Impaired PIEZO1 Function Drives Uterine Hypercontractility in Adenomyosis-Associated Dysmenorrhea

STUDY QUESTION Does PIEZO1 play any role in adenomyosis-associated dysmenorrhea? SUMMARY ANSWER PIEZO1 downregulation in the myometrium reduces the expression of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) production, leading to increased and irregular contractility that contributes to dysmenorrhea in women with adenomyosis. WHAT IS KNOWN ALREADY Aberrant uterine contractility has long been documented in women with adenomyosis, but our knowledge of the molecular mechanisms governing uterine contractility is quite limited. Oxytocin receptor (OTR) expression in myometrium is elevated and correlates with uterine contractile amplitude and the severity of dysmenorrhea in women with adenomyosis. Adenomyosis induced in mice led to increased uterine contractile amplitude and irregularity, accompanied by progressive generalized hyperalgesia. Additionally, increased myometrial vasopressin receptor (VP1αR) and potentially prostaglandin F2α (PGF2α) may also contribute to uterine hyperactivity. STUDY DESIGN, SIZE, AND DURATION After written informed consent, we collected myometrial tissues ipsilateral and contralateral to adenomyotic lesions from 30 patients with adenomyosis (AM). As controls, normal myometrial tissue samples (CTL) were procured from 20 cycling women free of endometriosis and adenomyosis, age- and menstrual phase-matched with the AM group. Additionally, primary myometrial smooth muscle cells (SMCs) derived from 15 each AM and CTL subjects, age- and menstrual phase-matched, were cultured for experiments gene and protein expression quantification and in vitro experimentation. In addition, 64 female Balb/C mice randomly assigned in equal sizes to AM and CTL groups, with mice in AM received an AM induction procedure. Every four weeks post-induction until the 12th week, eight mice from each group were sacrificed, and their myometrial tissues were harvested. Uterine horn tissues were harvested and processed for histochemistry, immunohistochemistry, and Masson trichrome staining. PARTICIPANTS/MATERIALS, SETTING, AND METHODS We performed Masson trichrome staining and immunohistochemistry (IHC) analysis of PIEZO1, PIEZO2, OTR, eNOS, phosphorylated eNOS (p-eNOS) and iNOS on myometrial tissue samples from AM and CTL groups. Western blotting were performed to evaluate the protein expression levels of eNOS, p-eNOS and iNOS in myometrial SMCs, and the concentration of NO metabolite was quantitated. Real-time RT-PCR and Western blotting analyses were performed to evaluate the gene and protein expression levels of PIEZO1, PIEZO2 and OTR under different substrate stiffness. The gene and protein expression levels of eNOS (and p-eNOS for protein) and iNOS were also evaluated after treatment of myometrial SMCs with PIEZO1 agonist Yoda1 and antagonist Dooku1, with or without non-selective NOS inhibitor L-NAME and selective iNOS, inhibitor, 1400 W. The promoter methylation status at PIEZO1 was evaluated by methylation-specific PCR (MSP) and PIEZO1 expression levels after treatment with valproic acid (VPA) for 5 and 10 days were also evaluated. For mouse experiment, the extent of myometrial fibrosis was quantified via Masson trichrome staining. IHC analysis of Piezo1, Piezo2, Otr, eNos, p-eNos and iNos on harvested myometrial tissue samples from AM and CTL groups was also performed. Bodyweight, hotplate latency, and uterine contractile amplitude and irregularity were measured. MAIN RESULTS AND THE ROLE OF CHANCE Reduced PIEZO1 and eNOS staining and elevated PIEZO2 and OTR staining, concordant with the extent of fibrosis, were found in myometrium from women with adenomyosis, especially in myometrium proximal to adenomyotic lesions. No difference in iNOS staining was found between AM and CTL myometrium. Myometrial staining of OTR and PIEZO2 were positively correlated but the staining levels of PIEZO1, eNOS and p-eNOS were negatively correlated with the dysmenorrhea severity. NO production was significantly reduced in AM myometrium as compared with controls. The gene and protein expression levels of PIEZO2 and OTR showed substrate stiffness dependent increase while those of PIEZO1 showed stiffness-dependent decrease. Suppression and stimulation of PIEZO1 downregulated and upregulated eNOS expression as well as increased and reduced NO production, respectively. Consistent with the human data, mice with induced adenomyosis exhibited reduced Piezo1 and eNos staining and elevated Piezo2 and Otr staining in myometrium, concordant with increased fibrosis. Uterine contractile amplitude and irregularity were also increased progressively, and correlated with myometrial Piezo1/Piezo2 staining and hotplate latency. PIEZO1 promoter was hypermethylated in myometrium from women with adenomyosis, but the treatment with VPA reactivated PIEZO1 expression. LARGE SCALE DATA N/A. LIMITATIONS, REASONS FOR CAUTION While we demonstrated stiffness-dependent reduction of PIEZO1 but increase in PIEZO2 and OTR expression, the underlying mechanisms for these changes remain unelucidated. Further, although we provided evidence that eNOS expression and NO production are determined by PIEZO1 expression levels, the precise mechanisms were not fully elucidated. WIDER IMPLICATIONS OF THE FINDINGS The stiffness-dependent increase in OTR and PIEZO2 expression, along with decreased PIEZO1 expression, underscores the progressive nature of adenomyosis. The link between PIEZO1 and eNOS, along with the discovery of PIEZO1 hypermethylation and its downstream target eNOS, highlights the importance of mechanotransduction in adenomyosis and the role of NO in uterine contractility. While our study focused on adenomyosis-associated dysmenorrhea, the PIEZO1–eNOS aberration might also occur in other uterine disorders such as fibroids, and may also be a contributing factor embryo implantation failure because of adenomyosis or other pathology. Finally, given that VPA reactivates PIEZO1 expression and subsequently induces eNOS, histone deacetylase inhibitors appear to be promising therapeutics, as have been shown in preclinical and pilot clinical studies before. STUDY FUNDING/COMPETING INTERESTS This research was supported in part by grant 82071623(SWG) from the National Natural Science Foundation of China.