Investigating the role of trophoblast-derived CXCR3 dysfunction in inflammatory-driven spontaneous preterm birth

Background: Preterm birth, delivery before 37 weeks’ gestation, affects approximately 15 million births annually, leading to nearly 1 million deaths. Disproportionately preterm birth affects lower-middle-income countries, with a rate of one-in-six births in Bangladesh. Preterm birth is a complex multifactorial condition which, despite its global impact, has incompletely understood pathogenesis. Adaptation of the maternal immune system is essential to maintain fetal tolerance at the maternal–fetal interface. Disruption of this is a proposed mechanism underlying spontaneous preterm labour. CXCR3, a transmembrane immune receptor implicated in transplant rejection, may contribute to this process. We hypothesised that dysregulation of placental CXCR3 contributes to preterm birth pathology. Methods: CXCR3 and its ligands CXCL10 and CXCL9 were measured in clinical samples from preterm and term pregnancies. BeWo and HTR-8/SVNeo cells were subject to inflammatory stimuli, and changes in CXCR3 and CXCL10 expression were analysed. Results: CXCR3 was detected in placental biopsies by immunostaining and was strongly expressed by extravillous trophoblasts and syncytiotrophoblasts. Preterm placenta showed significantly increased CXCR3 expression. In term placentas, CXCR3 expression was predominantly localised to extravillous trophoblasts, whereas this was less distinct in preterm placentas. CXCL10 and CXCL9 were detectable in second-trimester vaginal fluid from women who later delivered at term or preterm. In preterm samples, CXCL10 and CXCL9 concentrations did not correlate to other cytokines, unlike term samples. In vitro, trophoblast cells strongly expressed CXCR3 and CXCL10 following TLR-3, but not TLR-4, stimulation. Syncytialised cells expressed CXCR3, suggesting functional as well as pathological relevance. Conditioned media from TLR-3-stimulated trophoblasts induced CXCR3 upregulation on CD4+ and CD8+ T cells and promoted migration. Conclusions: These findings demonstrate trophoblast-driven inflammatory signalling consistent with maternal–fetal immune rejection in preterm birth. Finally, a prototype microfluidic device was developed for bedside detection of biomarkers for preterm birth in low-volume samples.