Non-invasive preimplantation genetic testing for putative mosaic blastocysts: a pilot study

• Published in: Human reproduction (Oxford) 2021-07, Vol.36 (7), p.2020-2034
• Main Authors: Li, Xinyuan, Hao, Yan, Chen, Dawei, Ji, Dongmei, Zhu, Wanbo, Zhu, Xiaoqian, Wei, Zhaolian, Cao, Yunxia, Zhang, Zhiguo, Zhou, Ping
• Format: Article
• Language: English
• ISSN: 0268-1161; 1460-2350
• DOI: 10.1093/humrep/deab080

What is the potential of applying non-invasive preimplantation genetic testing (niPGT) for chromosome abnormalities in blastocysts reported with a mosaic trophectoderm (TE) biopsy? niPGT of cell-free DNA in blastocyst culture medium exhibited a good diagnostic performance in putative mosaic blastocysts. Advances in niPGT have demonstrated the potential reliability of cell-free DNA as a resource for genetic assessment, but information on mosaic embryos is scarce because the mosaicism may interfere with niPGT. In addition, the high incidence of mosaicism reported in the context of PGT and the viability of mosaic blastocysts raise questions about whether mosaicism really exists. The study was performed between May 2020 and July 2020. First, clinical data collected by a single-center over a 6-year period on PGT for chromosome aneuploidies (PGT-A) or chromosomal structural rearrangements (PGT-SR) were analyzed. After confirming the reliability of niPGT, 41 blastocysts classified as mosaics by trophectoderm (TE) biopsy were re-cultured. The chromosomal copy number of the blastocyst embryo (BE, the gold standard), TE re-biopsy, and corresponding cell-free DNA in the culture medium was assessed. Data on patients enrolled for PGT at a single center from 2014 to 2019 were collected and the cycles with available putative mosaic blastocysts were evaluated. To verify the diagnostic validity of niPGT, eight aneuploid blastocysts were thawed and re-cultured for 14-18 h. The concordance of the niPGT diagnosis results and the whole blastocyst testing results was analyzed. Forty-one blastocysts reported as mosaics from 22 patients were included and re-cultured for 14-18 h. The genetic material of the BE, TE re-biopsy, and corresponding cell-free DNA in the culture medium was amplified using multiple annealing and looping-based amplification cycles. The karyotype data from niPGT and TE re-biopsy were compared with that from the whole blastocyst, and the efficiency of niPGT was assessed. Data on 3738 blastocysts from 785 PGT-A or PGT-SR cycles of 677 patients were collected. According to the TE biopsy report, of the 3662 (98%) successfully amplified samples, 24 (0.6%) yielded no results, 849 (23.2%) were euploid, 2245 (61.3%) were aneuploid, and 544 (14.9%) were mosaic. Sixty patients without euploid blastocysts opted for a single mosaic blastocyst transfer, and 30 (50%) of them obtained a clinical pregnancy. With the BE chromosome copy number as the gold standard, niPGT and