Stromal cell decidualization and embryo implantation: a vulnerable step leading to successful pregnancy

Endometrial stromal cell decidualization is a crucial step in endometrial remodeling during pregnancy.Decidualization is controlled by orchestrated ovarian hormones,followed by the activation of various downstream signaling pathways.Accumulating evidence has shown multiple functions of decidualized endometrial stromal cells during embryo implantation,including tissue remodeling,antioxidative stress,angiogenesis,and immune tolerance.The distinct secretomes of decidualized stromal cells also reveal their intensive interactions with epithelial,endothelial,and immune cells.However,aberrant decidualization leads to pregnancy failures,such as recurrent pregnancy loss and repeated implantation failure.This review aimed to provide an overview of the molecular mechanisms underlying the divergent functions of decidualized endometrial stromal cells and their potential clinical applications.Moreover,the use of single-cell RNA sequencing data further enhances our understanding of these biological processes.This review discusses decidualization-related signaling pathways that serve as potential therapeutic targets for treating implantation failure in in vitro fertilization and provides novel approaches to investigate the underlying causes of female infertility.

An update on hormonal regulation of early embryo-fallopian tube interactions: insights for improvements of assisted reproductive technology outcomes

Human fallopian tubes(FTs)play important roles in the whole reproductive process.FTs are the site for the final maturation of gametes,fertilization,transport of preimplantation embryos,and early embryonic development before entering the uterus.All these functions are critical in the establishment of a successful pregnancy.When the embryo is in transit through the FT,the FT microenvironment changes through endocrine,paracrine,autocrine,and juxtacrine mechanisms which involve various hormones and bioactive substances mainly from the neighboring cells.Therefore,the interactions between the embryo and the FT may be the earliest embryo-maternal communications that are essential for the establishment of pregnancy.This review critically discusses the evidence of various hormonal and bioactive mediated control of the microenvironment in the FTs during the earliest embryo-maternal communications.Moreover,we highlight existing gaps in the knowledge and the importance of exploring more of the physiology of FTs which will hold the key to producing high-quality embryos for patients seekingin vitro fertilization(IVF)treatments.

Role of microRNAs in embryo–endometrial interactions:biological functions and clinical applications

The human endometrium and embryo both produce microRNAs(miRNAs),which are involved in various physiological activities.Accumulating evident suggested that endometrial miRNAs are regulated by steroid hormones that modulate endometrial functions,whereas embryo-derived miRNAs play vital roles in maternal–embryo communication.The aberrant expression of endometriumor embryo-derived miRNAs can cause early pregnancy and gestational disorders,including repeated implantation failure,recurrent miscarriage,and pathological conditions such as endometriosis.miRNAs are,therefore,ideal candidates for conducting clinicopathological tests.Potential diagnostic and prognostic tests using miRNAs are under development;however,the therapeutic applications of miRNAs in regulating gestational disorders require further investigation.