A single-cell transcriptomic atlas of severe intrauterine adhesion

Intrauterine adhesion (IUA) is a common endometrial disease caused by injury, leading to reproductive health issues. Current treatments have limited effectiveness, side effects, and high recurrence rates, especially, in severe cases. However, the underlying molecular and cellular mechanisms are largely unknown. Here we performed a comprehensive analysis by profiling integrated single-cell transcriptomes of over 72,000 individual endometrial cells, encompassing samples from both patients with IUA and those with normal endometrium. We identified changes in cell type-specific molecular signatures, including the inflammatory activation in immune cells, extensive damage in epithelial subpopulations, and the deposition of collagen secreted by fibroblasts subpopulations. Our results demonstrated activation of the TREM2⁺ macrophages, which displayed properties of inflammatory regulation. Annexin A1⁺ NK subpopulations exhibited the highest susceptibility among NK subtypes, displaying decreased cellular density and the most pronounced differential gene expression. Furthermore, we identified the matrix metallopeptidase 7 (MMP7⁺) and C-C motif chemokine ligand 5 (CCL5⁺) unciliated epithelial subtype originated from pituitary tumor-transforming gene 1 (PTTG1⁺) unciliated epithelium as the most vulnerable subpopulations to epithelial injury. Collectively, our study offers integrated resources of the cellular microenvironment of IUA, serving as a comprehensive cellular map of the disease in affected individuals. The insights gained from this study are expected to provide valuable resources for future diagnostic and therapeutic approaches.