Scientists in the US have developed a kit designed to mend torn membranes in heart muscles. Liposomes or little bundles of fat are coming in handy in achieving The patch work
INDIA, a frontrunner as far as the incidence of heart attacks is concerned, will
have to import the technique of mending damaged hearts. The repair kit, called
'cellular bandage', meant to seal holes in
the heart occuring after an attack, was
recently developed by researchers in the
us (New Scientist, Vol 148, No 2004).
Developed on the basic understanding of hole creation that disruption of
blood supply to cells creates holes in the
outer membranes, forcing them to die,
scientists at the Boston-based North-
eastern University developed this novel
patching technique. "Cell death occurs
because the holes in the membrane
allow critical enzymes and salts to wash
out of the cells," says Ban-An Khaw, the
leader of the research team.
When a person experiences a heart
attack, the blood supply to the heart
muscle is terminated, creating holes in
the membrane of the cells. The chances
of survival of any victim of a heart attack
depends on the extent to which his or
her heart muscle has incurred damage
by the same. Scientists, therefore, set out
to investigate if the damage sustained by
the heart muscle could be limited by
patching up the holes in time.
Interestingly, the patching technique involves little bundles of fat called
liposomes, which are already being
tested as a delivery system for drugs and
genes. The liposomes in this case are
coated with antibodies which are
designed to bind with myosin. Myosin is
a protein found in abundance inside the
cells of the heart muscle, responsible for
contraction of the muscle. Scientists
believed that the affinity between the
antibodies on the liposomes and the
myosin inside the cell will draw the liposomes over holes in the cell's membrane. Antibodies would thus anchor
liposomes into the gaps where they
would eventually blend with the cell
membrane containing fat.
The next step was to test this theory,
Cultured heart muscle cells were first
starved of oxygen. Following this, half of
them were treated with liposomes and
the other half were left untreated. The
number of cells that survived were to
indicate whether or not liposomes sealed
holes. Significantly, with liposomes,
almost 90 per cent of the oxygen starved
cells survived. Without liposome treatment, just five per cent survived.
To trace how the cells got sealed,
scientists used silver grains trapped
inside the liposome molecules. "If the
silver stays on the outside of the cells, we
know they have been plugged. But if the
silver grains end up inside the cells, the
liposomes must have fused with the cell
membrane," says Khaw. Further, by
plugging the cellular holes and restoring
blood supply by giving standard clot
busting drugs, one could salvage up to
90 per cent of the heart muscle.
After successful laboratory trials,
animal trials are on the anvil.
While heart attack victims are sure to
benefit from this technique, could the
wonder kit seal broken hearts as well?
Time will tell.
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