A-340 Uterine natural killer cells are decreased during the proliferative phase in case of endometriosis and adenomyosis

Abstract Background In the non-pregnant endometrium, uterine natural killer cells cells (uNK) are mostly inactive but have the ability to undergo differentiation through the menstrual cycle in preparation for pregnancy. After implantation of the embryo, uNK participates in the process of placentation by facilitating trophoblast invasion and spiral artery remodelling to allow adequate exchange of nutrients and oxygen between mother and baby. The presence of uNK cells was significantly higher in women with endometriosis compared with controls in secretory phase. However, the function of uNK cells during the proliferative phase remains unclear in the current literature. In this study, we tried to find the association between the uNK and recurrent miscarriage (RM), recurrent implantation failure (RIF) , chronic endometritis (CE) and other gynecological and obstetric condition such as adenomyosis ,Endometriosis… etc. Methods The endometrial tissues of 80 women under the age of 45 without underlying medical conditions, immune diseases, malignancies, or current use of immunosuppressants were obtained for this study. All participants had signed the informed consent from the IRB approval. The levels of uNK cells were assessed through immunohistochemistry using CD56+, with results presented as the absolute number per high power field (HPF). The recurrent miscarriage (RM) was defined as having two or more previous miscarriages and recurrent implantation failure (RIF) was defined as having two or more unsuccessful pregnancy following embryo transfers in fresh or frozen cycles. Chronic endometritis (CE) was defined as with the level above 5 CD138 + cells/HPF. Endometriosis was diagnosed through histological or imaging methods. Results Among the 80 cases, 25 cases (31%) had uNK counts ranging from 0 to 10/HPF, 25 cases (31%) ranging from 11 to 20/HPF, and the remaining 30 cases (38%) had uNK counts greater than 20/HPF, respectively. The expression of CD56+ shows significantly statistical difference between patients with or without endometriosis (p-value: 0.004) and adenomyosis (p-value: 0.024).However, it does not show statistical significance between individuals with or without RM (p-value:0.698), RIF (p-value:0.690) and CE (p-value:0.744). When using >16 uNK/HPF as the criteria, the statistical results are consistent with the criteria only using the presence or absence of CD56+ cells. Conclusion We found there is relatively reduced levels of uNK of women with endometriosis and adenomyosis during proliferative phase. The same phenomenon was also confirmed in the experiments using animal models (data not shown). The presence and quantity of uNK cells may be linked to the development or progression of these conditions, making them a potential biomarker for differentiation between endometriosis or adenomyosis. Our study underscores the significantly reduced levels of uNK cells in the endometrium of women with endometriosis during proliferative phase, suggesting possible alterations in the immune environment associated with endometriosis. However, due to the single-center nature of our study and a relatively small sample size, more large-scale longitudinal studies are necessary to confirm our findings and to investigate the underlying pathophysiology between endometriosis/ adenomyosis and uNK cells.