Intra-amniotic inflammation is strongly associated with spontaneous preterm labor and birth, the leading cause of perinatal mortality and morbidity worldwide. Previous studies have suggested a role for the NLRP3 (NLR family pyrin domain-containing protein 3) inflammasome in the mechanisms that lead to preterm labor and birth. However, a causal link between the NLRP3 inflammasome and preterm labor/birth induced by intra-amniotic inflammation has not been established. Herein, using an animal model of lipopolysaccharide-induced intra-amniotic inflammation (IAI), we demonstrated that there was priming of the NLRP3 inflammasome (1) at the transcriptional level, indicated by enhanced mRNA expression of inflammasome-related genes (Nlrp3, Casp1, Il1b); and (2) at the protein level, indicated by greater protein concentrations of NLRP3, in both the fetal membranes and decidua basalis prior to preterm birth. Additionally, we showed that there was canonical activation of the NLRP3 inflammasome in the fetal membranes, but not in the decidua basalis, prior to IAI-induced preterm birth as evidenced by increased protein levels of active caspase-1. Protein concentrations of released IL1β were also increased in both the fetal membranes and decidua basalis, as well as in the amniotic fluid, prior to IAI-induced preterm birth. Finally, using the specific NLRP3 inhibitor, MCC950, we showed that in vivo inhibition of the NLRP3 inflammasome reduced IAI-induced preterm birth and neonatal mortality. Collectively, these results provide a causal link between NLRP3 inflammasome activation and spontaneous preterm labor and birth in the context of intra-amniotic inflammation. We also showed that, by targeting the NLRP3 inflammasome, adverse pregnancy and neonatal outcomes can be significantly reduced.

Background Decidual senescence has been considered a mechanism of disease for spontaneous preterm labor in the absence of severe acute inflammation. Yet, signs of cellular senescence have also been observed in the chorioamniotic membranes from women who underwent the physiological process of labor at term. Objective We aimed to investigate whether, in the absence of acute histologic chorioamnionitis, the chorioamniotic membranes from women who underwent spontaneous preterm labor or labor at term exhibit markers of cellular senescence. Study Design Chorioamniotic membrane samples were collected from women who underwent spontaneous preterm labor or labor at term. Gestational age-matched non-labor controls were also included. Senescence-associated genes/proteins were determined using reverse transcription quantitative polymerase chain reaction analysis (n=7–9 each for array; n= 26–28 each for validation), enzyme-linked immunosorbent assays (n=7–9 each), immunoblotting (n=6–7 each) and immunohistochemistry (n=7–8 each). Senescence-associated β-galactosidase activity (n=7–11 each) and telomere length (n=15–22 each) were also evaluated. Results In the chorioamniotic membranes without acute histologic chorioamnionitis: 1) the expression profile of senescence-associated genes was different between the labor groups (term in labor and preterm in labor) and the non-labor groups (term no labor and preterm no labor); yet, there were differences between the term in labor and preterm in labor groups; 2) most of the differentially expressed genes among the groups were closely related to the tumor suppressor protein 53 (TP53) pathway; 3) the expression of TP53 was down-regulated in the term in labor and preterm in labor groups compared to their non-labor counterparts; 4) the expression of CDKN1A (gene coding for p21) was up-regulated in the term in labor and preterm in labor groups compared to their non-labor counterparts; 5) the expression of the cyclin kinase CDK2 and cyclins CCNA2, CCNB1 and CCNE1 was down-regulated in the preterm in labor group compared to the preterm no labor group; 6) the concentration of TP53 was lower in the preterm in labor group than in the preterm no labor and term in labor groups; 7) the senescence-associated β-galactosidase activity was greater in the preterm in labor group than in the preterm no labor and term in labor groups; 8) the concentration of phospho-S6 ribosomal protein was reduced in the term in labor group compared to its non-labor counterpart but no differences were observed between the preterm in labor and preterm no labor groups, and 9) no significant differences were observed in relative telomere length among the study groups (term no labor, term in labor, preterm no labor, and preterm in labor). Conclusion In the absence of acute histologic chorioamnionitis, signs of cellular senescence are present in the chorioamniotic membranes from women who underwent spontaneous preterm labor compared to those who delivered preterm in the absence of labor. However, the chorioamniotic me...

Problem: Pyroptosis, inflammatory programmed cell death, is initiated through the inflammasome and relies on the pore-forming actions of the effector molecule gasdermin D. Herein, we investigated whether gasdermin D is detectable in women with spontaneous preterm labor and sterile intra-amniotic inflammation or intra-amniotic infection. Method of study: Amniotic fluid samples (n = 124) from women with spontaneous preterm labor were subdivided into the following groups: (a) those who delivered at term (n = 32); and those who delivered preterm (b) without intra-amniotic inflammation (n = 41), (c) with sterile intra-amniotic inflammation (n = 32), or (d) with intra-amniotic infection (n = 19), based on amniotic fluid IL-6 concentrations and the microbiological status of amniotic fluid (culture and PCR/ESI-MS). Gasdermin D concentrations were measured using an ELISA kit. Multiplex immunofluorescence staining was also performed to determine the expression of gasdermin D, caspase-1, and interleukin-1β in the chorioamniotic membranes. Flow cytometry was used to detect pyroptosis (active caspase-1) in decidual cells from women with preterm labor and birth. Results: (a) Gasdermin D was detected in the amniotic fluid and chorioamniotic membranes from women who underwent spontaneous preterm labor/birth with either