Preimplantation Genetic Diagnosis (PGT) Applications has previously been used as a diagnostic tool for identifying genetic problems in embryos; however, it can now be used as a method of treatment as well. Embryo HLA Typing can be described as the most common method of treatment in PTD applications.
In childhood diseases that can specifically treated with stem cell transfers from the bone marrow or cord blood, Embryo HLA Typing can be performed using In Vitro Fertilisation and PGD in order to get embryos with In Vitro Fertilisation under the right conditions. If the embryos have a hereditary transferable disease and have compatible tissues with siblings who need stem cell transplantation, HLA compatibility is tested and then the embryo is transferred to the womb. Stem cells obtained from the cord blood post birth or bone marrows can be used to heal the sick sibling via transplantation. This approach is called HLA Typing.
Used for many couples all over the world, the HLA Typing method allows couples with genetic diseases to have healthy children as well as help treat sick siblings. The Embryo HLA Typing Method is becoming more common, primarily for diseases which can be treated with stem cell transplants such as Thalassemia, Leukaemia, Fanconi Anaemia, Wiskott-Aldrich Syndrome. Since finding suitable donors in these cases can be extremely rare, it is possible to treat the sick sibling with HLA typing, thus saving their life in the process.
In order to do Embryo HLA Typing, cell samples must be taken from embryos and in order to get cell samples from embryos, In Vitro Fertilisation must have been performed while getting the embryos.
Since it is not possible to monitor the development of the embryo in normal pregnancies, HLA Typing must be done at the earlier stages of pregnancy.
HLA Typing Process
Embryo HLA Typing is a multi-stage process that cannot be performed in isolation and needs to be done alongside In Vitro Fertilisation.
The stages can be summarised as:
- Preparation stage, in which blood or tissue samples from the couple and the sick child are taken to prepare for a genetic procedure on the embryo level.
- The couples are taken into In Vitro Fertilisation after preparation,
- The embryo is obtained after collecting eggs with an egg development programme and the sperm from the spouse to inseminate the eggs,
- The embryos are then examined for HLA compatibility (within the scope of genetic disease) with the sick sibling for stem cell transplantation,
- After the examination, healthy embryos are transferred to the womb to achieve pregnancy,
- In ideal conditions, the genetic preparation stage takes around 2-4 weeks, while the In Vitro Fertilisation process, obtaining embryo and genetic analysis of the embryo followed by the transfer into the womb takes about 3 weeks.
The success rate of the treatment is dependent on the number and quality of the eggs obtained during In Vitro Fertilisation and whether there are any genetically compatible embryos during the genetic examination.
In theory, 25% of the examined embryos are expected to be HLA compatible with the siblings. This rate drops to 18% in existing single gene disorders. These rates are “usual” rates. Finding compatible embryos and becoming pregnant might be significantly different for each couple.
Stem cells obtained from cord blood during this type of pregnancy and healthy birth or bone marrow after the baby develops to a certain degree can be used in the treatment of the sick sibling.