Chemokine Receptor Type 4 Regulates Migration and Invasion of Trophectoderm Cell in the Human Blastocyst

ABSTRACT Chemokine receptor type 4 (CXCR4) has been suggested to regulate cell migration and invasion in human somatic cells. However, its role in human oocytes and embryos has not been investigated directly. Here we show that CXCR4 mRNA was initially expressed at the 4-cell stage, and its expression gradually increased until the blastocyst stage, whereas its protein was detectable only after the 8-cell stage. In addition, CXCR4 mRNA and protein were expressed in the inner cell mass (ICM) and trophectoderm (TE) cell of the blastocyst. Furthermore, we collected embryos from women whose embryos had undergone successful implantation (SI) and those whose embryos had failed implantation (FI) in their fresh cycles. TE cells from the FI group had reduced CXCR4 mRNA expression relative to those from the SI group but not in the ICM. Through ICM replacement, we constructed mouse blastocysts in which Cxcr4 was specifically knocked down in TE cells to simulate the CXCR4 expression profile of human blastocysts from th...