatment, unfortunately, there are no approved drugs for this condition. Hepatocyte apoptosis and inflammatory response are key events for NASH development. It was therefore hypothesized that combination therapy with Hepatocyte Growth Factor/Scatter Factor (HGF/SF), the most potent liver survival-promoting factor, and a macrophage-focused immunotherapeutic drug able to switch M1 macrophages to M2 phenotype can cure NASH. Unfortunately, HGF/SF is unsuitable for therapy because it has a limited tissue/organ penetration and distribution due to its high affinity for heparan sulphate proteoglycans (HSPG). Moreover, it has a short half-life and is unstable in physiological buffers. Therefore, our laboratory in collaboration with the group of Dr. Vicogne at Pasteur Institute in Lille designed and produced K1K1, a new engineered fragment of HGF/SF able to overcome the limitations of the parent molecule and to be more suitable as a drug candidate. The stability and the biological activity of K1K1 were compared to HGF/SF, highlighting K1K1 superiority. Furthermore, we investigated the activation of signaling pathways in two liver cell lines after stimulation with K1K1, HGF/SF, and other recombinant proteins, showing that K1K1 was as good as HGF/SF. In order for K1K1 treatment to work, it was important to confirm that the receptor is present, and the pathway is relevant in the diseased tissue. Assessment of MET protein expression with immunohistochemistry (IHC) in formalin-fixed paraffin-embedded (FFPE) liver samples of patients with NAFLD showed that MET receptor is expressed on the hepatocytes and therefore K1K1 could be regarded a good drug candidate for use in future therapy. Finally, we have evaluated the protective effect of K1K1 alone or in combination with macrophage-focused immunotherapeutic drugs on a NASH-on-a-chip model. The combination therapy was found to be the most effective in reducing steatosis, apoptosis, and fibrosis. These promising results highlight K1K1 potential as a new drug candidate for NASH treatment.