Associations of Serum Inflammatory Biomarkers During Pregnancy With Placental Pathology and Placental Gene Expression at Delivery

Problem

We sought to investigate whether maternal inflammatory cytokines during pregnancy are associated with histologic inflammatory or vascular lesions in the placenta and/or correlated with gene expression patterns in the placenta.

Method of Study

We leveraged data from a large randomized controlled trial (RCT) at a single site. Maternal serum was collected in the second and third trimesters, and a composite inflammatory score was created using five measured biomarkers (CRP, IL-6, IL-1ra, IL-10, and TNF-α). Placentas were collected at delivery for histological analysis and four major patterns of placental injury were characterized. Fresh small chorionic villous biopsies were collected for placental genome-wide mRNA profiling. Transcripts showing >2-fold differential expression over the 4-SD range of circulating inflammatory biomarkers were reported, adjusting for potential confounders.

Results

The primary analysis included 601 participants. A one standard deviation increase in the third-trimester inflammatory composite was associated with increased odds of chronic inflammation in the placenta (OR: 1.23, 95% CI 1.01, 1.51;). This was driven primarily by elevations in IL-10 (OR: 1.37; 99% CI: 1.06, 1.77). Higher maternal IL-10 in circulation was associated with bioinformatic indications of reduced pro-inflammatory gene regulation pathways in the placenta (AP1 decreased 25%, p = 0.003; NF-kB decreased 53%, p = 0.003) and indications of increased STAT family signaling pathways which mediate signaling through the IL-10 receptor (increased 73%, p = 0.002).

Conclusions

Our results indicate that elevated maternal circulating IL-10 during pregnancy is associated with chronic inflammatory lesions in the placenta at delivery. Additionally, higher levels of circulating IL-10 are associated with upregulated STAT signaling pathways in placental tissues.