GSE108966
A comprehensive two-centre RNA-seq study reveals changes in endometrial and blood miRNome at mid-secretory phase in fertile women and in patients with recurrent implantation failure
Study question: Does a comprehensive study involving two different population cohorts and small RNA sequencing from endometrium and blood reveal new endometrial receptivity-related microRNAs (miRNAs) in healthy conditions and in women with recurrent implantation failure (RIF)? Summary answer: Several annotated miRNAs, not previously associated with endometrial receptivity, as well as one novel miRNA were found as differentially expressed between early secretory vs. mid-secretory phase samples in addition to miRNAs dysregulated in RIF patients. What is known already: The involvement of miRNAs in mid-secretory endometrial functions has been shown and aberrant expression of miRNAs in RIF has been identified in a few previous studies, but not from whole blood samples. However, as the analysis settings and platforms have been different and a small number of samples has been analysed, there is no consensus about the miRNAs involved in endometrial receptivity and dysfunction. Participants/materials, setting, methods: A total of 116 endometrial and 114 blood samples were subjected to Illumina small RNA sequencing. Identification of annotated and novel miRNAs from sequencing reads was performed by miRDeep2 algorithm. miRNAs that had significantly altered levels between the study groups in both EST and ESP datasets were considered as differentially expressed. Ingenuity Pathway Analysis was applied for identifying miRNA target genes and respective canonical pathways from the matched mRNA analysis from the same samples. Custom TaqMan Small RNA assay was used for the validation of novel miRNA (chr2_4401) levels from paired early secretory and mid-secretory endometrial samples. Main results and the role of chance: Among fertile women, 91 differentially expressed miRNAs were identified in mid-secretory vs. early secretory endometrium, while no differentially expressed miRNAs were found in the corresponding blood samples. The comparison of mid-secretory phase samples between fertile women and RIF patients revealed 21 differentially expressed miRNAs from endometrium and one from blood samples. miRNA target gene prediction analysis using our mRNA sequencing data from the matched samples detected several canonical pathways to be involved in mid-secretory endometrial functions, including JAK/STAT signalling, leptin signalling and growth hormone signalling. Moreover, JAK/STAT signalling pathway was also revealed in miRNA target analysis of mid-secretory endometrium from RIF patients when compared to fertile women. Further, our study results highlight the involvement of miR-30 and miR-200 families in endometrial receptivity, and miR-424-5p in the development of endometrial dysfunction. We identified several novel miRNAs, of which miRNA chr2_4401, being 37-fold up-regulated in mid-secretory phase, has a potential role in the mid-secretory endometrial functions. From blood samples we identified miR-30a-5p as a possible marker of infertility related to RIF. Overall design: Our current study recruited 39 fertile women and 38 infertile RIF patients from Estonia (EST) and Spain (ESP). Paired endometrial and blood samples were collected at early secretory and mid-secretory phases from fertile women and at mid-secretory phase from infertile RIF patients. This is the largest miRNA endometrial receptivity study to date with novel aspects of combining matched samples of endometrium and blood from two different population cohorts.