EMBRYONIC HUMAN-LEUKOCYTE ANTIGEN-G EXPRESSION - POSSIBLE IMPLICATIONS FOR HUMAN PREIMPLANTATION DEVELOPMENT

Objective: To investigate further the association between human leukoc yte antigen G (HLA-G) expression in human embryos and other factors kn own to influence IVF pregnancy outcome. Setting: A university-based te rtiary referral center (The Toronto Hospital). Interventions: Nontrans ferred embryos at the two- to four-cell stage were obtained from patie nts undergoing IVF and were cultured in Ham's F-10 medium supplemented with 10% human sera or cocultured with ovarian cancer cells in the sa me medium. Embryos that reached blastocyst stage (n = 148) were analyz ed by reverse transcriptase-polymerase chain reaction for HLA-G and be ta 2 microglobulin (beta 2m) expression. Statistical analysis was perf ormed to identify possible factors associated with variability of expr ession. Results: Approximately 40% of studied blastocysts had detectab le expression of both HLA-G and beta 2m messenger RNA. In 46% of blast ocysts, beta 2m alone was observed. Interestingly, sibling embryos fro m patients that became pregnant were significantly more likely to expr ess HLA-G than embryos from patients that did not conceive as a result of their IVF cycles. No association was found between HLA-G expressio n and culture conditions, patient age, or infertility diagnosis. Concl usion: The population of embryos obtained through IVF is heterogeneous in expression of HLA-G and beta 2m, which may reflect overall health of the embryos. Blastocysts showing positive HLA-G expression may have increased viability and implantation potential, although the underlyi ng mechanisms remain to be elucidated.