Background <p>Elevated intravesical pressure has been implicated as a key trigger in the onset and progression of bladder outlet obstruction (BOO)-induced inflammation and fibrosis. Mechanosensitive ion channel Piezo1 is abundantly expressed in urothelium. However, it remains unclear whether Piezo1 in the bladder epithelium is necessary for BOO-induced fibrosis. This study aimed to elucidate the role of urothelial Piezo1 in BOO-induced bladder fibrosis.</p> Methods <p>BOO was induced in female mice via partial urethral ligation. Urothelium-specific Piezo1 conditional knockout mice and Piezo1-knockout human urothelial cell line (SV-HUC-1) were used to investigate Piezo1 function in vivo and in vitro, respectively. Fibrosis was assessed using Masson’s trichrome staining and by evaluating protein expression levels of collagen I, fibronectin, and epithelial-to-mesenchymal transition (EMT) markers (α-SMA, N-cadherin, and E-cadherin).</p> Results <p>We observed that BOO was associated with mucosal fibrosis in both benign prostatic hyperplasia patients and BOO mice. Additionally, BOO induced upregulation of Piezo1, NLRP3 inflammasome, Caspase-1, IL-1β, and EMT markers (α-SMA, N-cadherin) in urothelial cells from both human and mouse. Notably, these changes were significantly attenuated in urothelial Piezo1-knockout mice. In vitro, pathological cyclic pressure stimulation (100 cmH₂O for 5 minutes every 2 hours over 24 hours) led to increased expression of NLRP3, Caspase-1, IL-1β, EMT markers, and profibrotic changes in SV-HUC-1 cells. These pressure-induced changes were markedly reduced in Piezo1-knockout cells. Mechanistically, Piezo1 activation under high pressure leads to several cellular events such as intracellular Ca^{2 +} increase, ATP release, ROS generation, and NF-κB activation, culminating in NLRP3 activation.</p> Conclusions <p>Our findings suggest that Piezo1 contributes to BOO induced inflammation and fibrosis, and targeting Piezo1 represent a novel strategy for treatment of bladder fibrosis.</p>