Epithelial-Mesenchymal Transitions Leading to Conceptus Adhesion in Ruminants: Early Pregnancy Events in Cattle

Trophoblast-endometrium interactions play a critical role in the processes of conceptus elongation, attachment, and adhesion, followed by placental development during early pregnancy in ruminants. The attachment between uterine epithelium and trophoblast cells, which is epithelial in nature, requires epithelial to mesenchymal transition (EMT), where the fetal trophoblasts come into contact with maternal epithelial cells without fully invading the maternal tissues. Understanding the early developmental period driving EMT processes in utero in ruminants is fundamental to improving fertility through the prevention of early pregnancy failure and enhancing overall reproductive efficiency in livestock. This review highlights the key events necessary for the early conceptus to progress properly towards firm adhesion with the endometrium, focusing on trophoblast-endometrium interactions. This field holds the potential to elucidate molecular and cellular mechanisms associated with trophoblast and endometrium attachment and adhesion, leading to reduced early embryonic losses and enhanced economic sustainability by developing effective reproductive management strategies.