Fig. 1.

The overview of the present study. Only ovulatory women with regular menstrual cycles were included. Endometrial biopsies, 10 in the adenomyosis group and 10 the in control group, were conducted between 7 and 9 days post urinary LH peak corresponding to the expected WOI. Isolated RNA samples were used for RNA-seq using the Illumina NovaSeq 6000 platform and for accurate endometrial receptivity classification using the beREADY® molecular test. When analysing transcriptomics data of all 20 LH-timed biopsies, 909 DEGs (p < 0.05, nonsignificant after corrected p value) were associated with the adenomyosis group. Downstream functional enrichment analysis of these genes identified no strong candidate mechanisms associated with endometrial molecular biology. According to endometrial receptivity testing, 2 out of 20 samples were classified as early-receptive, 13 as receptive and 5 as late-receptive during the menstrual cycle. To prevent early- and late-secretory phases of the menstrual cycle on the transcriptomics analysis associated with endometrial receptivity, samples dated to the early- and late receptive phases were omitted from the RNA-seq dataset. The remaining transcriptomics data of 8 adenomyosis cases and 5 control samples dated to the receptive phase were reanalysed. The 382 identified DEGs (p <0.05, nonsignificant after corrected p value) in the adenomyosis group were further enriched in more robust candidate pathways, including “Expression of IFN-induced genes”, “Response to interferon-alpha” and “ISG15-protein conjugation”. The 382 identified DEGs were further integrated with 42, 173 and 151 genes from the literature associated with endometrial receptivity in adenomyosis, endometriosis and healthy uterus, respectively, to propose a molecular background of endometrial receptivity under adenomyosis. Abbreviations: DEGs = differentially expressed genes; LH = luteinizing hormone; RIN = RNA integrity number; WOI = window of implantation. The images of the NovaSeq 6000 Sequencing System and Gynetics suction curette were obtained from official pages Illumina.com and gyneatic.com, respectively