EUPLOIDY – GENETIC ISSUES

In ART treatments, the aneuploidy of the embryo represents the major factor affecting the outcome, leading to spontaneous miscarriage or to several genetic disorders.

Even if the incidence of aneuploidy rises significantly with maternal age, most aneuploidy results from meiotic defects during the oogenesis and the fertilization process (chromosome segregation, translocation errors).

As soon as the very first minute of the fertilization process, very important biological events, critical for the future developmental competency of the embryo are taking place.

These biological events, after the sperm cell entry in the oocyte cytoplasm and prior to the first cleavage, include: the completion of the meiosis, the exclusion of the second polar body, the pronuclei formation, the replication of the male and female DNA and the chromosome segregation on the newly formed and highly unstable mitotic spindle.

If any of these events is aberrant, one or both of the two daughter cells and their descendants may carry chromosomal anomalies. In other words, an uneven first cleavage in size or in content is associated with chromosomal abnormality and aneuploidy.

Chromosome segregation errors, for example, are often irrespective of the fertility status or of the maternal age; their occurrence can be associated with several factors ranging from the oogenesis to exogenous factors including culture conditions (1-8).

The chromosomal fate of an embryo is likely determined prior to the first cell division, centered around the fertilization process, making these first hours of development a key stage of the human embryonic development.

With the Anecova Natural Fertilization procedure, this key development stage occurs in a natural environment where the presence of specific molecules and of a dynamic and physiological environment might be an advantage over in vitro culture conditions by limiting the source of possible stress, by ensuring optimal cellular functions and the mitotic spindle stability (9-13).

Preliminary data from the pilot study (14) have shown a higher proportion of euploid embryos for sibling oocytes cultured in vivo vs. in vitro (88.2% in vivo vs. 46.7% in vitro). In animal models, in vivo cultured embryos have been described with significant reduction of aneuploidies and also with differences in the gene expression levels patterns when compared to in vitro cultured embryos. Moreover, there is also growing evidence that the culture conditions of human pre-implantation embryos can affect the gene expression regulation with measurable effects on embryos and on newborn children (15-28)

We expect the Anecova Natural fertilization procedure to allow the development of a high proportion of euploid embryos with an enhanced developmental potential and with minimal genetic issues.

 

 

Glossary:

Aneuploidy: is the presence of an abnormal number of chromosomes in a cell, for example when having 45 or 47 chromosomes when 46 is expected in a human cell.

Mitosis: is a part of the cell cycle in which chromosomes in a cell nucleus are separated into two identical sets of chromosomes, and each set ends up in its own nucleus.

Meiosis: is a specialized type of cell division which reduces the chromosome number by half. This process occurs in all sexually reproducing single-celled and multi-celled eukaryotes. Errors in meiosis resulting in aneuploidy are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities.

 

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