Boros-Rausch, A.; Ballan, N.; Celik, I.; Dorogin, A.; Gillespie, Z.; Mitchell, J.; Grainger, D.; Fox, D.; Shynlova, O.; Lye, S.

Preterm birth (PTB) is a leading cause of perinatal and infant mortality worldwide. PTB can be induced by systemic maternal or intra-uterine infection or by sterile intra-amniotic inflammation driven by alarmins such as interleukin-1 (IL-1). We reported earlier that Broad-Spectrum Chemokine Inhibitor (BSCI) prevented PTB in murine and non-human primate models of infection-mediated preterm labor. Here, we investigated whether BSCI can prevent PTB in pregnant C57BL/6 mice following ultrasound-guided intra-amniotic injection of IL-1 (400 ng per sac) on gestational day (GD)16.5. Half the mice received BSCI (10 mg/kg, intravenous daily) beginning GD15.5 and through to term. The impact of IL-1 alone or IL-1 plus BSCI was assessed on (i) injection-to-delivery interval, fetal survival, placental and neonatal weight; (ii) cytokine and chemokine levels in maternal plasma and amniotic fluid (by Luminex assay) and inflammatory gene expression in maternal and fetal tissues (by Real-Time RT-PCR); (iii) global multi-omic profiling of myometrial tissues, including gene expression (RNA sequencing), chromatin accessibility and regulatory landscape (ATAC-seq), and protein abundance profiling by tandem mass spectrometry (TMT-MS proteomics); (iv) uterine leukocyte infiltration (by immunofluorescence with automated quantification). Pre-treatment with BSCI i) prevented IL-1-induced PTB; (ii) significantly attenuated cytokine and chemokine signals in maternal plasma, myometrium, decidua, and placenta, and amniotic fluid; (iii) suppressed myometrial contraction-associated genes, including Nfkb1, Ptgs2, Akr1c18, and Gja1; (iv) prevented broad IL-1-induced changes in myometrial gene expression, chromatin accessibility, and proteomic extracellular matrix (ECM) structural remodeling; (v) reduced uterine F4/80+ macrophage counts and changed M1-M2 balance. BSCI-treated dams that delivered at term had live pups with normal placental and fetal weight. Taken together, BSCI reduced the incidence of IL-1-mediated PTB and maintained uterine quiescence by suppressing uterine inflammation and global changes in labor gene expression and chromatin accessibility. BSCI represents a promising therapeutic approach for PTB prevention in high-risk pregnant women.