One of the major hopes for future
years is the ability to engineer transplantable material in a laboratory, which
may well reduce the need for organ donation and better yet, reduce the risk of
rejection since the organs can be engineered to have the recipient’s cells (and
thus the correct HLA). Being able to make an organ in a lab using a patient’s
own cells sounds like something out of science fiction but it is fast becoming
science fact. Early last year a team lead by Korkut Uygun were able to
engineer a rat liver in a lab. This was achieved by taking a liver and
stripping it of all its living cells. This left a framework for the correct
structure of a liver to which the team were able to add a whole new set of
hepatocytes (the major cell type that makes up the liver). Think of this like
drawing a stick man then adding detail to it to draw a cartoon person. The
hepatocytes that were added were produced from stem cells taken from the
recipient rat meaning the team produced a (semi) functional liver with the
correct HLA for the recipient rat. Impressive as this work is, it still has
some way to go before being of real clinical use. For starters, livers aren’t
only made of hepatocytes and the work was only on a small rat liver, but it is
no doubt an incredibly exciting prospect. Another approach for engineered
organs was successfully used only a few months ago in which a patient
received a windpipe transplant. The interesting thing about this transplant was
that the windpipe framework was made of a completely synthetic material, which
was then coated in the recipient’s cells. Hats off to the surgeon Paolo
Macchiarini and the producer of the synthetic material Alexander Seifalian (a
researcher at UCL I’d like to add) for this pioneering work.
Not only could we one day produce
organs in a lab but we may also be able to use animal organs, a procedure known
as xenotransplantation. This isn’t without its complex issues as you can
imagine, not least in terms of different organ sizes but some organs do hold
hope (pig hearts and our hearts, for example, are of very similar size and
structure). Being able to use animal organs would certainly avoid the issues of
a shortage of available organs but whether people will accept the idea of
receiving a pig heart is yet to be seen. The safety of such procedures is also
unclear as there may be a risk of zoonosis (the link is back to an older blog I
wrote about HIV in which I discuss zoonosis).
Another bright hope for the
future is the ability to induce immunological tolerance (another topic I will
write a blog on in the near future) to the new tissue. As I mentioned above,
our immune system is highly tuned to be able to detect our specific HLA, but
when the cells of our immune system are first produced they all have different
receptors for binding to the HLA, obviously not all will be able to. The cells
must therefore learn how to bind to the correct HLA, and any cells unable to
will be destroyed. If we could find a way to make the immune cells recognise
the new tissue as self (make the cells tolerant to the new tissue) it would
avoid the whole issue of rejection.
One final thought would be for regenerative medicine (a link to a small article with more detail on regenerative medicine). This is in its early days but centres around the potential use of
stem cells to repair damaged tissues which potentially could one day be used to stop the
need for transplantation entirely.
Transplantation is not without
its issues but the work in the area has an incredibly bright future and the
power to have an astonishing impact on many people’s lives. One problem that
may be encountered however is with funding. A major source of funding in the
medical realm comes from the big pharma companies. However, these companies
make huge profits from transplant patients who have to continue taking (and
buying) drugs for the rest of their lives and there may therefore be reluctance
to find ways around the issue of avoiding rejection which, in turn, may make
funding hard to come by (something I hope not to be the case). Still, the
future looks bright for the world of transplantation.
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