Interaction of decidual macrophages and other maternal-fetal interface cells in recurrent pregnancy loss

Recurrent Pregnancy Loss (1) is a common pregnancy complication that can have a negative impact on both the physical and mental health of pregnant women. Despite various associations, the precise etiology of RPL remains unclear, necessitating further research. Immune cells are recognized to play a pivotal role in successful pregnancy. This article focuses on the role of macrophages, the second most abundant leukocyte population in the decidua. Decidual macrophages are instrumental in promoting embryo implantation and maintaining immune homeostasis. Macrophages are traditionally categorized into activated M1 and alternatively activated M2 states, each serving distinct immunological roles, but in fact this classification is no longer applicable. In this review, we discussed the classification of decidual macrophages and their impact on embryo implantation and development, including their regulation of trophoblasts and decidual stromal cells, and explore their potential association with RPL. Macrophages play a role in regulating both trophoblasts invasion and apoptosis processes. We also discuss how trophoblasts and decidual stromal cells influence macrophages. Additionally, we explored the interplay between macrophages and immune cells, such as T cells, NKs and DCs, to uncover the potential link between macrophage-related immune regulation and RPL. While substantial knowledge exists regarding the role of macrophages in pregnancy regulation, many aspects remain obscure. Thus, this review aims to discuss the interaction between decidual macrophages and other cells at the maternal-fetal interface, exploring their connection to RPL.