A Novel Non-Metabolic Function of Lactate in Remodeling Uterine Receptivity by Inducing Endometrial Histone Lactylation, Revealed by a Proteomic Atlas of Maternal-Fetal Crosstalk in Sheep

Abstract Well-orchestrated maternal-fetal crosstalk involves secreted ligands, interacting receptors, and coupled pathways between the conceptus and endometrium. However, previous researches mainly focused on either the conceptus or endometrium in isolation. The lack of integrated analysis, especially on protein levels, has made it challenging to advance our understanding of the crosstalk. Herein, focusing on ligand–receptor complexes and coupled pathways at maternal-fetal interface in sheep, a well-established embryo implantation model, we provide the first comprehensive proteomic atlas of ligand-receptor-pathway cascades that are essential for implantation. Based on these candidate interactions, we further revealed the physical interaction of albumin-claudin 4 and their role in facilitating embryo attachment to endometrium. More interestingly, we demonstrated a novel non-metabolic function of enhanced conceptus glycolysis in remodeling uterine receptivity, by inducing endometrial histone lactylation, a newly identified histone modification. Our results from in vitro and in vivo models supported the essential role of lactate, as a key pregnancy recognition signal, in regulating redox homeostasis and apoptotic balance to ensure successful implantation. Our study identified many putative molecular and cellular mechanisms that fine-tuned conceptus-endometrium crosstalk during implantation, thus providing important clues for developing potential clinical intervention strategies to improve pregnancy outcomes following both natural conception and assisted reproduction.