Winter 2008

A New Method for Embryo Selection: Metabolomics

By Emre Seli, MD

Using a model based on glutamate and alanine/lactate ratio quantities, Seli and co–workers demonstrated that embryos with proven reproductive potential have significantly higher viability indices compared to embryos that did not implant. Proton NMR spectroscopy identified implantation/pregnancy with a sensitivity of 88.2% and a specificity of 88.2%.

Infertility centers in the United States attain relatively high success rates following in vitro fertilization (IVF), in many cases through the simultaneous transfer of multiple embryos. In 2006, IVF programs transferred a mean number of 2.45 embryos during IVF cycles, leading to a 34.3% live birth rate, of which 32.0% were multiple–infant live births. Even in cases where embryos possessed the highest reproductive potential (oocyte donation), programs transferred a mean number of 2.3 embryos and 40.8% of the pregnancies resulted in multiple–infant live births. In total, more than 30% of Assisted Reproductive Technology (ART) pregnancies are twins or higher–order multiple gestations, and 51% of all ART neonates are the products of multiple gestations, a frequency 15– to 20–fold greater than with spontaneous conceptions. Consequently, decreasing multiple gestations while maintaining or improving overall pregnancy rates remains a significant contemporary goal in the treatment of infertility.

Raman spectral analysis of culture media segregates embryos that implanted and led to delivery (red) and those that did not implant (blue).

The sentinel issue surrounding multiple gestations following IVF is the inability to precisely estimate the reproductive potential of individual embryos. Grading systems based on embryo morphology and cleavage rates have been the mainstay of embryo assessment worldwide. Unfortunately, they are not sufficiently precise to compel most patients and clinicians to reduce the number of embryos transferred to a point where twins are uncommon and higher–order multiple gestations are rare or eliminated entirely.

The limitations of morphologic evaluation of embryos have led many investigators to pursue adjunctive technologies for assessment of the reproductive potential of a given embryo. Several metabolic parameters of developing embryos have been measured using a number of non–invasive techniques. However, these technologies are expensive, require dedicated equipment and technical staff that would be cost–prohibitive in most embryology laboratories, and frequently do not produce results quickly enough to allow the information to be used clinically in the limited window of time acceptable for embryo transfer. Moreover, none of the technologies has ever been validated using culture media evaluated in a blinded fashion and shown to correlate with the implantation potential of embryos that have been transferred. Therefore, the need remains to identify a technology that predicts embryo viability through a rapid, non–invasive, consistent, and clinically applicable platform.

Drs. Emre Seli and Denny Sakkas from our department, in collaboration with Prof. Dave Burns from McGill University and Molecular Biometrics, Inc., have recently reported results from a multi–center study using a non–invasive spectroscopic method for prediction of the implantation potential of embryos in IVF. In this study, they tested the hypothesis that the metabolism of embryos that result in pregnancy is different than that of embryos that do not, and that the difference may be detected by the rapid, non–invasive evaluation of the embryo culture media using spectroscopic analysis and bioinformatics, also called metabolomics. The team evaluated spent culture media of transferred embryos using Raman and near–infrared (NIR) spectroscopy. Spectroscopic analysis successfully predicted the implantation potential of embryos. They confirmed the results of the initial study in a second trial using samples collected in a blinded manner, and predicted outcome with a sensitivity of more than 70%.

Typical Nuclear Magnetic Resonance spectrum of embryo culture media, showing differing concentrations of key metabolites.

Most recently, the research team used proton nuclear magnetic resonance (1H NMR) and identified glutamate in the embryo culture media as a determinant of embryo viability. The research team will present the results of this study at the American Society for Reproductive Medicine (ASRM) annual meeting, where the work was selected as a prize paper candidate. The technology is expected to be available worldwide before the end of the current academic year.