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School Biology notes: Cell specialisation 5. Use of stem cells in medicine

Cell specialisation: 1. The use of stem cell technology, particularly in medicine

Doc Brown's GCSE level Biology exam study revision notes

There are various sections to work through, after 1 they can be read and studied in any order.

Sub-index for notes on stem cells, cell differentiation and cell specialisation

(5) The potential uses of stem cells, particularly in medicine

Cells from early human embryos and adult bone marrow, called stem cells, can be made to differentiate into many different types of cells, e.g .nerve cells - so have the potential to be converted into any type of cell found in the human body.

However, whereas early embryonic stem cells can differentiate into any type of specialised cell, adults only have stem cells in a few places like bone marrow and these can only turn into a few types of cell e.g. blood cells.

Since human stem cells have the ability to develop into any kind of human cell, they have great potential for use in treating certain medical conditions.

Reminder: As the embryo develops, the stem cells divide, producing more stem cells, but also differentiated cells - the process of differentiation in which cells for a specific specialised function are produced e.g. cells for skin, organ tissue, blood cells etc.

Transplanting stem cells or transplants of specialised cells grown from stem cells can potentially help with certain medical conditions

It is possible to extract stem cells from early human embryos and adult bone marrow and reproduce (growing) them under different particular conditions so that they differentiate into particular types of specialised cells.

After growing the embryonic stem cells you can then stimulate them to differentiate into specialised cells for use in further research or medical applications - treatments.

In the laboratory you can produce clones of stem cells - genetically engineered identical cells.

Doctors are already using stem cells to cure some diseases e.g. sickle cell anaemia can sometimes be cured with a bone marrow transplant containing adult stem cells that produce new red blood cells.

In the UK there is a shortage of blood donations to give sick patients blood transfusions, so it is hoped that sufficient artificial blood can be created using stem cells.

Another possible source of stem cells is blood left in the umbilical cord and placenta after a baby is born. Cord blood is easy to collect and store. It also avoids the ethical issues involved with using stem cells from embryos.

These embryonic stem cells can be used to treat various medical conditions such as replacing diseased damaged tissue or tissue damage from injury e.g.

initiate new nerve cell connections for people paralysed by spinal injury e.g. treatment with stem cells may be able to help conditions such as paralysis and it is hoped to be able to grow nerve cells for people disabled by a spinal injury.

transplant new cardiac/heart muscle cells to replace tissue of people suffering from heart disease,

insulin-producing cells for diabetics,

treating conditions in which certain body cells degenerate, especially with ageing e.g. Alzheimer's disease, diabetes and multiple sclerosis.

treating leukaemia - replacing rapidly produced abnormal white cells with normal healthy cells (more on this below),

cancer or following treatments for cancer like chemotherapy or radiation e.g. patients suffering from leukaemia,

blind patients have had there sight restored with stem cell treatment by treating the part of the eye responsible for central vision.

Quite simply, there is huge potential from stem cell research and application to alleviate many medical conditions, which up to now, have been very difficult to treat - hence the huge scientific interest in the potential for new cures - but such strategies are not without risks and hot debates on the ethical issues involved.

It is hoped that in the future large scale storage banks of stem cells can be created so as to be readily available for clinicians to treat many medical conditions.


Treating leukaemia (leukemia)

Leukaemia is a type of cancer found in your blood and bone marrow and is caused by the rapid production of abnormal white blood cells.

These abnormal white blood cells are not able to fight infection and impair the ability of the bone marrow to produce red blood cells and platelets.

Adults have stem cells in their bone marrow but these can only be converted into a few specific type of cells - so only quite limited specialisation is possible.

The stem cells in the bone marrow are important in replacing dead cells e.g. producing new red blood cells.

Leukaemia is a cancer of the blood or bone marrow.

Leukaemia can be successfully treated using stem cell technology.

You may have heard the phrase 'bone marrow transplant' - this involves treating a patient with a supply of healthy stem cells to differentiate into specific healthy cells to replace damaged or faulty cells e.g. in this case, blood cells.

A stem cell or bone marrow transplant is a gene therapy procedure that involves replacing damaged bone marrow with healthy bone marrow stem cells.

It isn't a transplant of an actual organ like a lung or heart, but the blood system can be considered as a tissue system.

A stem cell transplant involves destroying any unhealthy blood cells and replacing them with stem cells removed from the blood or bone marrow.

The bone marrow contains the stem cells that become specialised to form any type of blood cell, so the transplanted bone marrow produces the healthy blood cells.

A stem cell transplant can involve taking healthy stem cells from the blood or bone marrow of one person ideally a close family member with the same or similar tissue type and transferring them to another person.

Stem cells in bone marrow produce three important types of blood cells : red blood cells which carry oxygen around the body, white blood cells which help fight infection and platelets which help stop bleeding.

Bone marrow transplants are not only used to treat sufferers of leukaemia, but also patients with non-Hodgkin's lymphoma and sickle cell anaemia.

A stem cell transplant has 5 main stages. These are:

  1. Tests and examinations to assess your general level of health

  2. Harvesting the process of obtaining the stem cells to be used in the transplant, either from you or a donor

  3. Conditioning treatment with chemotherapy and/or radiotherapy to prepare your body for the transplant

  4. Transplanting the stem cells

  5. Recovery

Stem cell transplants also enable chemotherapy patients, whose bone marrow has been destroyed by the anti-cancer chemicals, to produce red blood cells again.

It is hoped one day to culture stem cells in huge quantities and produce stem cell lines from patients with rare and complex diseases that can potentially transform treatments in a health service.

At the moment the number of stem cell therapies is quite limited, but it is hoped to be able to stimulate stem cells to differentiate into a much wider range of tissues - the process is called transdifferentiation.


Therapeutic cloning

One of the latest developments is called therapeutic cloning.

Therapeutic cloning involves producing stem cells with the same genes as the patient.

Because they are genetically have the same genes, they shouldn't be rejected by the patient's immune system.

An embryo can be modified to have the same genetic information as the patient.

This means these stem cells have the same genes and less likely to be rejected by the patient's body.

Therapeutic cloning involves nuclear transfer.

1. The nucleus is removed from a human egg cell.

2. The nucleus of a body cell from the patient is transferred to the egg cell from which the nucleus was removed.

3. The modified egg cell is stimulated to divide and cause an embryo to grow.

4. After 4-5 days the stem cells are removed from the embryo and cultured to produce enough to treat the patient.

(The embryo is discarded)

Summary of learning objectives and key words or phrases

Be able to describe and explain the potential uses of stem cell treatments in medicine including sickle cell anaemia, treatment, regenerating diseased or damaged tissue, leukaemia treatment transplants and therapeutic cloning.



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