The loss of dNK1/2 and EVT1 cells at the maternal–fetal interface is associated with recurrent miscarriage

Recurrent miscarriage is a chronic and heterogeneous pregnancy disorder lacking effective treatment. Alterations at the maternal-fetal interface are commonly observed in recurrent miscarriage, with the loss of certain cell subpopulations believed to be a key cause. Through single-cell sequencing of recurrent miscarriage patients and healthy donors, we aim to identify aberrancy of cellular features in recurrent miscarriage tissues, providing new insights into the research. Natural killer cells, the most abundant immune cells in the decidua, are traditionally classified into dNK1, dNK2, and dNK3. In this study, we identified a new subset, dNK1/2, absent in recurrent miscarriage tissues. This subset was named because it expresses biomarkers of both dNK1 and dNK2. With further analysis, we discovered that dNK1/2 cells play roles in immunoregulation and cytokine secretion. On the villous side of the interface, a notable decrease of extravillous trophoblast cells was identified in recurrent miscarriage tissues. We clustered extravillous trophoblasts into EVT1 (absent in recurrent miscarriage) and EVT2 (retained in recurrent miscarriage). Pseudotime analysis revealed distinct differentiation paths, identifying CCNB1, HMGB1, and NPM1 as EVT1 biomarkers. Additionally, we found that EVT1 is involved in the regulation of cell death, while EVT2 exhibited more angiogenic activity. Cell communication analysis revealed that interaction between EVT1 and dNK1/2 mediates chemotaxis and endothelial cell regulation, crucial for spiral artery remodeling. The loss of this interaction may impair decidualization, which is associated with recurrent miscarriage. In summary, we propose that the loss of dNK1/2 and EVT1 cells is a significant pathological feature of recurrent miscarriage. SUMMARY SENTENCE: The communication between EVT1 and dNK1/2 mediated the chemotaxis of EVT1 and facilitated regulation of endothelial cell death, initiating spiral artery remodeling. The loss of this specific cellular interaction may result in impaired decidualization, leading to recurrent miscarriage.