Telomere length in trophectoderm and inner cell mass of human blastocysts: comparative analysis and assessment of influencing factors

BACKGROUND: The study of telomere length and influencing factors in early human development has both fundamental and applied importance. AIM: A comparative assessment of telomere length in the compartments of human blastocysts, and the analysis of the telomere length association with the quality of blastocysts, genetic imbalance and the maternal age. MATERIALS AND METHODS: The study was performed on trophectoderm and inner cell mass samples of 41 human blastocysts, 26 of which were genetically imbalanced according to preimplantation genetic testing and verification of its results. The microscope slides were prepared for further telomere detection in interphase nuclei by quantitative fluorescence in situ hybridization (Q-FISH). RESULTS: Telomeres in trophectoderm were longer than in inner cell mass, with their length varied from blastocyst to blastocyst. Telomere length in either trophectoderm or inner cell mass did not differ between genetically balanced and imbalanced blastocysts. There was a tendency towards a decrease in telomere length in the blastocyst compartments with increasing maternal age, however, a statistically significant correlation was not confirmed. The telomere length in the inner cell mass, but not in the trophectoderm, was associated with blasocysts’ quality based on the Gardner grade: medium quality blastocysts had longer telomeres than high quality blastocysts. CONCLUSIONS: Long telomeres in trophectoderm may be necessary for implantation and subsequent placentation. Telomere length can be considered among modifiers of the effects of karyotype abnormalities and other negative factors: the inheritance by an embryo of long telomeres apparently gives it a developmental advantage even when genetically imbalanced or has poor morphology. Implantation seems to be an important checkpoint for negative selection of embryos with “unsuccessful” combinations of telomere length, karyotype, and morphology.