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In-Depth Information
into a knee, uncured, it would squish away into nothing. When Danny, Larry,
and I showed our irst batch of printed sheep cartilage to a bunch of practic-
ing surgeons, they quickly ushered us out of the room once they igured out
that the printed cartilage was too weak to maintain even simple sutures.
Researchers are looking for solutions to this problem. One promising
method is to place artiicial tissue into a bioreactor to mimic the way real tissue
is pounded into maturity. To prepare bioprinted cartilage for real use, maybe
the solution will be provided by advances in hydrogel materials. Another pos-
sible solution may be the creative application of other sources of stress (such
as light or heat or sound vibrations) to prepare embryonic bioprinted cartilage
for what lies ahead. Yes, even cartilage needs tough love.
Printing heart valves
Cartilage may be a relatively simple type of living tissue but even some kinds
of cartilage are more complex and critical than others. For example, if the
cartilage in your knee or elbow is destroyed, you continue to live on (albeit
immobilized and in pain). However, if the cartilage in your heart valves isn't
doing its job, your risk of dying from some sort of cardiovascular disease
increases by 50 percent.
There's no organ more mission critical than the heart. The heart is made up of
muscle, blood vessels, and cartilage that dance together in a complicated routine
that's choreographed by electrical impulses that shoot through the body. The
average human heart beats nearly 100,000 times per day. In fact, heart tissue
withstands its own form of pounding, at an average rate of about 80 million
beats a year, about 5 to 6 billion beats in an average lifetime.
One of the most medically problematic parts of the heart are its thin ibrous
valves. The human heart has four chambers that are separated by valves. Heart
valves are like one-way gates that open and shut in precise time to control the
direction of blood low as it pumps from chamber to chamber. If these valves
don't work properly, a patient's heart will eventually fail. The American Heart
Association reports that ive million Americans each year learn they have heart
valve disease; defective heart valves are a common birth defect.
Heart valves are quite small, anywhere from between the size of a dime in a
newborn to the size of a quarter in an adult. Blood low must pulse hard in only
one direction. If a heart valve is mechanically inadequate, it will start to slowly
leak, sort of like an incompetent employee in an organization whose shoddy
