INFERTILITY DIAGNOSIS

Aneuploidy Detection using FISH (fluorescent in-situ hybridization) involves determining the percentage of sperm cells that have an abnormal number of chromosomes.

Aneuploidy means the gain or loss of one or more chromosomes compared to the amount there should be and is the main cause of miscarriage, learning disabilities, abnormal development and infertility. A high percentage of aneuploidy in the sperm is connected to abnormalities in the sperm analysis, the generation of aneuploid embryos and the failure of assisted reproduction techniques.

Aneuploid embryos rarely get past the first stages of early development and only some aneuploidies are compatible with life, (e.g. trisomy 21, trisomy 13, trisomy 18, triple X, XXY, XYY and monosomy X). Apart from monosomy X, monosomies tend to be more damaging than trisomies and they are rarely implanted. Therefore, it is important to assess nulisomies in the sperm that could cause monosomies in the embryo, resulting in a failed implantation. Our experience with PGD shows that certain chromosomes (16, 22, 15, 17) are often detected with embryonic aneuploidy; it is therefore logical to study them in the gametes, and Sistemas Genómicos is a pioneer in bringing them into the FISH study on the sperm cells.

FISH (fluorescent in-situ hybridization) is a cytogenic technique that allows us to mark chromosomes to be studied with a fluorescent probe so that we can identify them in each sperm cell analysed. Sistemas Genómicos has a  Metacyte-Metafer automated image capture system from Metasystems which allows us to analyse the different fluorescent signal patterns from the FISH in an automated, precise and reproducible way.

Automated analysis enables us to:

• Analyse up to 10,000 sperm cells per sample, generating greater statistical potential for the results.
• Carry out simultaneous analysis of up to 3 chromosomes in the same sperm nucleus, allowing us to detect disomies, diploidies and nulisomies with full guarantees – not guaranteed in manual analysis.
• Obtain better reproducibility, removing subjective variability from manual analysis.
• Reduce analysis time, analysing a greater number of sperm cells and chromosomes.
• Relocate each nucleus analysed to be assessed manually.

The DNA fragmentation study allows us to determine the percentage of sperm cells that have any breaks in the DNA (fragmentation index).

In infertile/subfertile males, a higher fragmentation index in sperm chromatin is connected with lower quality embryos and a low implantation rate, as well as sub-par results in assisted reproduction techniques.

Here at Sistemas Genómicos, DNA fragmentation studies are carried out with a direct method, the TUNEL technique(Terminal deoxynucleotidyl transferase dUTP nick end labelling). Unlike indirect methods, (SCD, SCSA), based on estimating the DNA’s susceptibility to denature, the TUNEL technique allows us to directly mark the breaks in the sperm DNA obtaining a result with greater predictive value regarding the fertilisation potential of the sample.

The abnormal chromosome segregation study allows us to determine the percentage of sperm cells that follow the normal meiotic pattern for the chromosomes involved in a certain chromosome rearrangement.

The carriers of chromosome rearrangements present different segregation patterns in the meiosis which creates normal gametes and gametes that carry the chromosome rearrangement. The percentage of abnormal gametes can change according to the aetiology of the rearrangement and the chromosomes involved, causing implantation failure, aneuploid embryos and/or repeated miscarriages.