Abstract
Toxicant exposure can lead to acute liver injury, characterized by hepatic reprogramming and wound healing. Hepatic stellate cells (HSC) play a key role in liver regeneration during wound healing by secreting fibrogenic factors and production of extracellular matrix (ECM). However, repetitive injury to the liver can lead to extensive scarring and liver fibrosis, indicating HSCs coordinate both regeneration and disease. Because the factors contributing to HSC reprogramming during wound healing are not fully defined, we sought to further characterize morphogenic pathways of regeneration in an acute model of toxicant-induced liver injury1. Wnt/β-catenin signaling has been recently associated with progressive liver fibrosis, but its role in HSC reprogramming is not well defined. Here, we investigated the canonical role of Wnt3a/Wnt5a on β-catenin-dependent HSC transdifferentiation and find that hepatic ECM gene expression is increased and associated with Wnt3a, Wnt5a, and their transducers (Frizzled-2 and Frizzled-7) after an acute exposure of the hepatotoxin, carbon tetrachloride(CCl4). Moreover, we find exogenous Wnt3a and Wnt5a can accelerate spontaneous, culture-induced HSC activation in vitro as evidenced by increased total expression of fibrogenic factors, including Col1a1 and α-SMA. Challenge with Wnt3a induced canonical β-catenin-dependent transcription of axin2, which was attenuated by the Wnt coreceptor antagonist, Dickkopf-1 (DKK-1). These data support a role for canonical Wnt signaling as an additional mechanism by which HSCs dynamically respond to liver injury during the early wound healing response. New & noteworthy. This study elucidates novel mechanisms of fibrotic gene reprogramming in the liver. Specifically, we describe that Wnts and their transducers are increased during early liver injury which are associated with early fibrogenic responses and for the first time, causally link Wnts as direct inducers of HSC activation in the liver.