20 the heart, it is no surprise that there

20 people
in the United States die every day waiting for an organ transplant. The
national transplant list has over 116,000+ men, women, and children as of
August 2017, and this number is only growing. Further, 20,000 people in the
United States require a transplant, but only 2,000 people donate hearts
yearly.  This discrepancy means that even
with the medical knowledge to save a patient’s life, doctors cannot do so because
not enough organ donors can support the growing patient population. Although educational
initiatives through public education campaigns such as Donate Life America and
Youth Education on Organ and Tissue Donation exist to raise awareness of the
healthcare issue, progress is slow and the organ donation shortage problem
persists.

 

However,
with the advent of medical technology, biomedical engineers are breaking ground
in the field of stem cell research and regenerative medicine. Currently, the
tools to develop artificial organs, particularly an artificial heart, are being
developed. If we progress to a point where physicians could transplant a
completely manmade heart into a patient, engineers will have provided a
permanent solution to the fatal organ shortage problem in the United States.

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The idea
in and of itself is foreign – the heart is central to the body. Humans
associate life itself with a beating heart, and some may argue that it is the
heart that makes us human. However, this central organ can be constructed by
scientists in a lab. The heart beats around 60 times a minute, every minute of
a person’s life. Considering the constant strain on the heart, it is no
surprise that there is a clinical need to have replacement hearts in case of
heart failure. It could revolutionize the boundaries of medicine – bioengineers
would be creating life, as there is no human life without a beating heart. The heart
is complex and dynamic and capable of pumping the life force through the body,
and responding to natural cues my slowing or quickening the pulse. Thus, an
artificial heart must not only mechanically pump blood through the body; it
must also react to the microenvironment around it to emulate the complexity of
a natural organ.

 

One of the
techniques to engineer the heart involve 3D printing. Thus far, researchers
have printed a soft artificial heart that functions similarly to a natural
heart. Many challenges pose scientists in this initiative, as compounds such as
metal and plastic are difficult to mesh with natural tissue. One way to resolve
this issue is to use silicone ventricles that move like a real heart, but even
with 3D printing, the entire structure is one compartment with a chamber that
fills and empties to pump the “heart” (Cohrs et. al, 2017).  This structure only has two ports where the
blood flows in and out, and worked effectively. However, the artificial heart
would only last thousands of beats, or 45 minutes, and wouldn’t support a patient
over the course of a lifetime. The tensile strength of the material with which
the 3D printed artificial heart is made must be increased in order to be a real
candidate for implantation into a patient.

 

 

 

 

 

 

A separate
approach involves tissue engineering that creates a heart personalized to the
patient via stem cell manipulation. The current technique to engineer the heart
goes as follows. Physicians remove the heart from a newly deceased individual
(that does not necessarily have to be human) and remove the cells with a
chemical solution that dissolves all but a natural protein scaffold. They seed
the scaffold with stem cells that are personalized to the patient receiving the
organ. In theory, this engineered heart could grow and adapt with the patient
post-operation. Performed seamlessly, this seemingly simple procedure could
revolutionize medicine, not just providing a patient with a heart to continue living
a healthy life, but also to erase the problem of organ donor shortages that hospitals
struggle to reconcile.

 

Researchers
have been able to derive contractile heart cells from stem cells on a Petri
dish for over a decade. By shocking the cells with an electrical signal, the
cells have been proven to be able to beat for hours. CITATION

 

The
complex network of capillaries that supply the heart with oxygen and nutrients
and remove waste is extremely difficult to recreate with synthetic materials –
first in terms of construction and also integration into the human body. Vascularity
is a challenge

 

The upside
to engineering from a protein scaffold is that we could use the hearts of other
developed animals such as pigs, who have very similar structure and vasculature
to a human heart. The extracellular matrix of a pig heart emulates that of a
human and would not be weakened by the constant strain of beating throughout a
lifetime, unlike a completely artificially constructed heart made of synthetic machinery.

There is also a limitless supply of pig hearts, thus erasing the issue of organ
donor shortage.

 

The
challenge with this approach is that a chemical detergent is required to strip
away molecules specific to a pig that may trigger an immune rejection from the
human patient. Adding too much detergent will wash away essential proteins and
growth factors  

 

 

Balance –
don’t use so much detergent that you strip away too much material from the
donor heart

 

 

It begins
with acquiring the cells to seed into the protein scaffold. Scientists must
consider the cardiac cell regeneration potential. The cells must grow and
duplicate in a test tube on a large, organ-level scale, integrate with the
original heart tissue, and develop into new heart cells when electrically
coupled with the host heart tissue. This complex process is long and provides
many opportunities for mistakes to occur along the way.