Understanding the mechanisms regulating liver fibrosis (including the use of imaging techniques in its study and diagnosis)

Abstract

Fibrosis is characterised by the excessive accumulation of extracellular matrix (ECM) proteins, resulting in a loss of tissue architecture and function. Central in liver fibrosis development is the transdifferentiation of hepatic stellate cells (HSCs) to a myofibroblast phenotype, responsible for increased deposition of ECM. Presently there are no treatments available for fibrosis. Critical to the discovery of novel anti-fibrotics is the development of a non-invasive imaging modality to accurately diagnose fibrosis severity. The hepatic myofibroblast specific single chain antibody (scAb) C1-3 was conjugated with a fluorophore and administered to mice with liver fibrosis prior to IVIS imaging to diagnose fibrosis severity. The expression of C1-3’s target antigen (synaptophysin) was confirmed by quantitative real-time PCR (qRT-PCR) and immunocytochemistry (ICC) in both quiescent and activated HSCs. The anti-inflammatory effects of PXR agonists were investigated utilising an in vivo model of liver fibrosis. Finally the pro-inflammatory properties of hepatic myofibroblasts were studied in vitro and in vivo. There was a statistically significant increase in fluorescence detected ex vivo in fibrotic livers versus the controls. qRT-PCR confirmed that quiescent HSCs (qHSCs) and hepatic myofibroblasts express similar levels of synaptophysin. The PXR agonist PCN significantly reduced the level of liver inflammation (NF-κB activity) following liver injury in vivo, 24 hours after its administration. The data presented indicates hepatic myofibroblasts release a pro-inflammatory soluble factor and induce NF-κB activity when injected in vivo. These findings suggest that hepatic myofibroblast number is an indicator of fibrosis severity. Hepatic myofibroblasts possess pro-inflammatory characteristics, which may contribute to fibrosis development. Finally PXR agonists exhibited anti-inflammatory properties that may be beneficial in the treatment of liver fibrosis.