Buderatska N. Preimplantation genetic screening of embryos after cryopreservation of human oocytes by vitrification

The study object was the changed chromosomal status of human preimplantation embryos obtained from fertilized oocyte, affected by vitrification. The purpose of the work was to determine the quantitative chromosomal abnormalities rate of preimplantation human embryos obtained from fertilized and cryopreserved oocytes with different initial morphological characteristics and on the basis of the results obtained to develop criteria for evaluating their cryoresistance and euploidity of chromosomes. Methods used were as follows: molecular genetic; molecular cytogenetic; cultural; light, confocal, fluorescence and polarized microscopy; cryobiological and the ones of statistical processing of the results. Theoretical and practical results, scientific novelty are as follows: for the first time a new criteria for the morphological evaluation of extra- and intracytoplasmic structures of oocytes were proposed to predict their cryoresistance. For the first time, no negative influence of cryopreservation factors on the chromosomal set of embryos derived from vitrified oocytes has been demonstrated by means of next-generation sequencing and fluorescence in situ hybridization. The chromosomal aneuploidy rate of embryos derived from cryopreserved and fertilized oocytes has been established, which is relevant for both basic cryobiology and reproductive medicine in solving the problem of patient fertility preservation. The first polar body transfer from the recipient oocyte to the enucleated cryopreserved donor oocyte has been developed, it allows to preserve the nuclear genotype of the patient's oocyte and to increase the pregnancy rate in the group of patients with oocyte dysmorphism. Practical significance consists in the fact that the obtained results can be used in reproductive medicine and biotechnology researches. An application area covers the use in the treatment of infertility by the methods of assisted reproductive technologies, in learning programs of educational institutions for the training of specialists in various fields of biology, in particular of embryology, cryobiology, genetics and reproductive biology.