Effect of depletion of TSPAN6 on Biliary Epithelial Cells with and without LPS stimulation mirroring liver disease.
A unique pathological hallmark of chronic liver disease (CLD) is the ductular reaction, characterised by the proliferation of reactive bile ducts associated with an inflammatory infiltrate.  In this study we identify the Tetraspanin family member, TSPAN6, as a novel regulator of biliary-immune cell cross talk.  We initially demonstrate that TSPAN6 is expressed by biliary ductules within the ductular reaction from samples of cirrhotic human liver tissue across multiple aetiologies and significantly elevated in cholestatic liver diseases.  We also confirm that it is upregulated in in vivo models of ductular reaction.  Additionally, TSPAN6 protein expression demonstrated a positive correlation with the presence of infiltrating (MAC387+) macrophages.  Using a human in vitro model of primary biliary epithelial cell (BEC)-monocyte cross talk, we demonstrate that TSPAN6 regulates BEC-driven monocyte activation and chemokine production.   Specifically, LPS stimulation of BEC led to downstream inflammatory activation of human monocytes, with upregulation of pro-inflammatory chemokines.  TSPAN6 knockdown in BEC partially reversed this in monocyte activation, with specific reduction in the chemokines CXCL1,2 and 5. Transcriptomic profiling, following TSPAN6 depletion, confirmed its involvement in membrane-associated trafficking and lipid modification pathways in biliary epithelial cells.  We propose TSPAN6 as a potential organiser of epithelial signalling platforms, contributing to inflammation and regeneration, during liver injury and could therefore be a novel therapeutic target in CLD. Overall design: RNA-seq profiling of Biliary Epithelial Cells after TSPAN6 depletion in LPS and untreated cell types.