QUESTION –Can a difference in mass spectral data from the
culture media of embryos be used to discriminate between euploid
and aneuploid genotypes without genetic testing?
ANSWER –It is possible to identify patterns of change in mass
spectral data to discriminate between embryos with euploid and
BACKGROUND –PGS of biopsied blastocyst stage embryos is
currently used to discriminate between euploid and aneuploid
genotypes. However, randomized prospective clinical trials failed
to show an increase in live birth rates after PGS selection of
embryos. This could be assigned to technical drawbacks and
chromosomal mosaicism. Thus, the clinical cost benefits of PGS is
questioned. Nevertheless, faster and more affordable means to
screen for aneuploidies that may persist to live birth are needed. It
has been shown that MALDI-ToF mass spectrometry of embryo
culture media can detect differences between the phenotypes,
offering rapid, sensitive analysis without requirement of vitrification.
DESIGN - A retrospective cohort study, including 1190 spent media
samples from embryo cultures collected from a single IVF clinic in
USA. The samples were collected between March 2014 and March
2018. There were 149 euploid and 165 aneuploid embryos as
analysed by PGS next-generation sequencing.
METHODS –Upon receiving frozen, embryo culture media was
thawed, diluted and analysed using MALDI-ToF mass spectrometry
in a laboratory in the UK. The spectra were generated using CHCA
matrix, obtained in a mass range of 200 to 2000 m/z to identify
proteomic profile. Characteristic regions to discriminate euploids
and aneuploids, enrichment analysis and intensity differences were
obtained using automated computational workflow implemented
RESULTS –Characteristic spectral patterns composed of nine peak
regions were found in MS data of embryo culture media from
aneuploid genotypes when compared to those of euploids (Figure
1). These regions had variable window sizes, ranging from 3 to 10
m/z, each representing peaks in the spectra. This pattern
pinpointed 8 peak regions with higher enrichment in aneuploidies
when compared to euploids (Figure 1). On the other hand, four
regions had statistically significant difference in intensity with p-
value < 0.001 (Figure 2). The differences between aneuploids and
euploids were visually checked in the mass spectrum for the nine
regions. In Figure 3 it is shown an example for each region.
Sholeh Keshavarz MSc1, Fady I. Sharara MD 2,3 , Ricardo J. Pais PhD1, Raminta Zmuidinaite MSc1,
Ray K. Iles PhD 1,4, Stephen A. Butler PhD1
A NON-INVASIVE, RAPID METHOD TO DISCRIMINATE EUPLOID
AND ANEUPLOID EMBRYO BY MALDI-TOF MS OF CULTURE
1. MAP Sciences, London, UK & iLab, Bedford, UK. 2. Virginia Center for Reproductive Medicine, Reston, VA, USA. 3. George
Washington University, Washington, DC, USA. 4. Dean’s office, College of Healthcare Sciences, Abu Dhabi University, Abu
CONCLUSION –PGS is invasive, expensive and a time-
consuming test that requires embryo vitrification. Embryo
culture media analysis by MALDI offers a non-invasive method
to assess euploidy of an embryo prior to transfer which could
positively affect both clinics and patients.
Figure 3 Comparison of Euploid (teal) and Aneuploid (grey)
spectral patterns in nine regions represented in each panel.
Figure 1 Peak
Euploid of the
vs Euploids for
all nine regions.