Group B Streptococcal Infection of the Choriodecidua Induces Dysfunction of the Cytokeratin Network in Amniotic Epithelium: A Pathway to Membrane Weakening

Abstract

Early events leading to intrauterine infection remain poorly defined, but may hold the key to preventing preterm delivery. To determine molecular pathways within fetal membranes (chorioamnion) associated with early choriodecidual infection that may progress to preterm premature rupture of membranes (PPROM), we examined the effects of a Group B Streptococcus (GBS) choriodecidual infection on chorioamnion in a nonhuman primate model. Ten chronically catheterized pregnant monkeys (Macaca nemestrina) at 118–125 days gestation (term = 172 days) received choriodecidual inoculation of either GBS (n = 5) or saline (n = 5). Cesarean section was performed in the first week after GBS or saline inoculation. RNA extracted from chorioamnion (inoculation site) was profiled by microarray. Single gene, Gene Set, and Ingenuity Pathway Analysis results were validated using qRT-PCR (chorioamnion), Luminex (amniotic fluid, AF), immunohistochemistry, and transmission electron microscopy (TEM). Despite uterine quiescence in most cases, significant elevations of AF cytokines (TNF-α, IL-8, IL-1β, IL-6) were detected in GBS versus controls (p<0.05). Choriodecidual infection resolved by the time of cesarean section in 3 of 5 cases and GBS was undetectable by culture and PCR in the AF. A total of 331 genes were differentially expressed (>2-fold change, p<0.05). Remarkably, GBS exposure was associated with significantly downregulated expression of multiple cytokeratin (CK) and other cytoskeletal genes critical for maintenance of tissue tensile strength. Immunofluorescence revealed highly significant changes in the CK network within amniocytes with dense CK aggregates and retraction from the cell periphery (all p = 0.006). In human pregnancies affected by PPROM, there was further evidence of CK network retraction with significantly shorter amniocyte foot processes (p = 0.002). These results suggest early choriodecidual infection results in decreased cellular membrane integrity and tensile strength via dysfunction of CK networks. Downregulation of CK expression and perturbations in the amniotic epithelial cell intermediate filament network occur after GBS choriodecidual infection, which may contribute to PPROM.

Choriodecidual Group B Streptococcal Infection Induces miR-155-5p in the Fetal Lung in Macaca nemestrina

“…All surgery was performed while the animals were under general anesthesia, and all efforts were made to minimize suffering. A description of the chronically catheterized pregnant nonhuman primate model of choriodecidual GBS infection, including details on animal care, analgesia, surgery, fetal euthanasia and necropsy, and fetal lung pathology and scoring, has been previously reported (12,15). Briefly, 10 chronically catheterized pregnant nonhuman primates (Macaca nemestrina) at 118 to 125 days of gestation (term ϭ 172 days) received one of two experimental treatments: (i) choriodecidual and intra-amniotic fluid saline infusions (the saline control group, n ϭ 5) or (ii) GBS choriodecidual inoculations (the GBS group; n ϭ 5).…”

The common vaginal commensal bacterium Ureaplasma parvum is associated with chorioamnionitis in extreme preterm labor

“…However like U. parvum it was more common with earlier gestational delivery, suggesting GBS might have a non-inflammatory role in preterm labour. One possible explanation for this might be linked to the recent observation in gravid primates that in-utero infection with GBS can result in the down regulation of multiple cytokeratins and other cytoskeletal genes critical for maintenance of cellular membrane integrity and tensile strength, potentially leading to preterm labour [43]. These changes took place in the absence of inflammation.…”

Prevention of preterm birth: Harnessing science to address the global epidemic

“…www.ScienceTranslationalMedicine.org 12 November 2014 Vol 6 Issue 262 262sr5membranes (74). Finally, PPROM has been associated with genetic disorders of collagen structure, such as Ehlers-Danlos syndrome (75), and with a variety of single-nucleotide polymorphisms (76).…”