BeWo-Derived Extracellular Vesicles Downregulate IL-6Rα Expression via miRNAs on CD4+ T Lymphocytes

A balanced Th1/Th2/Th17/Treg status is necessary for a successful pregnancy. T cell polarization depends on the local cytokine environment and the responsiveness of T lymphocytes to cytokines. Trophoblast-derived extracellular vesicles (EVs) influence the function of maternal T lymphocytes, contributing to their polarization into the Treg phenotype. We examined whether BeWo-derived EVs affect T cell IL-6 responsiveness using the BeWo cell line as an experimental model and characterized the molecular cargo of BeWo -EVs that may contribute to this process.

Circulating lymphocytes from non-pregnant women were treated with BeWo-EVs or co-cultured with BeWo cells. We detected IL-6Rα expression by flow cytometry and IL6R signaling pathways by RT-PCR. The microRNA (miRNA) content of BeWo EVs was identified by sequencing. Finally, we compared IL-6Rα expression levels in circulating T lymphocytes from healthy pregnant and non-pregnant women.

BeWo-EVs reduced IL-6Rα expression on CD4+ T cells. This modifies the IL-6 pathway by downregulating the transcription factors STAT3, NFKB1, and PIAS3 while upregulating STAT1. This may be due to the presence of specific microRNAs (miRNAs), such as hsa-mir-92a-3p, hsa-mir-520f-3p, and hsa-mir-25-3p, in BeWo-EVs that target the IL-6 pathway. Treatment with BeWo-EVs also induced phenotypic and functional changes in T cells and enhanced the ratio of CD4+/CD25+ T cells that produce IL-10. Pregnancy-associated IL-6Rα downregulation has been demonstrated in clinical samples. Significantly lower levels of IL-6Rα were detected on circulating CD4+CD25+ T cells in healthy pregnant women compared to healthy non-pregnant individuals.

Our studies suggest that the microRNA content of trophoblast-derived EVs significantly influences the local polarization of maternal T lymphocytes by modifying the IL-6Rα signaling pathway.