Interleukin-33-Dependent Innate Lymphoid Cells Mediate Hepatic Fibrosis

• IL-33 expression is upregulated in human and murine hepatic fibrosis
• IL-33 release due to hepatocellular stress induces severe hepatic fibrosis in vivo
• IL-33 expands liver resident innate lymphoid cells
• IL-13 from ILC2 drives liver tissue remodeling by hepatic stellate cell activation

SummaryLiver fibrosis is a consequence of chronic liver diseases and thus a major cause of mortality and morbidity. Clinical evidence and animal studies suggest that local tissue homeostasis is disturbed due to immunological responses to chronic hepatocellular stress. Poorly defined stress-associated inflammatory networks are thought to mediate gradual accumulation of extracellular-matrix components, ultimately leading to fibrosis and liver failure. Here we have reported that hepatic expression of interleukin-33 (IL-33) was both required and sufficient for severe hepatic fibrosis in vivo. We have demonstrated that IL-33’s profibrotic effects related to activation and expansion of liver resident innate lymphoid cells (ILC2). We identified ILC2-derived IL-13, acting through type-II IL-4 receptor-dependent signaling via the transcription factor STAT6 and hepatic stellate-cell activation, as a critical downstream cytokine of IL-33-dependent pathologic tissue remodeling and fibrosis. Our data reveal key immunological networks implicated in hepatic fibrosis and support the concept of modulation of IL-33 bioactivity for therapeutic purposes.

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