Ask
the doctor: Does exercise help damaged heart muscle?
Q. After
my heart attack, my doctor told me that damaged heart muscle cannot be
replaced. If this is true, why am I walking on a treadmill five days a week? Is
this helping repair the heart muscle damage or strengthen what's left of my
heart muscle?
A. Your
skeletal muscles can repair themselves after an injury — pull your calf muscle
and, after a few days or so, it heals. Until recently, it was believed that the
human heart didn't have this capacity. But the heart does have some ability to
make new muscle and possibly repair itself. The rate of regeneration is so
slow, though, that it can't fix the kind of damage caused by a heart attack.
That's why the rapid healing that follows a heart attack creates scar tissue in
place of working muscle tissue.
how to repair heart muscle damage
Vigorous
exercise can help repair damage from heart attack
Vigorous daily exercise can repair damage caused due
to a heart attack by activating dormant stem cells, leading to the development
of new cardiac muscle, according to a new study.
Scientists had already discovered that stem cells
could be coaxed into producing new tissue through injections of chemicals known
as growth factors, but the new study is
The Daily Telegraph reports that “vigorous daily exercise
could repair damage caused by a heart attack”.
It has long been known that the heart muscle can
increase in size in response to regular exercise increasing its workload. This
has been thought to just be due to the existing heart muscle cells getting bigger.
However, this new study has found that in healthy
adult rats, this increase in size is also, in part, due to the generation of
new heart muscle cells from dormant stem cells in the heart tissue.
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The researchers also identified some of the proteins
that appear to be prompting this cell generation.
As this was a study in rats with healthy hearts it
is not yet clear whether exercise has the same generative effect in in humans,
or in damaged heart tissue.
If these findings are to be harnessed to develop new
treatments for humans, this is most likely to involve using the proteins that
the researchers have identified to prompt dormant stem cells into action. Tests
of this approach have been started in animals, and these will need to be
successful before any tests could begin in humans.
Where did the story come from?
The study was carried out by researchers from
Liverpool John Moores University and the Magna Graecia University in Italy. It
was funded by the British Heart Foundation, the European Community, the
FIRB-Futuro-in-Ricerca program, and the Italian Ministry of Health.
The study was published in the peer-reviewed European
Heart Journal.
The Telegraph reports that this research is early
stage, and was in rats. While rats and humans share many biological
similarities, there are also – self-evidently, some important differences.
So, while the news report suggests that the findings
may apply to humans with heart muscle damage, it is not yet clear whether this
is the case.
What kind of research was this?
This was animal research assessing whether exercise
might induce heart stem cells to produce new heart muscle cells.
It is known that if an animal does a lot of
exercise, its heart muscle increases in size to cope with the increased
workload.
This was thought to be due to the existing heart
muscle cells getting bigger, and the researchers wanted to investigate whether
new heart muscle cells might also be being made from the stem cells that exist
in adult heart tissue. Stem cells are essentially biological “building blocks”
that have the ability to develop into a wide range of specialised cells,
including heart muscle cells (myocytes).
As humans and other animals share many aspects of
their biology, findings from animal studies give researchers an idea about how
human biology may work. However, these hypotheses do need testing, as there can
be differences between the species.
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What did the research involve?
The researchers exercised male adult rats on a
treadmill for 30 minutes a day, four days a week for up to four weeks. They
also had a group of similar adult male rats that were not exercised.
They then looked at the effect of the exercise
programme on heart tissue, and particularly the stem cells in their heart
tissue.
This included looking at whether new heart or blood
vessel cells were being made by the stem cells.
They also looked at how any changes to the stem
cells might come about by looking at whether growth factor proteins were being
produced by the existing heart tissue that could be prompting the stem cells to
become active.
What were the basic results?
As expected, the researchers found that, in response
to the exercise programme, the rats’ heart muscles got bigger, due in part to
the existing heart muscle cells getting bigger. However, they also found that
new heart muscle cells had been formed, with about a 7% increase in the number
of heart cells seen in the rats that did the highest-intensity exercise.
New capillaries (small blood vessels) also formed to
increase blood flow to the new heart tissue.
The researchers found that there was an increase in
the number of stem cells in the hearts of the exercised rats, although the
number decreased after the first two weeks of exercise. This was suggested, in
part, to be because they had developed into new heart muscle or capillary
cells, and in part because the heart had adapted to its new workload. The stem
cells in the exercised rats had increased activity of genes, which lead to them
developing into heart muscle or capillary cells.
The researchers found that the existing heart muscle
cells in exercised rats produced more of a certain group of growth factor
proteins than they did in control rats. Exposing heart stem cells in the
laboratory to these proteins made the stem cells divide more, and start down the
pathway of development of heart muscle and capillary cells. This suggested that
these proteins might be what are inducing stem cells to produce more heart
muscle cells and capillary cells in the hearts of the exercised rats.
How did the researchers interpret the
results?
The researchers concluded that intensity-controlled
exercise training prompts heart muscle remodelling both through increasing the
size of existing heart muscle cells, and by leading to differentiation of heart
stem cells into new heart muscle cells and capillary cells.
They say that these findings highlight the
“regenerative capacity of the adult heart” provided by the heart stem cells,
and identify proteins which could potentially be used to induce regeneration
and repair in damaged heart tissue.
Conclusion
These findings suggest that, at least in adult rats,
exercise can lead heart stem cells to become active and generate new heart
muscle and capillary tissue.
This challenges the previous view that change in
heart muscle size in adult animals in response to exercise is only a result of
the increasing size of existing muscle cells.
The study has investigated the effects of exercise
in healthy rats, and it is not yet clear whether exercise would have the same
effect in rats with heart muscle damage.
If the findings are to be harnessed to help treat
human heart muscle damage, this is most likely to involve using the proteins
that have been found to prompt this regeneration.
The authors of the paper report that further animal
research into this possibility is ongoing.
This animal research will need to show positive
results before any such new treatments could be tested on humans.
