Tight Junction Assembly Ensures Maintenance of Pregnancy during Embryogenesis in a Mouse Model

Abstract

Recent studies showed that tight junctions (TJs) integrity and assembly are required for blastocyst development in mouse and pig models. However, the biological functions of TJs associated with embryo implantation and maintenance of pregnancy were not investigated yet. To examine whether disrupted TJs affect further embryo development, we employed RNAi approach and inhibitor treatment. The embryos were injected with Cxadr (Coxsackievirus and adenovirus receptor) siRNA for knock down (KD) and treated with Adam10 (A Disintegrin and Metalloproteinase specific inhibitor 10; GI254023X; SI). We compared blastocyst development and paracellular sealing assay using FITC dextran uptake between control and KD or SI embryos. Finally, we transferred control and Cxadr KD or Adam 10 SI treated blastocyst to uteri of recipients. Cxadr KD and Adam 10 SI showed lower blastocyst development and more permeable to FITC-dextran. Moreover, we observed that half of KD and inhibited embryos failed to maintain pregnancies after the second trimester. Our findings suggested that TJs integrity is required for the maintenance of pregnancy and can be used as a selective marker for the successful application of assisted reproduction technologies.

Maternal parity affects Day 8 embryo gene expression in old mares

“…This gene encodes for a transmembrane glycoprotein that is essential for tight junction formation. Tight junctions formation and integrity are essential for blastocyst development in mouse and pigs [75]. The reduction of the expression of ADAM19 in the TE of embryos from old nulliparous mares, could therefore support the hypothesis that embryo integrity is altered, leading to alteration of ion and nutrient exchanges in both TE and ICM.…”

Overview of junctional complexes during mammalian early embryonic development

“…8-cell stage mouse embryos treated with CXADR blocking antibody that has undergone Ca +2 switch demonstrate impaired blastocyst formation with significantly smaller blastocoels and significant downregulation in H19 and Cdx2, indicators of trophoblast lineage commitment ( 150 , 156 , 157 ). In parallel, CXADR siRNA injection into 1-cell mouse zygotes causes reduced blastocyst formation and gene expression involved with AJ (CDH1 ), TJ ( OCLN, TJP1, CLDN4 ) and lineage specification ( Nanog, Cdx2, Oct4, TEAD4, YAP1 )( 151 , 158 ). In addition, when CXADR knockdown blastocysts are transferred into surrogates, the implantation rate is significantly lower than the control.…”

“…In addition, when CXADR knockdown blastocysts are transferred into surrogates, the implantation rate is significantly lower than the control. Half of the knockdown embryos fail to maintain pregnancy after the second trimester, evaluated by gradual weight gain after embryo transfer ( 158 ). Therefore, CXDR is involved in cellular adhesion between blastomeres, TJ assembly, TE lineage diversification and pregnancy maintenance during embryogenesis.…”