Sunday, 18 September 2011

Give Us A Hand (post 2 of 2)

I left the last post with the question of what work is being done to make transplantation safer and improve the availability of organs..?

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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