Gasdermin D: in vivo evidence of pyroptosis in spontaneous labor at term

Abstract

Objective: Pyroptosis is an inflammatory form of programmed cell death that is mediated by the activation of the inflammasome and depends on the pore-forming function of gasdermin D. Therefore, the detection of gasdermin D represents in vivo evidence of pyroptosis. We recently showed that there is intra-amniotic inflammasome activation in spontaneous labor at term; however, evidence of pyroptosis is lacking. The objectives of this study were to investigate (1) whether gasdermin D is detectable in the amniotic fluid of women who delivered at term; (2) whether amniotic fluid gasdermin D concentrations are associated with the process of spontaneous labor at term; and (3) whether gasdermin D is expressed in the chorioamniotic membranes from these patients.

Methods: This retrospective cross-sectional study included amniotic fluid samples from 41 women who underwent spontaneous labor at term (n = 17) or delivered at term without labor (n = 24). As a readout of pyroptosis, gasdermin D was determined in amniotic fluid samples using a specific and sensitive ELISA kit. The 90th percentile of amniotic fluid gasdermin D concentrations was calculated among women without spontaneous labor at term (reference group). The association between high amniotic fluid gasdermin D concentrations (≥90th percentile in the reference group) and spontaneous labor at term was tested using the Fisher’s exact test. A p value <.05 was considered significant. Multiplex immunofluorescence staining and phenoptics (multispectral imaging) were performed to determine gasdermin D expression in the chorioamniotic membranes and to colocalize this protein with the inflammasome-related molecules caspase-1 and interleukin-1β.

Results: (1) Gasdermin D is present in the amniotic fluid of women who delivered at term; (2) the 90th percentile of amniotic fluid gasdermin D concentrations in women who delivered at term without spontaneous labor was 3.4 ng/mL; (3) the proportion of women with amniotic fluid gasdermin D concentrations above the threshold was higher in those who underwent term labor than in those who delivered at term without labor; (4) amniotic fluid concentrations of gasdermin D > 3.4 ng/mL were significantly associated with the presence of spontaneous labor in women who delivered at term (odds ratio 6.0, p-value .048); and (5) the protein expression of gasdermin D is increased in the chorioamniotic membranes of women who underwent spontaneous labor at term and is colocalized with caspase-1 and IL-1β.

Conclusions: Gasdermin D is increased in the amniotic fluid and chorioamniotic membranes of women who underwent spontaneous labor at term compared to those without labor. These data provide evidence implicating pyroptosis in the mechanisms that lead to the sterile inflammatory process of term parturition.

Keywords:

• Caspase-1
• chorioamniotic membranes
• inflammasome
• interleukin-1beta
• parturition
• pregnancy
• sterile inflammation

Acknowledgements

We gratefully acknowledge the PRB Translational Research Laboratory for their contributions to the execution of this study. We thank the physicians and nurses from the Center for Advanced Obstetrical Care and Research and the Intrapartum Unit for their help in collecting human samples. The authors also thank the staff members of the PRB Clinical Laboratory and the PRB Histology/Pathology Unit for the processing and examination of the pathological sections.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported, in part, by the Perinatology Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, U.S. Department of Health and Human Services (NICHD/NIH/DHHS); and, in part, with Federal funds from NICHD/NIH/DHHS under Contract No. HHSN275201300006C. This research was also supported by the Wayne State University Perinatal Initiative in Maternal, Perinatal and Child Health.