Overview and recent developments in cell-based noninvasive prenatal testing

Abstract

Investigators have long been interested in the natural phenomenon of fetal and placental cell trafficking into the maternal circulation. The scarcity of these circulating cells makes their detection and isolation technically challenging. However, as a DNA source of fetal origin not mixed with maternal DNA, they have the potential of considerable benefit over circulating cell-free DNA-based noninvasive prenatal genetic testing (NIPT). Endocervical trophoblasts, which are less rare but more challenging to recover are also being investigated as an approach for cell-based NIPT. We review published studies from around the world describing both forms of cell-based NIPT and highlight the different approaches' advantages and drawbacks. We also offer guidance for developing a sound cell-based NIPT protocol.

Figure 1.. Cell-based NIPT workflow.

(Created with BioRender.com)

Figure 2.. Timeline depicting milestones in the field of noninvasive prenatal testing.

Figure 3.. Immunostaining images of circulating trophoblasts.

The staining antibody cocktail includes anti-cytokeratin (CK; green) and anti-CD45 (yellow) antibodies, and DAPI nuclear stain. Panel A depicts a single trophoblast with a maternal cell, panel B a trophoblast doublet and panel C a cluster of three trophoblasts. Panels D, E, and F illustrate the respective DAPI staining and nuclear morphology. Panels G through K demonstrate the diversity in CK staining patterns that can be seen.

Figure 4.. Whole genome profiles from circulating trophoblasts.

[A] High-quality whole genome profile of a single trophoblast obtained from a pregnancy with a male fetus. The profile was obtained by comparison to a female reference, hence the relative loss of one X chromosome and the relative gain of Y. [B] Whole genome profile of a male trophoblast presumed in S-phase. Random gains and losses can be seen throughout the genome. [C] Whole genome profile demonstrating genomic degradation of an apoptotic trophoblast. [D] Whole genome plots specifically depicting the copy number gains (blue) and losses (red) detected in all three cells above. All profiles were created in NxClinical (BioDiscovery).