*Article* **Identifying Stabilin-1 and Stabilin-2 Double Knockouts in Reproduction and Placentation: A Descriptive Study**

**Soon-Young Kim 1,2, Eun-Hye Lee <sup>1</sup> , Eun Na Kim <sup>3</sup> , Woo-Chan Son <sup>3</sup> , Yeo Hyang Kim 4,5 , Seung-Yoon Park <sup>6</sup> , In-San Kim 7,8 and Jung-Eun Kim 1,2,\***


Received: 20 August 2020; Accepted: 29 September 2020; Published: 30 September 2020

**Abstract:** The placenta undergoes reconstruction at different times during fetal development to supply oxygen and nutrients required throughout pregnancy. To accommodate the rapid growth of the fetus, small spiral arteries undergo remodeling in the placenta. This remodeling includes apoptosis of endothelial cells that line spiral arteries, which are replaced by trophoblasts of fetal origin. Removal of dead cells is critical during this process. Stabilin-1 (Stab1) and stabilin-2 (Stab2) are important receptors expressed on scavenger cells that absorb and degrade apoptotic cells, and Stab1 is expressed in specific cells of the placenta. However, the role of Stab1 and Stab2 in placental development and maintenance remain unclear. In this study, we assessed Stab1 and Stab2 expression in the placenta and examined the reproductive capacity and placental development using a double-knockout mouse strain lacking both Stab1 and Stab2 (Stab1/2 dKO mice). Most pregnant Stab1/2 dKO female mice did not produce offspring and exhibited placental defects, including decidual hemorrhage and necrosis. Findings of this study offer the first description of the phenotypic characteristics of placentas and embryos of Stab1/2 dKO females during pregnancy, suggesting that Stab1 and Stab2 are involved in placental development and maintenance.

**Keywords:** Stabilin-1; Stabilin-2; double knockout; placenta; decidua; hemorrhage
