Low-Dose Aspirin and Uterine Natural Killer Cells in Mice at Day Seven of Pregnancy

Inhibiting the effect of aspirin on prostaglandin results in corpus luteum maintenance in pregnant mice. Uterine natural killer (uNK) cells activate between 5 - 7 days of pregnancy. uNK cell differentiation is indirectly regulated by ovarian hormones. Immune cells have important roles in the endometrium at early pregnancy stages. Although low-dose aspirin is effective on ovarian hormones, the effect of low-dose aspirin on the uNK cell population at early pregnancy stages is unknown. The aim of this study was to assess the effect of low-dose aspirin on uNK cells at day seven of pregnancy. Adult female mice were coupled and divided into two groups (control and experimental). Thereafter, mice in the experimental group received 7.5 mg/kg aspirin twice a day for one week. Blood samples were collected for the measurement of the level of ovarian hormones at day seven of pregnancy and finally the animals were sacrificed by cervical dislocation and uterine horns were removed for histological study. Periodic acid-schiff (PAS) staining was performed for uNK cell counting. Data analysis was conducted by SPSS software. The ovarian hormones level showed a significant difference between the experimental and control groups (P < 0.05). Furthermore, the uNK cell population showed a significant difference between the two groups (P < 0.05). Increased ovarian hormones due to low-dose aspirin administration resulted in decline in the uNK cells number, which may be effective in successful pregnancy.