miRNAs in umbilical cord tissue in neonates with different birth weights: a pilot study

Background: Birth weight has been defined as an indicator of perinatal health. miRNAs are small non-coding RNA molecules between 18 and 25 nucleotides that regulate gene expression. Specific miRNAs have been implicated in metabolic pathways that influence fetal growth, so their dysregulation may contribute to birth weight alterations. Our objective was to recover amplifiable miRNAs from umbilical cord tissue and to compare their expression among three groups of patients. Methods: The study was conducted in a sample 23 patients: 8 small for gestational age (SGA), 10 large for gestational age (LGA) and 5 appropriate for gestational age (AGA) subjects. Umbilical cord tissue samples were obtained immediately after childbirth, stored and then processed. miRNAs expression profile was analyzed in these samples through high-throughput sequencing. The results were assessed through bioinformatic analysis. Results: We identified significant differences in levels of 6 miRNAs. Compared with AGA and LGA, miR-324-3p was downregulated in SGA, miR-337-3p was upregulated in LGA in comparison to both SGA and AGA, miR-760 was downregulated in LGA compared to SGA and AGA, and miR-4707-3p, miR-548a-3p and miR-6733-5p were upregulated in both SGA and LGA in comparison to AGA. Most of these molecules could be associated with the transforming growth factor-beta signaling pathway. Conclusions: This exploratory study suggests that the expression of miRNAs in umbilical cord tissue is associated with birth weight. Our findings highlight the downregulation of miRNA-324-3p in SGA newborns, leading us to conclude that its decrease could serve as a marker for low birth weight.