Analysis of uterine CD49a^(+) NK cell subsets in menstrual blood reflects endometrial status and association with recurrent spontaneous abortion

Maternal uterine immune cells,especially natural killer(NK)cells,are important for successful pregnancy,and an abnormal number or function of uterine NK cells is closely correlated with an impaired endometrial environment and miscarriage.However,there are currently no noninvasive testing methods using reliable indicators that accurately predict uterine changes leading to miscarriage.Here,we confirmed that before implantation,menstrual blood(MB)from healthy donors had 70%CD49a^(+)tissue-resident NK(trNK)cells,the majority of which were CD49a^(+)Eomes+NK cells.Importantly,MB from patients with recurrent spontaneous abortion(RSA)had many fewer CD49a^(+)trNK cells than MB from controls.Analysis of uNK cell populations in MB may better predict an abnormal endometrial environment associated with miscarriage than peripheral blood(PB)analysis.Therefore,we suggest using MB-and CD49a-related markers as a promising noninvasive way to evaluate endometrial status.