Expression of placenta-specific 8 in human oocytes, embryos, and models of in vitro implantation.

OBJECTIVE: To determine whether placenta-specific 8 (PLAC8) is expressed in human oocytes and embryos, and whether PLAC8 interferes with the implantation process.

DESIGN: Experimental.

SETTING: Academic medical assisted reproduction center.

PATIENT(S): Couples undergoing in vitro fertilization and embryo transfer (IVF-ET) cycles.

INTERVENTION(S): Quantitative polymerase chain reaction (qPCR), immunofluorescence on oocytes, embryos, control LoVo cells, and embryo-endometrial stromal cell coculture models, and Western blot on control LoVo cells.

MAIN OUTCOME MEASURE(S): Detection of PLAC8 mRNA in three oocytes, nine cleavaged embryos, three morulae, and three blastocysts, and detection of PLAC8 protein expression pattern in 12 oocytes, 16 cleavaged embryos, 7 morulae, and 18 blastocysts and in 25 hatched blastocyst-endometrial stromal cell coculture models.

RESULT(S): Single oocyte/embryo qPCR revealed PLAC8 mRNA expression was only identified in morulae and blastocysts and not in earlier stages. The immunofluorescence assay confirmed the presence of PLAC8 protein in the cytoplasm of all human oocytes and embryos preceding implantation. PLAC8 protein was transported into the nucleolus after blastocyst implantation and invasion into endometrial stromal cells.

CONCLUSION(S): Our data have demonstrated for the first time that human oocytes and preimplantation embryos express PLAC8 and that the intracellular distribution of PLAC8 protein is dynamic and regulated in an implantation-dependent manner. These findings indicate that PLAC8 plays a potential role in embryo development and implantation.