Currently, there are hundreds of
thousands of people on transplant lists all over the world, waiting for
critical organs like kidneys, hearts, and livers that could save their lives. I
was shocked to hear in a recent assembly that last year, over 400 people in the
UK died waiting for a vital organ transplant and a further 777 people were
removed form the waiting list due to deteriorating health that meant a
transplant was no longer a viable option. As it stands, in the UK, 5693
patients are waiting for a transplant and statistics show that in the USA every
10 minutes another person is added to the transplant waiting list, since
unfortunately, there aren’t nearly enough donor organs available to fill the
growing demand.
This got me thinking; in this
crazy and unprecedented world of modern research and development, surely there
is a solution to this problem?
And yes, there is.
Bioprinting is a branch of
regenerative medicine currently under development that has the potential
to create brand new, customised organs from scratch. Like modern 3D printing,
bioprinting is a technique that deposits layers of material on top of each other
to construct a 3D object one slice at a time, but instead of starting with
plastic or ceramic based inks, a 3D printer for tissues and organs uses bioink.
The main component of many bioinks
are water-rich molecules called hydrogels. Millions of living cells are mixed into
these, as well as numerous chemicals encouraging processes such as cell
communication and growth. Engineering an organ or tissue is dependent upon
having the right kinds of cells. In some cases, cells are isolated from a small
tissue sample the size of a postage stamp. They are then mixed with growth
factors and multiplied in the lab. The cells rapidly multiply in quantity so
that, in about 6 weeks, a layer one cell thick could theoretically cover a
football pitch. For cell types that cannot be substantially grown outside the
body (e.g. heart, nerve, liver and pancreas cells), stem cells may be an option
because of their pluripotency – the ability to become multiple cell types. Some
inks contain just a single type of cell, whilst others combine several
different kinds of cells, enabling scientists to create more complex
structures.
There are several printing
techniques utilised in this field, the most popular being extrusion-based
bioprinting. In this, bioink gets loaded into a printing chamber and pushed
through a round nozzle attached to a printhead. It emerges from a tiny nozzle to
produce a continuous fibre, the thickness of a human fingernail.
A computerised image guides the
placement of the strands, either onto a flat surface or into a liquid bath
that’ll help hold the structure in place until it stabilizes. After printing,
some bioinks will stiffen immediately; others need UV light or an additional
chemical or physical process to stabilise the structure. A successful printing
process means that the cells in the synthetic tissue will begin to behave the
same way cells do in real tissue: signalling to each other, exchanging
nutrients, and multiplying.
Most bioprinting uses a scaffold to
hold cells in place. And once cells are ‘coaxed’ to a certain level, they begin
to self-organise and assemble and then the scaffold can be removed. Dr Nakayama,
a doctor and chairman of Saga University’s Regenerative Medicine and Biomedical
Engineering department, has been developing a way to create 3D tissue without
the need for scaffolds. Instead, he mounts small spheres on a fine array of
needles called a kenzan and is now preparing the first human trial to implant
dialysis tubes made entirely from a patient’s own skin cells.
 |
3D bioprinting using a kenzen
rather than scaffolds
|
The technology in this field
already exists to print simple structures like lung tissue, skin, cartilage as
well as miniature, semi-functional versions of solid organs, including kidneys
livers and even hearts. Researchers have successfully used 15 different applications
of cell/tissue therapy technologies in human patients - including a bioprinted bladder
that was successfully implanted into 10-year-old Luke Massella in 2001.
Luke Massella was born with a condition
known as Spina Bifida, which left a gap in his spine. He is one of about 10
people alive walking around with a replacement bladder that has been grown from
his own cells. At age 10, a malfunctioning bladder caused his kidneys to fail, and
Luke faced a lifetime of dialysis treatment, that would have severely inhibited
him from living a normal life. An enterprising surgeon, Dr Anthony Atala at
Boston Children's Hospital, took a small piece of Luke's bladder, and over two
months grew a new one in the lab, then in a 14-hour surgical procedure he
replaced the defective bladder with the new one. In using the patient’s own
cells this way, the issue of organ rejection (when the body’s immune system attacks
transplanted cells from another organism) was minimised. Luke hasn’t had to
have any surgery since and now, at 27, lives without complication.
 |
| Scientists at Wake Forest IRM using bioprinting to develop a replacement bladder. |
However, replicating the complex
biochemical environment of a major organ is a harder feat, with so many more
cells per centimetre. One of the biggest challenges is how to supply oxygen and
nutrients to all the cells in a full-size organ and so the greatest successes
so far have been with structures that are flat or hollow. To try and overcome
this issue, researchers are working to incorporate blood vessels into the
printed organs.
Ultimately, bioprinting organs
from people's own cells will solve the huge lack of supply in organs for
transplant and eliminate the need for anti-rejection immunosuppressant drugs. Specialist
printers could even reproduce cancers tumours, giving doctors the chance to
test treatments on specific patients. Bioprinters also provide a way of testing
small quantities of fluid to test if a new antibiotic would work for a specific
patient - this could help tackle the growing and serious problem of
antimicrobial resistance.
The potential to use bioprinting
to save lives and advance our knowledge of organ function is huge. This kind of
technology also opens up the possibility of augmentations similar to those seen
in the classic science-fiction and superhero films, such as the printing of
tissue with embedded electronics or the engineering of organs that exceed
current human capability. Could we give ourselves futuristic qualities such as
unburnable skin? And to what extent might we extend human life by printing and
replacing our own organs when they start to fail with age?
References:
https://www.bbc.co.uk/news/business-45470799 https://www.ted.com/talks/taneka_jones_how_to_3d_print_human_tissue/transcript?language=en https://school.wakehealth.edu/Research/Institutes-and-Centers/Wake-Forest-Institute-for-Regenerative-Medicine/Research/ABCs-of-Organ-Engineering#Learn About the Steps Involved in Engineering Tissue and Organs
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