Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: nilmot on 30/09/2004 10:20:23
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For the lovely people whom also read NewScientist this might not seem new!
In the NewScientist last week it mentioned the possible chance of curing heart disease by use of stem cells. Not necessary stem cells from the embryo but stem cell from other part of body that is also present in adult.
Sources of stem cell present are:
- in the heart itself, which are used for repairs but there are very little.
- in bone marrow, which produced red blood cells and other immune system cells (now scientists are trying to do more testing, there has been a case when a patient recovered using this method).
- in skeletal muscle, which repairs itself if you have a muscle injury. (more testing is required as the skeletal muscles are different from cardiac muscles and could cause problem with rhythm of the heart as it contracts).
What's interesting is these stem cells are not actually blank in the same way as embryonic stem cells, which are totally blank and can form into anything. These are sort of 'semi-specialise', the scientists are experimenting this method on larger organs to see if it has the same effect. Some people say that it is way to early to use this method in humans.
I'll read some more of the article as it is 4 pages long.
Tom
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It would be interesting to know what kind of heart disease the stem cells could 'cure' - presumably not atheromatous coronary heart disease.
More likely in heart failure, where the heart muscle itself is stretched and 'flabby', so no longer able to contract efficiently. Could these cells cause new heart muscle to grow, and would that help to increase the pumping efficiency of the myocardium ?
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It's for when the dead heart muscle becomes scar tissues and they have to be removed by mean of surgery that the stem cells can compensate for that lost of heart muscles. So yes most likely heart failures, with coronary heart disease it is to do with the blood vessels rather than the heart itself so probably not.
Tom
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Heart attacks occur when the blood supply to a region of the heart muscle is interrupted, usually because the artery becomes blocked by a blood clot forming on a patch of atheroma (arterial disease).
The muscle supplied by the obstructed vessel rapidly becomes starved of oxygen and, unless the blood flow is restored rapidly (called re-perfusion), that patch of muscle will die. The damaged piece of heart muscle breaks down and is replaced by firm, stiff fibrous tissue, which can't contract and hence cannot contribute to cardiac function.
The loss of muscle tissue makes the heart weaker, so the surviving muscle compensates for the loss by increasing its workload (and becoming larger). Obviously there are limits to this ability to compensate, and sometimes the degree of damage is so large that the heart cannot maintain sufficient output. Under these circumstances a patient is said to be in heart failure which is, quite literally, the failure of the heart to keep up with the demands of the body.
The idea behind stem cell therapy for myocardial infarction (heart attack) is that undifferentiated (unspecialised) stem cells can be encouraged to turn into heart muscle cells and help to replace some of the muscle lost during the heart attack.
In initial trials in animals and humans, doctors have been gratified to see better outcomes (in terms of superior cardiac function) amongst stem cell recipients, compared with untreated cases.
However, the success of this therapy is probably more subtle than merely the replacement of lost muscle cells. Stem cells can contribute a huge range of cell types to an injury site. Only recently scientists found that when we cut ourselves bone marrow derived stem cells turn up in the wound site and turn into a variety of cell types concerned with repair and wound healing.
Stem cells introduced to the heart post-MI (myocardial infarct) could be acting in many ways, in addition to replacing some of the lost muscle. For instance they could secrete various growth factors which promote muscle survival and growth in the surrounding cardiac muscle, they may secrete vasogenic (blood-vessel forming) factors which help to boost the production of new blood vessels and hence blood supply to the surviving muscle, and they might help to reduce the scarring (fibrosis) caused by heart attacks, so that the heart can pump more effectively.
As work in this field progresses, these mechanisms will become much clearer. But it's certainly encouraging and exciting, particularly since one person in every 3 who reads this will, at the moment, ultimately die from heart disease.
Useful links about heart disease and stem cells :
What causes heart disease / arterial disease ?
http://www.thenakedscientists.com/HTML/articles/article/katarneycolumn8.htm
Article about stem cells and related links :
http://www.thenakedscientists.com/HTML/articles/article/chrissmithcolumn2.htm
University of Birmingham pages on vascular disease :
http://medweb.bham.ac.uk/http/depts/path/Teaching/foundat/athero/athero.htm
Radio show featuring Martin Raff all about stem cells :
http://www.thenakedscientists.com/html/shows/2003.10.12.htm
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Thank you Chris for clearing the problem
Tom
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Yes a great post. But how would the stem cells actually be placed into the myocardial environment - eg by injection ?
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Curiosity *may* have killed Schrödinger's cat
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That's right.
Several studies have now been carried out, initially in rodents (rats and mice) and latterly in pigs (which are viewed as a much better physiological approximation to humans).
In some studies stem cells (from a variety of sources but usually bone marrow) are infused down the coronary artery (which supplies the heart muscle). From there one presumes that the stem cells migrate into the affected tissue and promote revascularisation, repair and possibly themselves differentiate into muscle cells.
In the recent announcement from Johns Hopkins in the US looking at pigs, the researchers injected about 200 million mesenchymal (bone marrow derived) stem cells directly into the heart muscle. They accessed the heart by threading a fine cannula up an artery and into the left side of the heart. The cannula was then able to inject the cells into a coin-sized region of the heart recently damaged by a heart attack. A control group of pigs received injections with saline alone (no cells).
The pigs were followed up for 2 months. All of the animals that received stem cell injections made a full recovery and showed normal cardiac function. But the pigs in the control group deteriorated and developed congestive cardiac failure.
Furthermore, examination of the injected pig hearts revealed that those injected with stem cells showed reduced fibrous scarring in the heart muscle at the site of the infarct (heart attack) compared with the control pigs which showed large scars typical of heart disease.
At the moment we treat acute MI (myocardial infarcts) by accessing the blocked coronary artery, opening up the blockage with a balloon, and then propping the vessel open with a metal stent which works a bit like scaffolding to stop it furring up again.
Perhaps soon we will begin to see patients returning to the cath lab for injection of stem cells (from their own bone marrows, or perhaps even from banked cord blood - see my article about umbilical cord blood stem cells and stem cell banking) (http://www.thenakedscientists.com/HTML/articles/article/chrissmithcolumn2.htm) into their ventricular walls post MI.
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx