- One major challenge of organ transplantation or stem cell transplantation is the lack of donors.
- This is due to mismatch in what is called as HLA factor.
- Scientists have found a group of genes that code for proteins that help our immune system to recognize self and identify foreign bodies. These proteins are called HLA and every cell of our body has about a lakh of them.
- HLA match is important in stem cell and organ transplantation.
- It so happens that HLA match is best among same-sex siblings. Even between parents and offspring, there is no suitable HLA match.
- In short, when the HLA match is absent the immune system rejects organ transplanted.
Note: To find healthy donors for stem cell transplantation, a database called National Stem Cell Registry is maintained in India.’
Autologous, Allogenic and Xenogenic transplants
- In the context of organ or stem cell transplantation, depending on its source, donor cells plantation can be classified as
- Autologous: Cells from one’s own body (including stem cell therapy, iPS cells etc)
- Allogenic: Cells from another’s body but of same species
- Xenogenic: Cells from another species.
- With advancements in gene editing techniques, gene therapies and Xenotransplantation are seen as the potential alternatives to supply organs for transplantation.
- However, the major challenge is immune reaction from the human recipient.
Organ transplantation from one species to another is called xenotransplantation.
Need for Xenotransplantation
- While autologous is the best method (as there won’t be immune rejection), making iPS cells takes a lot of time.
- Allogenic is good when there are suitable donors.
- Given the shortage of donors with HLA match scientists have been increasingly working on Xenotransplantation as animals like pigs with lower lifespan can be bred to grow human organs.
- Gene editing in pigs to reduce immune rejection has made organ transplants from pigs to humans possible, which could offer help to thousands of people who face organ failure, disease, or injury.
- The natural lifespan of a pig is 30 years, they are easily bred and can have organs of similar size to humans.
Recent steps by India in stem cell transplantation
Thalassemia Bal Sewa Yojna
- Hematopoietic Stem Cell Transplantation (HSCT) program was launched in 2017.
- Hematopoietic Stem Cell: These are cells present in bone marrow.
- They are undifferentiated stem cells capable of developing into all types of blood cells, including white blood cells, red blood cells, and platelets.
- Eligibility: Only patients whose monthly family income is below Rs 20,000 will be eligible for this assistance.
Bone marrow transplantation
Stem cell cure for blindness
- Recently a medical college from Kanpur claimed the 1st cure blindness through stem cell transplants.
Mitochondrial DNA and Nuclear DNA
- The DNA we have been referring to is the DNA that is present in the nucleus
- In addition to DNA in the nucleus, some DNA is also present in the mitochondria.
- During fertilization it is the nuclear DNA (with 46 chromosomes) that is formed where 23 chromosomes is inherited from the mother and 23 from the dad.
- Mitochondrial DNA only has one chromosome and it codes for only specific proteins responsible for metabolism.
- It is the nuclear DNA that is responsible for inheritance (from both father and mother).
- Mitochondrial DNA is inherited only from the mother and thus it is more effective to trace human ancestry.
Three parent baby
- Apart from receiving the usual “nuclear” DNA from its mother and father, the embryo would also include a small amount of healthy mitochondrial DNA from a woman donor.
- This is resorted to when the actual mother is suffering from an incurable mitochondrial disease.
- This technique involves removing the faulty mitochondrial DNA from the actual mother and nucleus form the mother’s egg and the resultant egg fertilizes with the sperm cell of the father outside the body (in-vitro).