Metabolomics and its application for non-invasive embryo assessment in IVF

Abstract

Morphology and cleavage rate remain the mainstay of embryo assessment. However, a number of additional technologies for this application are under investigation. These include the measurement of glucose, lactate, pyruvate or amino acid levels in the embryo culture media, assessment of oxygen consumption by the embryo, genomic and proteomic profiling, and most recently, analytical examination of the embryonic metabolome. As the number of assisted reproduction cycles increases worldwide, improvements in the ability to quickly and non-invasively identify the best embryos for transfer remain a critical goal for reproductive medicine. Recent studies suggest that metabolomic profiling of embryo culture media using optical and non-optical spectroscopies may provide a useful adjunct to the current embryo assessment strategies and provide insight into the phenotype of embryos with increasing reproductive potential.

Figure 1:

NMR spectroscopy examples of pure component and biological fluid metabolomic analyses. (A) Known chemical shift regions for proton NMR spectroscopy (0–12 ppm). (B) Fourier transform proton NMR spectrum (0–5 ppm) of 6 mM lactic acid in water obtained using a 500 MHz Varian spectrometer. (C) Fourier transform proton NMR spectrum (0–5 ppm) of 18 mL spent IVF culture media in 600 mL 10% D2O/90% H₂O obtained using a 500 MHz Varian spectrometer. Ileu, isoleucine; Leu, leucine; Lact, lactate; Ala, alanine; Acet, acetate; Meth, methionine; Glu, glutamate; Pyr, pyruvate; Gluc, glucose.

Figure 2:

NIR spectroscopy examples of pure component and biological fluid metabolomic analyses. (A) Known combination and overtone NIR vibrational absorption bands of organic molecules visible between 700 and 2500 nm. (B) NIR spectrum (900–1700 nm) of 200 mM lactic acid in phosphate buffered saline (PBS). Distinct absorption bands are visible for water (1390–1590 nm) and lactic acid (1650–1700 nm). (C) NIR spectrum (900–1700 nm) of spent IVF culture media (G1; VitroLife AB, Goteborg, Sweden) supplemented with 5% human serum albumin (HSA; Irvine Scientific, Santa Ana, CA, USA). Broad combination and overtone vibrational bands are characteristic of these spectra.

Figure 3:

Raman spectroscopy examples of pure component and biological fluid metabolomic analyses. (A) Known fundamental IR vibrational absorption bands of organic molecules visible between 400 and 4000 cm⁻¹. (B) Raman spectrum (0–4000 cm⁻¹) of lactic acid. (C) Raman spectrum (0–3400 cm⁻¹) of spent IVF culture media (G1, VitroLife AB) supplemented with 5% human serum albumin (HSA; Irvine Scientific).

Figure 4:

Asymmetrical and symmetrical vibrational modes of water.

Figure 5:

Viability scores calculated using (A) NIR and (B) Raman spectra of culture media are shown for embryos that implanted and lead to delivery (empty), and those that did not implant (shaded). The implantation index values were significantly different between the two groups assessed by both NIR and Raman spectroscopy (P < 0.001). Modified from Seli et al. (2007).