OBJECTIVE: To evaluate the safety and accuracy of karyotyping the blastomere chromosomes at metaphase in the natural cell cycle for preimplantation diagnosis. DESIGN: A pilot study. SETTING: A private infertility clinic and a university laboratory. PATIENT(S): Eleven patients undergoing IVF and preimplantation diagnosis. INTERVENTION(S): Intact human embryos at the 4- to 6-cell stage and human-mouse heterokaryons were cultured and checked hourly for disappearance of the nuclear envelope. After it disappeared, the metaphase chromosomes were analyzed by fluorescence in situ hybridization. MAIN OUTCOME MEASURE(S): Percentage of analyzable metaphase plates and safety and accuracy of the method. RESULT(S): The success rate of electrofusion to form human-mouse heterokaryons was 87.1% (27/31), and analyzable chromosomes were obtained from 77.4% (24/31) of the heterokaryons. On the other hand, disappearance of the nuclear envelope occurred in 89.5% (17/19) of the human embryos and it began earlier than that in the heterokaryons. Analyzable chromosomes were obtained and their translocation sites were identified in all blastomeres biopsied from the 17 embryos. After the biopsy, 67.0% of the embryos could develop to the blastocyst stage. CONCLUSION(S): The natural cell cycle method reported herein requires frequent observation, but it is safe, with no artificial effects on the chromosomes and without loss of or damage to blastomeres, which occurred with the electrofusion method. Using the natural cell cycle method, we could perform preimplantation diagnosis with nearly 100% accuracy.
OBJECTIVE: To evaluate the safety and accuracy of karyotyping the blastomere chromosomes at metaphase in the natural cell cycle for preimplantation diagnosis. DESIGN: A pilot study. SETTING: A private infertility clinic and a university laboratory. PATIENT(S): Eleven patients undergoing IVF and preimplantation diagnosis. INTERVENTION(S): Intact human embryos at the 4- to 6-cell stage and human-mouse heterokaryons were cultured and checked hourly for disappearance of the nuclear envelope. After it disappeared, the metaphase chromosomes were analyzed by fluorescence in situ hybridization. MAIN OUTCOME MEASURE(S): Percentage of analyzable metaphase plates and safety and accuracy of the method. RESULT(S): The success rate of electrofusion to form human-mouse heterokaryons was 87.1% (27/31), and analyzable chromosomes were obtained from 77.4% (24/31) of the heterokaryons. On the other hand, disappearance of the nuclear envelope occurred in 89.5% (17/19) of the human embryos and it began earlier than that in the heterokaryons. Analyzable chromosomes were obtained and their translocation sites were identified in all blastomeres biopsied from the 17 embryos. After the biopsy, 67.0% of the embryos could develop to the blastocyst stage. CONCLUSION(S): The natural cell cycle method reported herein requires frequent observation, but it is safe, with no artificial effects on the chromosomes and without loss of or damage to blastomeres, which occurred with the electrofusion method. Using the natural cell cycle method, we could perform preimplantation diagnosis with nearly 100% accuracy.