Blastocentesis A source of DNA for preimplantation genetic testing Results from a pilot study

Capsule:
DNA retrieved by blastocentesis provided a chromosome condition that was highly correspondent with that found in trophectoderm cells. Results from polar bodies and blastomeres were also predictive of the blastocyst’s ploidy.

Authors:
Luca Gianaroli, M.D., M. Cristina Magli, M.Sc., A. Pomante, Ph.D., Anna M. Crivello, B.Sc., G. Cafueri, B.Sc., M. Valerio, B.Sc., Anna P. Ferraretti, M.D.

Volume 102, Issue 6, Pages 1692-1699

Abstract:

Objective:
To investigate the presence of DNA in blastocyst fluids (BFs) and to estimate whether the chromosomal status predicted by its analysis corresponds with the ploidy condition in trophectoderm (TE) cells, the whole embryo, and that predicted by polar bodies (PBs) or blastomeres.

Design:
Prospective study.

Setting:
In vitro fertilization unit.

Patient(s):
Seventeen couples undergoing preimplantation genetic screening with the use of array comparative genomic hybridization on PBs (n = 12) or blastomeres (n = 5).

Intervention(s):
BFs and TE cells were retrieved from 51 blastocysts for separate chromosomal analysis.

Main Outcome Measure(s):
Presence of DNA in BFs and assessment of the corresponding chromosome condition; correlation with the results in TE cells and those predicted by the analysis done at earlier stages.

Result(s):
DNA was detected in 39 BFs (76.5%). In 38 of 39 cases (97.4%) the ploidy condition of BFs was confirmed in TE cells, and the rate of concordance per single chromosome was 96.6% (904/936). In relation to the whole embryo, the ploidy condition corresponded in all cases with a per-chromosome concordance of 98.1%. The testing of PBs and blastomeres had 93.3% and 100% prediction of BF ploidy condition with a concordance per chromosome of 93.5% and 94%, respectively.

Conclusion(s):
Blastocentesis could represent an alternative source of material for chromosomal testing, because the BF is highly predictive of the embryo ploidy condition and chromosome content. Our data confirm the relevance of the oocyte and of the early-cleavage embryo in determining the ploidy condition of the resulting blastocyst.

  • Shvetha Zarek

    Thank you for an interesting proof of concept paper! This was a prospective study of 17 couples undergoing a combination of either polar body biopsy or blastomere biopsy at the 6-8 cell stage and trophoectoderm biopsy at the blastocyst stage with aspiration of blastocyst fluid, termed as blastocentesis. A total of 51 blastocysts were evaluated for blastocyst fluid (BF) presence. Whole genome amplification and CGH was utilized to provide DNA results. Of the 51 blastocysts, 12 failed to provide BF results. Of the remaining 39 blastocysts, 37 (94.9%) demonstrated total ploidy concordance with full chromosome concordance in 29 blastocysts.

    This is an interesting concept study that provides an alternative to TE biopsy. However, the technology had a number of limitations that will require further validation before consideration as an alternative source for PGS testing. There is no indication that blastocentesis would be a safe alternative since the tested blastocysts were not reported to have been utilized in an ART cycle to achieve pregnancy. Thank you to the esteemed authors for an excellent study.

    • Luca Gianaroli

      Thank you for your comment and interest in our work.

      You raised an important point stating that the two limitations of
      blastocentesis reside 1) in the high proportion of blastocyst fluids failing
      to provide a diagnosis, and 2) in the fact that no biopsied blastocysts were
      proven to be able to produce a pregnancy.

      Regarding the first point, we are currently trying to identify possible
      factors predicting the finding of DNA in the blastocyst fluid. The time of
      blastocentesis could be relevant at this respect. At this stage of our
      research, after analyzing 94 blastocyst fluids, we have found DNA in 75 of
      them corresponding to 80% (the rate was 76.5% in our paper on 51
      blastocysts).

      For the second point, I have to say that it is common pratice in several
      laboratories, including ours, to collapse blastocysts before vitrification.
      In our hands, the rewarming of artificially collapsed blastocysts has a 100%
      survival rate with pregnancy and implantation rates of 43 and 37.5%
      respectively.

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