Cleavage stage mitochondrial DNA is correlated with preimplantation human embryo development and ploidy status
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BACKGROUND: Men with oligoasthenoteratozoospermia (OAT) frequently undergo intracytoplasmic sperm injection (ICSI) as a treatment for their infertility. However, there is an increased risk of transmitting chromosomal abnormalities to the offspring given that natural selection is bypassed by the use of this technique and patients have an increased rate of sperm aneuploidy which, in addition, may negatively affect ICSI outcome. For this reason, the rate of sperm aneuploidy in unselected patients undergoing ICSI and its impact on ICSI performance have been evaluated. METHODS: Aneuploidy and diploidy were evaluated in spermatozoa separated by swim-up for oocyte injection, using DNA probes for chromosomes 8, 12, 18, X and Y. RESULTS: ICSI patients had sperm aneuploidy and diploidy rates significantly higher than those of 13 normozoospermic men who served as controls. Although the total aneuploidy rate varied considerably between the 18 patients, 15 of them (83%) had values above the upper range of the control group. Eighteen ICSI cycles were performed with an overall fertilization rate of 95% and a pregnancy rate of 39%. The aneuploidy rate of the 11 patients whose wives did not achieve pregnancy was slightly higher than that of pregnant couples, but the difference did not reach statistical significance. However, 10 patients in this group (91%) had a sperm aneuploidy rate well above the upper limit of the controls as compared with two patients in the `pregnant' group (29%). CONCLUSIONS: This study has shown that unselected patients undergoing ICSI had an elevated sperm aneuploidy rate. Lack of pregnancy was associated with a tendency towards an increased aneuploidy rate; however, pregnancy occurred even in the presence of an elevated sperm aneuploidy rate.
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Abstract To examine the pluripotency of cryopreserved blastomeres, we transplanted them into blastula. Donor blastomeres were prepared from blastula of goldfish ( Carassius auratus ) and cryopreserved in liquid nitrogen for two months. Fifty‐five percent and 44% of blastomeres survived after thawing. Cryopreserved blastomeres were transplanted to the blastula of triploid crucian carp ( C. a. longsdorfii ), which reproduces gynogenetically in nature. At four days after the operation, resultant chimeric embryos transplanted with cryopreserved blastomeres showed a survival rate (41.6%) lower than that of embryos transplanted with unfrozen blastomeres (57.1%). Transplanted blastomeres were histologically identified in various organs derived from all three germ layers. A primordial germ cell differentiated from a cryopreserved blastomere was detected in one of the 32 chimeric fish examined. These results suggest blastomeres that survive after cryopreservation retain their pluripotency and are able to differentiate into both somatic and germ cell lines. J. Exp. Zool. 301A:131–138, 2004. © 2004 Wiley‐Liss, Inc.
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By using simple electrofusion method, two blastomeres from blastula stage of goldfish were fused for the first time. Under optimum condition, the fusion rate is more than 95%. The developmental potential for the nucleus of the fused cell was tested through transplanting it into an enucleated unfertilized egg. Nuclei of 111 fused cells were transplanted, of which 44 developed into blastula stage, seven out of the 44 further developed into gastrula stage and one of the seven finally developed into a larva. DNA contents of the nuclei from eleven blastulae derived from the nuclear transplants were measured after Hoechest 33258 staining with fluorescence microphotometry. In nine cases the DNA contents showed far greater changes than those frome normal fertilized blastulae. The results suggest that exogenous chromosome may be transferred into embryos or adults with the method of electrofusion. This technique opens up a new venue for studying the heredity of somatic cells and gene transfer in fish.
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Preimplantation Genetic Diagnosis
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Embryo quality
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Analysis for the dorsalization potency of the animal blastomeres of the 16 cell stage Xenopus embryo
The derso-ventral axis of Xenopus embryo is established after fertilization. Blastula stage blastomeres acquire different identities as they have inherited different maternal materials which distribute radial symmetrically along the animal vegetal aixs in the full-grown oocyte, and are rearranged by the cortical rotation triggered by fertilization. The vegetal blastomeres demonstrate the different dorsalization potencies in the previous transplantation experiments. The data of blastomere explanting and RT-PCR analyzing indicate that the dorsal ventral bias also exists among the animal blastomeres even during the early blastula stage.
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Polarity in embryogenesis
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To analyze the influence of intracytoplasmic sperm injection (ICSI) on early embryo development used for reinsemination of unfertilized 1-day-old oocytes.Prospective observational study.A total of 126 embryos resulted from reinsemination by ICSI were analyzed with regard for the time course of cleavage and the quality of embryos at 48 hours after injection. Results were compared with those obtained in 698 embryos obtained after routine ICSI program.It has been shown that embryos derived from reinsemination developed slower in comparison with those obtained after regular ICSI program. At 48 hours after microinjection 50% of embryos achieved 4 blastomeres stage and 37% remained on 2 cells stage. 71% of regular ICSI embryos at this same time showed 4 blastomere or more, only 16% remained on 2 blastomeres stage. The quality of embryos was similar in two compared groups, however those obtained following reinsemination at 4 blastomere stage were significantly poorer quality.Embryos derived from reinsemination of 1-day old oocytes unfertilized after conventional IVF developed slower and the quality of embryos at 4 blastomere stage was poorer comparing to regular ICSI embryos.
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