A6. Stem Cells in Medicine Flashcards
Stem cell therapies in existence - Bone marrow transplants
Bone marrow contains ____ ____that can become specialised to form any type of _______ ____. Bone marrow transplants can be used to replace the faulty bone marrow in patients that produce ____________ ______ _____. The stem cells in the transplanted bone marrow divide and specialise to produce healthy blood cells.
This technique has been used successfully to treat ____________(a cancer of the blood or bone marrow) and ___________(a cancer of the lymphatic system). It has also been used to treat some _________ __________, such as (2 things)
Bone marrow contains stem cells that can become specialised to form any type of blood cell. Bone marrow transplants can be used to replace the faulty bone marrow in patients that produce abnormal blood cells. The stem cells in the transplanted bone marrow divide and specialise to produce healthy blood cells.
This technique has been used successfully to treat leukaemia (a cancer of the blood or bone marrow) and lymphoma (a cancer of the lymphatic system). It has also been used to treat some genetic disorders, such as sickle-cell anaemia and severe combined immunodeficiency (SCID).
Stem cell therapies of the future
As stem cells can divide into specialised cell types, scientists think they could be used to replace damaged tissues in a range of diseases. Scientists are researching the use of stem cells as treatment for lots of conditions, including:
(5 things)
- Spinal cord injuries - stem cells could be used to replace damaged nerve tissue.
- Heart disease and damage caused by heart attacks
- stem cells could be used to replace damaged heart tissue.
- Bladder conditions - stem cells could be used to grow whole bladders, which are then implanted in patients to replace diseased ones.
- Respiratory diseases - donated windpipes can be stripped down to their simple collagen structure and then covered with tissue generated by stem cells. This can then be transplanted into patients.
- Organ transplants - organs could be grown from stem cells to provide new organs for people on donor waiting lists.
Sources of stem cells
To use stem cells scientists have to get them from somewhere.
There are three main potential sources of human stem cells:…? (with description)
- Adult stem cells
- Obtained from the body tissues of an adult. For example, adult stem cells are found in bone marrow.
- Can be obtained in a relatively simple operation-with very little risk involved, but quite a lot of discomfort.
- Adult stem cells aren’t as flexible as embryonic stem cells - they can only specialise into a limited range of cells, not all body cell types (they’re multipotent). Although scientists are trying to find ways to make adult stem cells specialise into any cell type.
- Embryonic stem cells
- These are obtained from embryos at an early stage of development.
- Embryos are created in a laboratory using in vitro fertilisation (IVF)— egg cells are fertilised by sperm outside the womb. Once the embryos are approximately 4 to 5 days old, stem cells are removed from them and the rest of the embryo is destroyed.
- Embryonic stem cells can divide an unlimited number of times and develop into all types of body cells (they’re pluripotent).
- Induced pluripotent stem cells (iPS cells)
- iPS cells are created by scientists in the lab. The process involves ‘reprogramming’ specialised adult body cells so that they become pluripotent.
- The adult cells are made to express a series of transcription factors that are normally associated with pluripotent stem cells.
- The transcription factors cause the adult body cells to express genes that are associated with pluripotency.
- One of the ways that these transcription factors can be introduced to the adult cells is by infecting them with a specially-modified virus. The virus has the genes coding for the transcription factors within its DNA.
- When the virus infects the adult cell, these genes are passed into the adult cell’s DNA, meaning that the cell is able to produce the transcription factors.
Ethical considerations (4 things)
- Some people believe that at the moment of fertilisation an individual is formed that has the right to life-so they believe that it’s wrong to destroy embryos.
- Some people have fewer objections to stem cells being obtained from egg cells that haven’t been fertilised by sperm, but have been artificially activated to start dividing. This is because the cells couldn’t survive past a few days and wouldn’t produce a fetus if placed in a womb.
- Some people think that scientists should only use adult stem cells because their production doesn’t destroy an embryo. But adult stem cells can’t develop into all the specialised cell types that embryonic stem cells can.
- This is where induced pluripotent stem cells could prove really useful. They have the potential to be as flexible as embryonic stem cells, but, as they’re obtained from adult tissue, there aren’t the same ethical issues surrounding their use. It’s also possible that iPS cells could be made from a patient’s own cells. These iPS cells, which would be genetically identical to the patient’s cells, could then be used to grow some new tissue or an organ that the patient’s body wouldn’t reject (rejection of transplants occurs quite often and is caused by the patient’s immune system recognising the tissue as foreign and attacking it).
Benefits of stem cell therapy (3 things)
- They could save many lives-e.g. many people waiting for organ transplants die before a donor organ becomes available. Stem cells could be used to grow organs for those people awaiting transplants.
- It might even be possible to make stem cells genetically identical to a patient’s own cells. These could then be used to grow some new tissue or an organ that the patient’s body wouldn’t reject.
- They could improve the quality of life for many people-e.g. they could be used to replace damaged cells in the eyes of people who are blind.
