microRNA expression in innate lymphoid cells from human decidua

Innate lymphoid cells are a heterogeneous subset of lymphocytes deeply implicated in the innate immune responses to different pathogens, in lymphoid organogenesis and in the maintenance of tissue homeostasis. Group 3 innate lymphoid cells (ILC3) have been detected in human decidua, where they play a role in the early inflammatory phase favoring implantation and tissue remodeling as well as in the subsequent regulatory phase preventing fetal rejection and supporting neoangiogenesis. A balance between inflammation and immune tolerance is required to maintain pregnancy, thus maternal immune system must be controlled by finely tuned mechanisms. MicroRNAs (miRNAs) are small non-coding RNAs with important regulatory roles in immune cells, but their function in decidual ILC3 (dILC3) and decidual NK (dNK) cells is still undefined. Here, we examined the miRNome by microarray in these cells during the first trimester of pregnancy and compared with miRNA profiles of peripheral blood NK (pbNK) cells from pregnant women. We show that distinct miRNA profiles could clearly distinguish dILC3 from NK cells. Correlation analyses revealed that dNK and pbNK miRNome profiles are more similar to each other as compared to dILC3. Overall, our data identified specific miRNA signatures distinguishing dILC3, dNK and pbNK cells. NCR+ dILC3 and dNK cells were isolated from decidua basalis of healthy pregnant women undergoing voluntary termination of pregnancy in the first trimester of gestation, applying a multi-parametric cytofluorimetric gating strategy. In order to perform an Affymetrix microRNA microarray analysis, three samples of sorted dILC3 were analyzed (pool #1: three patients; pool #2: five patients; pool #3: three patients). Further, five samples of sorted dNK were included in the microarray: three samples derived from the same pools used for dILC3, plus two additional non-pooled dNK samples. Finally, the microarray analysis included four samples of pbNK isolated from peripheral blood of four healthy pregnant women undergoing voluntary termination of pregnancy in the first trimester of gestation.