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- Title
Efficacy of 24 chromosome FISH analysis in preimplantation embryos.
- Authors
Fernández, S.; Colomar, A.; Toro, E.; Chamosa, S.; López-Teijón, M.; Velilla, E.
- Abstract
Aim: Recent studies have reported that analysis of a limited number of chromosomes in PGD may result in suboptimal implantation rates. The number of chromosomes tested and the choice of which chromosomes to be tested are critical in optimizing IVF outcome results. Standard FISH techniques only allow few chromosome analysis. These techniques entail an aggressive denaturalization process that progressively damages the DNA only allowing for 3 rounds of analysis. There is a pressing need to develop new techniques for the analysis of all embryo chromosomes. The objectives of this study were: (i) to develop a FISH technique for the analysis of all embryo chromosomes (FISH-24) in PGD; and (ii) to evaluate the efficacy of the newly developed FISH-24 technique. Method: Embryos from IVF-PGD cycles indicated for advanced maternal age were biopsied on day 3 of development and standard FISH analysis for 9 chromosomes (X, Y, 13, 15, 16, 17, 18, 21, 22) (FISH-9) were performed. Following PGD, 26 non-transferable embryos were maintained in culture until day 5, fixed and reanalyzed using the improved technique for 24 chromosomes (FISH-24) (Cellay, US). The results obtained by FISH-9 analysis on day 3 and FISH-24 analysis on day 5 were analysed. Results: A total of 26 embryos were reanalyzed for 24 chromosomes. Fifty percent (13/26) of the embryos showed embryo mosaicism. Of these, 76.9% (10/13) presented aneuploid events that could be detected by FISH-9 analysis, 15.4% (2/13) presented an aneuploid event combined with an aneuploid event also present in FISH-9 analysis and one embryo (7.6%) presented an aneuploid event that was only detected by FISH-24 analysis. This, could change PGD results from a 'transferable' to a 'nontransferable' embryo. Conclusion: To our knowledge, this is the first report of PGD using this newly developed FISH technique for 24 chromosomes. Our results show that: (i) there is a proportion of embryos with chromosomal abnormalities that are not detected by standard FISH-9 analysis; (ii) the efficiency of the standard FISH technique can be significantly improved (iii) the improved FISH-24 technique could be performed in day 5 transfer and easily applied to IVF-PGD cycles without extra cost for patients.
- Subjects
CHROMOSOMES; PREIMPLANTATION genetic diagnosis; HUMAN embryo research; MOSAICISM
- Publication
Reproductive BioMedicine Online (Reproductive Healthcare Limited), 2010, Vol 20, pS26
- ISSN
1472-6483
- Publication type
Article