["The Journal of Physiology, Volume 604, Issue 7, Page 3135-3158, 1 April 2026. ", "\nAbstract figure legend In gravid human uterus smooth muscle, the oxytocin receptor (OXTR) and transient receptor potential vanilloid 4 (TRPV4) calcium channel colocalize at <40 nm by proximity ligation. TRPV4 is necessary for oxytocin‐induced calcium influx and contractility in uterine smooth muscle cells. However, direct TRPV4 agonism induces calcium influx and contractility in an OXTR‐independent manner. In uterine atony, OXTR‐TRPV4 spatial proximity is decreased. These findings further our understanding of physiological uterine contractility and the pathophysiology of postpartum haemorrhage from uterine atony. \n\n\n\n\n\n\n\n\n\nAbstract\nUnderstanding the mechanism of oxytocin‐induced uterine contractility is critical for addressing conditions at both extremes of the uterine contractility spectrum, preterm labour and uterine atony. We hypothesized that oxytocin induces extracellular calcium influx and uterine contraction through activation of the transient receptor potential vanilloid 4 (TRPV4) channel. To test this hypothesis, uterine tissue was obtained with informed consent from pregnant patients undergoing term, non‐labouring caesarean delivery. In human myometrial tissue and smooth muscle cells in primary culture (mSMCs), TRPV4 and oxytocin receptor (OXTR) proteins colocalize at distances less than 40 nm. In mSMCs, both pharmacological blockade of TRPV4 and TRPV4 depletion via small interfering RNA prevent oxytocin‐induced calcium influx and contraction. In contrast, voltage‐gated calcium channel blockade does not diminish oxytocin‐induced calcium transients. Pharmacological blockade of OXTR has no effect on TRPV4 agonist‐induced calcium influx or contractility. In uterine tissue from patients with oxytocin‐resistant uterine atony, there is a marked reduction in glycosylated OXTR expression and in proximity ligation between OXTR and TRPV4 compared with tissue from control patients with optimal postpartum contractility. Taken together, these findings demonstrate that in the gravid uterine smooth muscle, TRPV4 activation is required for oxytocin‐induced uterine contraction. They also suggest reduced OXTR–TRPV4 protein–protein interaction as a novel pathophysiological mechanism underlying uterine atony in non‐labouring parturients. These findings highlight the physiological importance of oxytocin signalling via the TRPV4 channel and may motivate the development of targeted, TRPV4‐focused treatments to modulate uterine contractility.\n\n\n\n\n\n\n\n\n\nKey points\n\nOxytocin‐induced contraction in smooth muscle cells from term pregnant human myometrium requires activation of the TRPV4 calcium channel.\nTRPV4 and oxytocin receptor (OXTR) colocalize at <40 nM and interact functionally in myometrial smooth muscle cells.\nTRPV4 antagonism or siRNA‐mediated TRPV4 knockdown abolishes oxytocin‐induced calcium influx and contractility.\nIn patients with oxytocin‐resistant uterine atony, glycosylated OXTR quantity and TRPV4–OXTR colocalization are markedly reduced.\nThese findings identify TRPV4 as a critical mediator of uterine contractility.\nTRPV4 antagonists may have a role as novel therapeutic agents for preventing or treating preterm labour.\n\n\n"]