人类低评分早期胚胎与低评分囊胚的性染色体嵌合性分析

Analysis of sex chromosome mosaicisms in early cleavage-stage human embryos and blastoeysts with poor embryo quality scores

目的应用X、Y双色荧光原位杂交（fluorescenceinsituhybridization，FISH）分析不同原核（pronucleus，PN）数量来源的低评分早期胚胎和低评分囊胚的性染色体嵌合情况并探讨其发生机理。方法对低评分、不适于胚胎移植的新鲜或冷冻-解冻的早期胚胎和囊胚进行双色FISH分析。结果2PN早期胚胎细胞中两信号率为66．67％，显著高于1PN和3PN胚胎；1PN早期胚胎细胞中单信号率为90．41％，明显高于2PN和3PN胚胎；3PN胚胎细胞中三信号率为28．00％，显著高于1PN和2PN胚胎，两信号率为46．Oo％，明显高于1PN胚胎。冷冻-解冻的早期胚胎有多信号嵌合的胚胎的比例为23．53％，高于新鲜胚胎，但差异无统计学意义。24个囊胚的嵌合率为100％，其中两信号占主导的囊胚（比例≥50％）占总数的62．50％，显著高于早期胚胎。结论以2PN作为正常受精的判断标准来选择适宜移植的胚胎已不够准确，冷冻-解冻对胚胎染色体加倍可能有一定的影响。为了避免选择染色体异常的胚胎，有必要结合胚胎植入前遗传学诊断（pre—implantationgeneticdiagnosis，PGD）以及产前诊断技术进行染色体异常筛查。此外，低评分囊胚可能是胚胎干细胞又一重要来源。

Objective To analyze sex chromosome mosaicisms in early cleavage-stage human embryos and blastocysts with poor embryo quality score based on the numbers of pronucleus（PN） zygotes using X,Y dual color fluorescence in situ hybridization （FISH）, and to discuss the possible mechanisms. Methods Fresh or frozen-thawed early cleavage-stage human embryos and blastocysts with poor embryo quality score not suitable for embryo transfer were studied with dual color FISH. Results Double signal rate of 2PN among early cleavage-stage embryos was 66. 67%, which was significantly higher than 1PN and 3PN embryos. Single signal rate of 1PN early cleavage-stage embryos was 90. 41%, which was significantly higher than 2PN and 3PN ones. Three signal rate of 3PN early cleavage-stage embryos was 28.00%, which was significantly higher than 1PN and 2PN ones. Double signal rate of 3PN ones was 46.00%, which was significantly higher than IPN ones. The polyploid rate of frozen-thawed early cleavage-stage embryos was 23.53%, which was slightly higher than that of fresh embryos, but with no statistical significance. The mosaicism rate of 24 blastocysts was 100.00% and the double signal dominant （≥50%） rate was 62.50%, which was significantly higher than the rate of early cleavage-stage embryos. Conclusion Using 2PN as the criterion for embryo quality score cannot guarantee the selection of normal fertilized embryo for transplantation. Frozen-thawed embryos may harbor more polyploid cells. To avoid the selection of embryos with abnormal chromosomes, combinations of pre-implantation genetic diagnosis （PGD） and prenatal diagnosis are necessary. Meanwhile, blastocysts with poor quality scores may provide an important source for embryo stem cells.