Thrombospondin-1 as a Mechanosensitive Matrix Protein Driving Fibroblast Senescence: A Novel Pathogenic Target for Pelvic Organ Prolapse.

INTRODUCTION AND HYPOTHESIS: Current pelvic organ prolapse (POP) management focuses on anatomical repair without addressing the underlying pathology. Fibroblast dysfunction underlies pelvic tissue degeneration, but its upstream regulation remains unclear. Here, we investigated whether a pro-senescent protein, thrombospondin-1 (THBS1), responds to stress injury and activates a cellular senescence-matrix degradation axis, offering a potential target for POP. METHODS: Machine learning identified mechanosensitive senescence-associated markers from transcriptional profiles of uterosacral ligament (USL) tissues of POP patients. Histology assessed extracellular matrix (ECM) composition, senescence phenotypes, and THBS1 expression. Primary USL fibroblasts isolated from POP patients were transfected with THBS1-specific RNA interference fragments and then evaluated for proliferation, senescence, and ECM synthesis. Complementary gain- and loss-of-function assays in RAT1 fibroblasts using recombinant human THBS1 (rhTHBS1) or THBS1 knockdown further delineated the role of THBS1 in cellular senescence, matrix degradation, and recovery from damage induced by mechanical stress or chemical insults (H2O2, Etoposide). RESULTS: THBS1 was identified as a mechanosensitive, senescence-associated matricellular protein in POP. Tissues and fibroblasts from POP patients showed increased expression of senescence markers and THBS1, accompanied by reduced expression of ECM components, compared to those of non-POP patients. Knockdown of THBS1 enhanced proliferative capacity and ameliorated senescent phenotypes in POP patient-derived fibroblasts. Moreover, exogenous rhTHBS1 promoted senescence and matrix degradation in RAT1 cells, whereas THBS1 knockdown rescued the cellular damage induced by mechanical or chemical stress. CONCLUSIONS: THBS1 mediates stress-induced pelvic floor degeneration by promoting fibroblast senescence and disrupting ECM homeostasis, highlighting its potential as a promising target for POP.