Abnormal miR-122-5p expression in decidual NK cells and its impact on trophoblast behavior: insights into unexplained recurrent pregnancy loss

In the early stages of pregnancy, the maternal-fetal interface is enriched with natural killer (NK) cells that release growth factors to support fetal development and promote the remodeling of uterine spiral arteries. Previous studies have shown that the aberrant frequency and activity of decidual natural killer (dNK) cells are associated with recurrent pregnancy loss (RPL). Various factors regulate the roles of dNK cells and their interactions with trophoblasts to facilitate the colonization and maturation of semiallogeneic embryos. However, knowing precise molecular mechanisms involved in this requires further investigation. Earlier studies revealed that microRNAs (miRNAs) play a significant role in regulating the functions of decidual stromal and trophoblast cells. Although there are few studies on the intervention of malfunctioning dNK cells, this strategy shows promise in regulating abnormal miRNA production in NK cells. This study confirmed miR-122-5p downregulation in dNK cells from patients experiencing unexplained RPL. miR-122-5p regulates apoptosis, inflammatory factor secretion, and cytotoxicity of NK cells. miR-122-5p may contribute to immune tolerance at the maternal-fetal interface by targeting transcription factor T-bet. This study provides a deeper understanding of the mechanisms by which miR-122-5p regulates the function of dNK cells and trophoblasts at the maternal-fetal interface to ensure successful pregnancy.