β-catenin initiates peritoneal fibrosis by triggering mitochondrial fission-mediated mesothelial cell senescence fate transition

Background: Peritoneal fibrosis represents a major clinical challenge for end-stage renal disease (ESRD) patients when they are undergoing peritoneal dialysis (PD). Single-cell RNA sequencing identified that peritoneal mesothelial cells undergo a senescence fate transition in long-term PD patients. Whereas the existence of mesothelial cell senescence and the underlying mechanisms should be thoroughly explored. Methods: To further investigate mesothelial cell senescence, we utilized a clinical cohort comprising dialysate effluents from PD patients and peritoneal biopsy specimens, peritoneal dialysis fluid (PDF)-induced mouse models, and cultured primary mesothelial cells. Single-cell RNA sequencing, transcriptome sequencing, immunofluorescence, Western blotting, and other analyses were administered. To validate the critical role of β-catenin in mesothelial cell senescence, β-catenin knockout mice were employed. Additionally, the senolytic drugs dasatinib plus quercetin were administered to PDF mice to assess the key role of mesothelial cell senescence in peritoneal fibrosis. Results: Single-cell RNA sequencing demonstrated that mesothelial cells derived from long-term PD patients are major trend to senescence fate. Moreover, β-catenin signaling was significantly upregulated, as well as transforming growth factor-β (TGF-β) pathways. We observed that senescent mesothelial cells were highly increased in both dialysate effluent and peritoneal biopsies of long-term PD patients. In dialysate effluent, matrix metalloproteinase-7 (MMP-7), an indicator of downstream targets of β-catenin, was positively correlated with TGF-β1. Both biomarkers were also positively associated with PD duration. Mechanistically, we found that β-catenin promotes dynamin-related protein 1 (Drp1) expression, a key mediator of mitochondrial fission, thereby inducing mesothelial cell senescence. Then, TGF-β1 was secreted to activate the Smad signaling pathway in fibroblasts, leading to myofibroblast activation and subsequent peritoneal fibrosis. Notably, administration of senolytic drugs, dasatinib plus quercetin, significantly alleviated peritoneal fibrosis regardless of treatment timing. Conclusion: Targeting β-catenin signaling and mesothelial cell senescence may represent potential therapeutic interventions for preventing peritoneal fibrosis.