YAP activation in liver macrophages via depletion of MST1/MST2 enhances liver inflammation and fibrosis in MASLD

Abstract Macrophages have been recognized as pivotal players in the progression of MASLD/MASH. However, the molecular mechanisms underlying their multifaceted functions in the disease remain to be further clarified. In the current study, we developed a new mouse model with YAP activation in macrophages to delineate the effect and mechanism of YAP signaling in the pathogenesis of MASLD/MASH. Genetically modified mice, featuring specific depletion of both Mst1 and Mst2 in macrophages/monocytes, were generated and exposed to a high‐fat diet for 12 weeks to induce MASLD. Following this period, livers were collected for histopathological examination, and liver non‐parenchymal cells were isolated and subjected to various analyses, including single‐cell RNA‐sequencing, immunofluorescence and immunoblotting and qRT‐PCR to investigate the impact of YAP signaling on the progression of MASLD. Our data revealed that Mst1/2 depletion in liver macrophages enhanced liver inflammation and fibrosis in MASLD. Using single‐cell RNA‐sequencing, we showed that YAP activation via Mst1/2 depletion upregulated the expressions of both pro‐inflammatory genes and genes associated with resolution/tissue repair. We observed that YAP activation increases Kupffer cell populations (i.e., Kupffer‐2 and Kupffer‐3) which are importantly implicated in the pathogenesis of MASLD/MASH. Our data indicate that YAP activation via Mst1/2 deletion enhances both the pro‐inflammatory and tissue repairing functions of Kupffer‐1 and ‐2 cells at least in part through C1q. These YAP‐regulatory mechanisms control the plasticity of liver macrophages in the context of MASLD/MASH. Our findings provide important evidence supporting the critical regulatory role of YAP signaling in liver macrophage plasticity and the progression of MASLD. Therefore, targeting the Hippo‐YAP pathway may present a promising therapeutic strategy for the treatment of MASH.