Tetraspanin CD9 regulates invasion during mouse embryo implantation

Abstract

The expression of tetraspanin CD9 was found on blastocysts in mice and endometrium epithelial cells in human and bovine. However, it remains unknown how CD9 is involved in the precise dialogue between embryo and uterus during early pregnancy. This study was designed to investigate the functional roles of CD9 in the embryo implantation with monoclonal antibody against CD9 protein (anti-CD9 mAb) and antisense oligonucleotide against CD9 gene (AS-CD9). Our results showed that intrauterine injection of anti-CD9 mAb on day 4 of pregnancy significantly increased the number of embryos implanted (7·24±0·39 versus 4·04±0·38). In vitro, anti-CD9 mAb or AS-CD9 significantly enhanced embryo-outgrowth ability on the monolayer of uterus epithelial cells in a dose-dependent manner. However, the attachment of blastocysts to epithelial cells was unaffected. Furthermore, we found that anti-CD9 mAb or AS-CD9 stimulated matrix metalloproteinase 2 (MMP-2) production of blastocysts on Fibronectin. LY294002, a specific inhibitor of phosphoinositide 3-kinase, was able to counteract the effect of anti-CD9 mAb and AS-CD9 on outgrowth ability and production of MMP-2. Our results indicated that CD9 played a role of inhibiting embryo implantation. CD9 was able to impair embryo invasion and the production of MMP-2 through the phosphoinositide 3-kinase signaling pathway.

Embryo–epithelium interactions during implantation at a glance

“…It may be that there is a complex interplay between integrins and other cell surface factors. Indeed, a number of components of the uterine cell surface have functional roles in implantation and interact with αv integrins, including CD98 (officially known as SLC3A2) (Domínguez et al, 2010), the tetraspanin CD9 (Domínguez et al, 2010;Liu et al, 2006;Wynne et al, 2006), the dipeptidyl peptidase CD26 (officially known as DPP4) (Shimomura et al, 2006), the epidermal growth factor (EGF)-domaincontaining glycoprotein MFG-E8 (Schmitz et al, 2014), the IGF receptor (Fujita et al, 2013;Kang et al, 2015), galectin 3 (Lei et al, 2009;Yang et al, 2012) and galectin 15 (Lewis et al, 2007).…”

Blastocyst elongation, trophoblastic differentiation, and embryonic pattern formation

“…The expression of CSH1 has been confirmed in the embryo before its attachment to endometrium, however, the spatial (subcellular) localization of CSH1 protein within the TGC has not been shown (Kessler et al 1991. Furthermore, CD9, a cell-surface protein implicated in cell adhesion, differentiation, and migration, is expressed in the BNC and may participate in the fusion of trophoblast cells and endometrial epithelia (Xiang & MacLaren 2002, Liu et al 2006. Therefore, the appearance of TGCs during this critical transitional stage and the TGCs' ability to produce factors, CSH1 and CD9, which enable conceptus:maternal interaction highlight the importance of this differentiated trophoblast cell type.…”

Tetraspanin CD9 in Bovine Oocytes and Its Role in Fertilization

“…This fusion competence could be restored upon injection of mRNA from either human or mouse CD9 into CD9 -/-mouse oocytes [6]. In addition, CD9 is expressed in pig oocytes during early growth and meiotic maturation and that it participates in sperm-oocyte interactions during fertilization [5].Apart from the expression of CD9 on the plasma membrane of oocytes in the mouse [2-4, 6] and pig [5] , it is also localized to the oocyte microvillar membrane [7] , blastocysts in mouse [3,8], and endometrium epithelial cells in the mouse [9], human [10] and bovine [11] . Accordingly, CD9 is required for normal microvillar shape and distribution in the mouse [7] and plays a role in inhibiting embryo implantation [8].…”

“…Apart from the expression of CD9 on the plasma membrane of oocytes in the mouse [2-4, 6] and pig [5] , it is also localized to the oocyte microvillar membrane [7] , blastocysts in mouse [3,8], and endometrium epithelial cells in the mouse [9], human [10] and bovine [11] . Accordingly, CD9 is required for normal microvillar shape and distribution in the mouse [7] and plays a role in inhibiting embryo implantation [8].…”

“…Accordingly, CD9 is required for normal microvillar shape and distribution in the mouse [7] and plays a role in inhibiting embryo implantation [8]. CD9 expression in the uterus is upregulated in an ovarian steroid hormone-dependent manner, implicating multiple roles of CD9 in regulation of embryo implantation during the peri-implantation period [9].…”