Fibrotic Scarring Screening - Zebrafish Phenotype Assay
Fish swim against water current to spawn, feed and to stay within a particular habitat. This natural motion against water current is termed as positive rheotaxis.
Diet induced NASH zebrafish model exhibits compromised rheotaxis, while wild type control larvae exhibit normal rheotaxis.
“Drugs that rescue fibrotic scarring can be identified by rheotaxis phenotype rescue”
The following key pathological events are observed in NASH progressing zebrafish larvae with fibrotic scarring
Extracellular matrix (ECM) in chronically injured liver
NASH Larvae with poor rheotaxis exhibits lower MMP-1 and higher MMP-2 in the liver, a similar pattern as seen in fibrotic livers. The model also exhibits an increase in TIMP expression levels and increase in collagen deposits indicating similar molecule events as in NASH pathology.
Activation of hepatic stellate cells
NASH Larvae show severe pattern of myofibroblastic cells in the liver, cells that are differentiated from hepatic stellate cells - indicating progress of fibrosis. Hepatic scoring indicates a late-stage score of 5/5.
Mediators of hepatocellular damage
NASH larvae show a continues and heightened activation of gene expression pathways across the PDGF and VEGF axis. This confirms that mediators of hepatocellular damage in zebrafish follow similar downstream pathways of cellular signaling that drive the fibrosis pathology.
Validated comparators that showed rescue in Zebrafish Rheotaxis Assay
Aldosterone receptor antagonist and SCD1 inhibitors have shown rescue in recent phenotype screens.