Longitudinal Study of the Pathomechanisms of Fibrogenesis/cirrhosis and Growth and Regenerationin Copper Storage Disease

Hepatic fibrosis/cirrhosis results from chronic liver injury during which hepatic stellate cells (HSC) proliferate and differentiate into matrix-producing cells. Liver progenitor cell (LPC) activation is seen in the majority of chronic human liver diseases. LPCs seem to be able to survive when mature hepatocytes are lost due to toxic damage or viral infections. Long-time follow-up of individuals allows describing the involved pathomechanisms. COMMD1 deficiency results in copper toxicosis (CT). The precise role of this protein is not clear, but evidence suggests involvement in cellular trafficking, functioning of ATP7B and NF-kB and HIF-1α signalling. Five COMMD1 -/- dogs were used for longitudinal follow-up. Liver biopsies (each 6 months up to 42 months) were used for HE-staining, reticulin stain, rubeanic acid, immunohistochemistry for a-SMA, Ki67 and K19, Q-RTPCR on gene products involved in fibrogenesis and regeneration and Western Blotting for (non-)phosphorylated Smad2/3 and Stat3.
Time-dependent progressive fibrogenesis was indicated by increased a-SMA and reticulin staining. Increased HIF-1α mRNA expression was followed by increased mRNA expression of TFG-β1 and its receptors. However, the Smad2/3 pathway is not activated. During the progression of the hepatitis increased activity of CK19, but not Ki67 is seen. Although an increased mRNA expression of HGF and cMET is seen during a short period, the Stat3 pathway is increasingly activated during aging.
Conclusions: To our knowledge this is the first longitudinal study on fibrogenesis in a large animal model. Results indicated increased expression of TGF-β1 related genes and markers of activated HSCs. HIF-1α and the presence of activated HSCs can be used as early indicators of fibrogenesis and utilized as therapeutic targets. Liver regeneration in CT is mainly derived form the LPC compartment rather than from the adult hepatocyte. This dog model is useful for studying the initial and progressed stages of liver fibrosis and the evaluation of antifibrotic therapies.