Kupffer-cell-derived IL-6 is repurposed for hepatocyte dedifferentiation via activating progenitor genes from injury-specific enhancers.

Stem cell-independent reprogramming of differentiated cells has recently been identified as an important paradigm for repairing injured tissues. Following periportal injury, mature hepatocytes re-activate reprogramming/progenitor-related genes (RRGs) and dedifferentiate into liver progenitor-like cells (LPLCs) in both mice and humans, which contribute remarkably to regeneration. However, it remains unknown which and how external factors trigger hepatocyte reprogramming. Here, by employing single-cell transcriptional profiling and lineage-specific deletion tools, we uncovered that periportal-specific LPLC formation was initiated by regionally activated Kupffer cells but not peripheral monocyte-derived macrophages. Unexpectedly, using in vivo screening, the proinflammatory factor IL-6 was identified as the niche signal repurposed for RRG induction via STAT3 activation, which drove RRG expression through binding to their pre-accessible enhancers. Notably, RRGs were activated through injury-specific rather than liver embryogenesis-related enhancers. Collectively, these findings depict an injury-specific niche signal and the inflammation-mediated transcription in driving the conversion of hepatocytes into a progenitor phenotype.

A Homeostatic Arid1a-Dependent Permissive Chromatin State Licenses Hepatocyte Responsiveness to Liver-Injury-Associated YAP Signaling.

Following injury, differentiated epithelial cells can serve as a stem cell-independent source for tissue regeneration by undergoing reprogramming into other cell types. The intrinsic molecular basis underlying plasticity of differentiated cells remains largely unaddressed. Here we show that Arid1a, a key component of the SWI/SNF chromatin remodeling complex, controls liver regeneration and gene expression associated with emergence of injury-induced liver-progenitor-like cells (LPLCs). Hepatocyte-specific Arid1a ablation reduces LPLC gene expression in several models of periportal liver injury and impairs liver regeneration, leading to organ dysfunction. Arid1a establishes a permissive chromatin state at LPLC-enriched genes during homeostasis, suggesting it endows hepatocytes with competence to respond to injury-induced signals. Consistently, Arid1a facilitates binding of YAP, a critical regeneration signaling pathway, to LPLC-enriched genes, and Arid1a deletion prevents their YAP-associated induction following injury. Together, these findings provide a framework for studying the contributions of injury-induced LPLCs to periportal liver regeneration.