Unbiased evaluation of cell-free amniotic fluid transcriptome of term and preterm infants to detect fetal maturity

Objective: Amniotic fluid (AF) is a proximal fluid to the fetus containing higher amounts of cell-free fetal RNA/DNA than maternal serum, thereby making it a promising source for novel biomarker discovery of fetal development and maturation. Our aim was to compare AF transcriptomic profiles at different time points in pregnancy to demonstrate unique genetic signatures that would serve as potential biomarkers indicative of fetal maturation. Methods: We isolated AF RNA from 16 women at different time points in pregnancy: 4 from 18-24 weeks, 6 from 34-36 weeks, and 6 from at 39-40 weeks. RNA-sequencing was performed on cell-free RNA. Gene expression and splicing analyses were performed in conjunction with cell-type and pathway inference.  Results: Sample-level analysis at different time points in pregnancy yielded a strong correlation with cell types found in the intrauterine environment and fetal respiratory, digestive and external barrier tissues of the fetus, using high-confidence cellular molecular markers. While some genes and splice variants were present throughout pregnancy, an abundant number of transcripts were uniquely expressed at different time points in pregnancy and associated with distinct fetal co-morbidities (respiratory distress and gavage feeding), indicating fetal immaturity. Conclusions: The AF transcriptome exhibits unique cell- and organ-selective expression patterns at different time points in pregnancy that can potentially identify fetal organ maturity and predict neonatal morbidity. Developing novel biomarkers indicative of the maturation of multiple organ systems can improve upon our current methods of fetal maturity testing which focus solely on the lung, and better inform obstetrical decisions regarding delivery timing. Overall design: RNA-Seq from cell-free was used to idenitfy mRNA transcripts indicative of overall fetal maturity.

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Kamath-Rayne BD, Du Y, Hughes M, Wagner EA, Muglia LJ, DeFranco EA, Whitsett JA, Salomonis N, Xu Y