L26/O-328 Spatial transcriptomic insights between eutopic endometrium, ectopic endometriosis and adenomyosis lesions

Abstract Study question What spatially resolved transcriptional differences distinguish matched eutopic endometrium, ectopic endometriosis and adenomyosis lesions with comparison to control endometrium? Summary answer Compartment and layer-specific transcriptional heterogeneity exists between ectopic endometriosis lesions and eutopic and control endometrium, with immune pathways differing between endometriosis and adenomyosis. What is known already Endometriosis is a chronic gynaecological condition characterised by the growth of endometrium outside of the uterine cavity. It causes chronic pelvic pain, infertility and can significantly impact quality of life. Recent studies have suggested that there is a disruption of immune cell recruitment and recognition that allows endometriotic lesions to flourish in a pro-inflammatory, immunosuppressive state. Single cell and spatial studies have implicated altered B cell, T-cell, natural killer cell and fibroblast signalling pathways. Study design, size, duration This is a translational study using FFPE (formalin fixed, paraffin embedded) endometrial and ectopic endometrial tissue, and control endometrial tissue. The cohort consisted of 25 patients including balanced numbers of secretory and proliferative phase samples and a smaller group of inactive endometrium due to exogenous hormonal treatment. Samples were collected through Liverpool Women’s Research Tissue Bank Participants/materials, setting, methods A tissue microarray was generated form the above patient samples. Spatial transcriptomics was performed using the Nanostring GeoMx platform. Different cellular compartments were delineated using CD45 (immune), cytokeratin (epithelial) and CD10 (stromal) markers. Differential gene expression (DEG) was examined across luminal, functionalis and basalis layers, comparing control, eutopic, ectopic and adenomyotic tissues. Main results and the role of chance The greatest number of transcriptional differences were observed between ectopic endometriosis lesions and luminal/ functionalis eutopic endometrium across all compartments. Direct comparison between eutopic and control endometrium showed relatively few DEGs suggesting there are limited transcriptional differences between eutopic and control endometrium relative to ectopic lesions. When comparing adenomyosis lesions to endometriotic lesions the DEG burden was highest within the CD45 compartment, suggesting differential immune regulation between these conditions. Ectopic lesions showed an upregulation of genes associated with oxidative stress and mitochondrial function (e.g. HIGD1C, ND5) and downregulation of pathways regulating natural killer and T-cell activity, consistent with an immunosuppressive lesion environment. Limitations, reasons for caution Sample size limits subgroup analyses particularly for adenomyosis and hormonal subgroups. These results also require further validation in a larger independent cohort. Wider implications of the findings These findings identify spatially restricted molecular pathways that could serve as biomarkers for endometriosis and support the discovery of therapeutic targets to improve targeted immunomodulatory therapies for endometriosis and adenomyosis. Trial registration number No