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:
-
Tests and examinations –
to assess your general level of health
-
Harvesting – the process
of obtaining the stem cells to be used in the transplant,
either from you or a donor
-
Conditioning – treatment
with chemotherapy and/or radiotherapy to prepare your body
for the transplant
-
Transplanting the stem
cells
-
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)
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.
