Hyperglycosylated Human Chorionic Gonadotropin Production by Human Preimplantation Embryos In Vitro

Abstract

Background: Hyperglycosylated hCG (HhCG) is produced by the cytotrophoblasts during implantation in higher quantities than the traditional form of hCG. It has been reported that embryos make hCG prior to implantation, but it has not been previously investigated whether or not they also secrete HhCG. We hypothesized that human preimplantation embryos produce HhCG and that this may be a useful marker of embryo development. Objective: To investigate whether preimplantation embryos produce HhCG. Materials and Methods: Female subjects under age 38, undergoing autologous oocyte IVF, were offered participation in this study. All oocytes were cultured separately in P1 media (Irvine Scientific, CA) and transfered to fresh media daily. On day 3, embryos were assessed for cell number and grade. Discarded culture media from embryos was collected daily starting 48 hours after aspiration until embryo transfer. HhCG was measured in culture media from transfered embryos by an electrochemiluminescence immunoassay (Quest Diagnostics Nichols Institute, CA). The assay had a sensitivity of 2 pg/mL and a CV of <12%. Pregnancies were diagnosed with serum hCG measurements and ultrasound. Results: Five subjects, aged 34.0 ± 1.3 yrs (mean ± SEM), were included. From each subject 23.4 ± 2.3 oocytes, which resulted in 14.2 ± 2.2 embryos, were obtained and 2.8 ± 0.4 embryos were subsequently transfered. 80% (4/5) of the subjects had a positive pregnancy test, of which 2 resulted in ongoing pregnancies. The implantation rate was 35.7%. The HhCG level on day 2 was 4.69 ± 0.93 pg/mL compared with 4.70 ± 0.70 pg/mL on day 3 (P=.86). HhCG levels in conception cycles were 5.02 ± 1.00 pg/mL on day 2 and 5.00 ± 0.70 pg/mL on day 3, whereas in the nonconception cycle they were 3.04 ± 3.04 pg/mL on day 2(P=.45) and 2.90 ± 2.90 pg/mL on day 3 (P=.31). Embryo morphology did not correlate with HhCG levels in culture media on day 2 or 3. Conclusions: 1) Human preimplantation embryos produce HhCG in culture media in small but measurable amounts. 2) This is the first report of HhCG production by embryos. 3) HhCG levels on day 2 or day 3 do not appear to correlate with embryo morphology or pregnancy potential.