Stereological study of the placental structure in abortion-prone mice model (CBA/J×DBA/2J)

Recurrent spontaneous abortion (RSA) is an important reproductive health issue defined as the loss of two or more consecutive pregnancies before the 20th week of gestation, affecting 2-5% of couples. This study aimed to evaluate the volume, number of cells, and length of the vessels in the placenta in normal and abortion-prone (AP) pregnant mice on gestational day (gd) 13.5. Fetal and placental tissues of female CBA/J mated DBA/2J (AP group) and BALB/c (normal pregnant group) were collected and prepared for stereological assessments on gd13.5. The volumes of the placenta and its main layers decidua basalis (Db), junctional zone (Jz), and labyrinth zone (Lz) were investigated. The number of spongiotrophoblast cells, glycogen cells, giant cells, trophoblast cells, lymphocytes, and neutrophils were estimated as well. The AP group showed a reduction in the volume of the placenta (48.7%) and its components. Moreover, the number of spongiotrophoblast cells (66.7%), glycogen cells (76.2%), giant cells (73.3%), and trophoblast cells (81.4%) was decreased in AP compared to normal pregnant (NP) mice. Also, in AP group recognized a 10-fold increase in the number of lymphocytes and a four-fold increase in the number of neutrophils in comparison to the NP group (p < 0.05). Activation of different immune cell types might induce systemic inflammation at the feto-maternal interface, resulting in impaired placenta formation and abortion.