The Chromosomal Constitution Of Human Abnormal Zygotes And Embryos

Objective:The aim of the study was to analyze the chromosomal constitution of human abnormal zygotes and embryos by traditional chromosomal preparation technique in single cell.Methods:352 abnormal zygotes and embryos, including 348 tripronuclear (3PN) zygotes and embryos from IVF, 4 monopronuclear (1PN) oocytes from ICSI, were collected 24～72h after insemination during April to December 2008. They were cultured with colcemid at the final concentration of 0.10ug/ml for 14～20h. Embryos were disaggregated into single blastomeres, following the removal of zona pellucida by Tyrode's solution. Each cell was treated with 0.9% sodium citrate solution, then fixed by gradual fixation, digested with pancreatic enzyme and stained with Giemsa step by step. The chromosomes were analyzed routinely.Results:(1)The chromosomal preparaton of the zygotes and embryos from IVF-3PN: The mitotic index and the success rate of preparation were the highest in 3PN-zygotes (67.6% and 52.1%, respectively), compared with 2-cell embryos (38.2% and 31.2%, respectively) and > 2-cell embryos (16.2% and 8.2%, respectively).(2)The chromosomal constitution of the zygotes and embryos from IVF-3PN: The rate of tripoid in the zygotes and 2-cell embryos were 75.7% and 70.8%, compared with 9.3%in > 2-cell embryos. In the latter, most chromosomes were near-diploid and near-haploid and the karyotype was dramatic chaotic.(3)The chromosomal constitution of the embryos from ICSI-1PN: 29 blastomeres were obtained from 4 1PN-ICSI embryos. 6 of them can be analyzed for chromosome counting and the haploid status was observed in all of them.Conclusions:(1)Traditional chromosomal preparation would involve a full karyotype analysis in metaphase chromosomes. The difficulties in karyotyping studies of human zygotes and embryos restrain the application of this technique. The technique should be upgraded furthermore.(2)The zygotes and 2-cell embryos derived from IVF-3PN are mostly triploid, whereas a significantly higher proportion of cells from > 2-cell embryos do not develop into triploid and the chromosomal constitution is dramatic chaotic.(3)ICSI-1PN embryos are mostly haploid.(4)The embyos from IVF-3PN and ICSI-PN can not be transferred in clinic.