Quantifying soluble HLA-G in supernatants of cultured embryos as a marker of implantation potential in an assisted reproduction program

Abstract

HLA-G plays a tolerogenic function at the maternal-fetal interface. Detection of the soluble isoforms of HLA-G (sHLA-G) in culture medium derived from embryos grown in vitro, although technically complex, has gained interest in assisted reproduction programs because of an apparent relationship with embryo competence. Here, an amplified ELISA was designed to measure sHLA-G at the concentrations expected in embryo supernatants using a limiting-dilution assay of the choriocarcinoma JEG-3 cell line as a surrogate model. With this ELISA approach, 111 single embryo culture supernatants, collected 44-48 hours after intracytoplasmic sperm injection, were retrospectively analysed and levels correlated with pregnancy results. The presence of sHLA-G was demonstrated in 22 (19.8%) of the embryo cultures. There was no relationship between sHLA-G levels and grading of embryo morphology. The reproductive outcome of the morphologically normal embryos that were transferred to the women uterus (2-3 per patient) was as follows: in the group of women in which all transferred embryos were sHLA-G negative, the pregnancy and implantation rates were 29% (4 pregnancies/14 women) and 14% (5 gestational sacs/35 embryos transferred), respectively. In contrast, in the group in which the embryo transfers included at least one sHLA-G positive the pregnancy and implantation rates increased to 60% (3/5) and 29% c(4/14) respectively. In conclusion, sHLA-G levels in preimplantation embryo supernatants can be quantified and results suggest positive association with pregnancy likelihood. sHLA-G detection seems to be useful to complement morphology in selecting good quality embryos for increasing implantation rates and reducing multiple gestations.