A Spatial Atlas of Wnt Receptors in Adult Mouse Liver

Investigating the role of Wnt3a and Wnt5a as critical factors of hepatic stellate cell activation in acute toxicant-induced liver injury

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.

Design principles and therapeutic applications of novel synthetic WNT signaling agonists

Wingless-related integration site or Wingless and Int-1 or Wingless-Int (WNT) signaling is crucial for embryonic development, and adult tissue homeostasis and regeneration, through its essential roles in cell fate, patterning, and stem cell regulation. The biophysical characteristics of WNT ligands have hindered efforts to interrogate ligand activity in vivo and prevented their development as therapeutics. Recent breakthroughs have enabled the generation of synthetic WNT signaling molecules that possess characteristics of natural ligands and potently activate the pathway, while also providing distinct advantages for therapeutic development and manufacturing. This review provides a detailed discussion of the protein engineering of these molecular platforms for WNT signaling agonism. We discuss the importance of WNT signaling in several organs and share insights from the initial application of these new classes of molecules in vitro and in vivo. These molecules offer a unique opportunity to enhance our understanding of how WNT signaling agonism promotes tissue repair, enabling targeted development of tailored therapeutics.

Wnt/β-Catenin signaling pathway in hepatocellular carcinoma: pathogenic role and therapeutic target

Hepatocellular carcinoma (HCC) is the most common primary malignant liver tumor and one of the leading causes of cancer-related deaths worldwide. The Wnt/β-Catenin signaling pathway is a highly conserved pathway involved in several biological processes, including the improper regulation that leads to the tumorigenesis and progression of cancer. New studies have found that abnormal activation of the Wnt/β-Catenin signaling pathway is a major cause of HCC tumorigenesis, progression, and resistance to therapy. New perspectives and approaches to treating HCC will arise from understanding this pathway. This article offers a thorough analysis of the Wnt/β-Catenin signaling pathway's function and its therapeutic implications in HCC.

Compartmentalization, cooperation, and communication: The 3Cs of Hepatocyte zonation

The unique architecture of the liver allows for spatial compartmentalization of its functions, also known as liver zonation. In contrast to organelles and cells, this compartment is devoid of a surrounding membrane, rendering traditional biochemical tools ineffective for studying liver zonation. Recent advancements in tissue imaging and single-cell technologies have provided new insights into the complexity of tissue organization, rich cellular composition, and the gradients that shape zonation. Hepatocyte gene expression profiles and metabolic programs differ based on their location. Non-parenchymal cells further support hepatocytes from different zones through local secretion of factors that instruct hepatocyte activities. Collectively, these elements form a cohesive and dynamic network of cell-cell interactions that vary across space, time, and disease states. This review will examine the cell biology of hepatocytes in vivo, presenting the latest discoveries and emerging principles that govern tissue-level and sub-cellular compartmentalization.