ACTA1 and metabolic dysfunction-associated steatohepatitis: Because human NASH progression correlates strongly with the extent of the ductular reaction (37), we performed immunostainings for markers of the ductular reaction (CK19) and hepatic stellate cell activation (α-SMA), which revealed that both ductular reaction and hepatic stellate cell activation were promoted by dietary fat in a dose-dependent fashion (Fig. 4D).