An experiment for the repair of rat hearts has been successful and scientists are now declaring that this stem cell treatment could be applied to humans successfully.
The team of scientists, some of whom were from Geron, the California-based biotechnology company, under the leadership of Dr. Charles Murry, revealed in the September issue of Nature Biotechnology that when human heart muscle cells obtained from embryonic stem cells were implanted into rats after they had suffered heart attacks, the cells not only helped to rebuild the heart muscle but also improved the functioning of the heart.
The study was conducted at Geron Corp. in Menlo Park, and at the University of Washington School of Medicine in Seattle.
In their experiment the scientists first brought about heart failure in the rats. Then they used human embryonic stem cells to re grow their heart muscles four days after the heart attacks. Heart failure is caused when the arterial blood vessels become fuzzy as a result of which the cardiac muscle fails to supply blood.
The muscle fibers and the part of the heart which do not receive blood and oxygen breakdown and a scar is formed. This hinders the pumping of blood. In order to cure this, human embryonic stem cells were injected onto the external surface of the heart ventricles.
The researchers developed a new procedure that noticeably improved how stem cells were turned into heart muscle cells and then went on to survive after being implanted in the damaged heart of a rat. The findings suggest that stem-cell-based treatments may one day be used to help people suffering from heart disease, which is the leading cause of death in most parts of the world.
The scientists had two main problems to deal with when treating damaged hearts with stem cells. The first was the creation of cardiac cells from embryonic stem cells, and then seeing to it that those cells survived after they were implanted in a damaged heart.
Embryonic stem cells are capable of turning into any type of cell found in the body. But the researchers attempted and managed to get the stem cells to morph into just cardiomyocytes, or heart muscle cells. Earlier experiments had resulted in cell preparations in which less than 1 percent of the differentiated cells were cardiac muscle cells.
The scientists however suspended the stem cells in a biochemical cocktail of “survival factors” made up of growth-encouraging proteins. They then purified the cells. They were able to turn about 90 percent of the stem cells into cardiomyocytes. Every rat thus treated had their heart grew a human tissue graft, whereas only 18 percent of rats that received grafts without the 'cocktail' grew the human tissue.
In their follow up the scientists also found that the grafts helped thicken the walls that normally widen after a heart attack and weaken the heart. The thickened walls were then linked to more energetic contractions.
UW assistant professor of pathology and the lead author of the study Dr. Michael Laflamme said, "We found that the grafts didn't just survive in the rat hearts -- they also helped improve the function of the damaged heart, That's very important, because one of the major problems for people suffering a myocardial infarction is that the heart is damaged and doesn't pump blood nearly as well. This sort of treatment could help the heart rebound from an infarction and retain more of its function afterwards."
Geron is planning to use the findings to manufacture a medication for heart attacks.
Now that the scientists are sure that the procedure works on rats they are experimenting with sheep because the pulse rate and heart size are more or less the same as they are for human beings. The scientists are also planning to carry out tests on human beings should these experiments be successful Murry also said that early human clinical trials could begin with in the next two years.
