20 January 2014

Ghost organs: the future of transplant medicine?

The human body is far from perfect, being at risk from numerous degenerative diseases that 'break' essential organs and lead to our deaths. Aging, disease and poor lifestyle choices are the obvious causes of such organ failure and our current level of science and technology is largely unable to cure such damage.

Organ transplants provide patients with the best hope of survival, in which the defective organ is replaced by a healthy one from a donor. Needless to say, such operations are dangerous and carry high risks of patients' dying during the operation, from the patient’s own body rejecting the new organ and secondary infections (caused by post-surgery immunosuppressant drugs).

Last year, 166 people in the UK went under the knife in heart transplant operations [source]. Needless to say such operations are dangerous and, despite recent advancement in aftercare treatments, 1 in 10 patients will die within the following year. Their body rejecting the new organ is the main cause of these deaths, which kills most patients within the first month from the surgery.

Yet despite the risks thousands of people are on transplant waiting lists all over the world, being desperate for the chance of getting a replacement organ to extend their lives. Improvements in operation procedures and aftercare have reduced the risk of dying during surgery in recent years, but rejection is still a major issue that patients must consider and is something that we are unable to prevent in every case.

Transplanted organs are rejected by leukocytes (white blood cells), which make up our body's natural immune system. All cells have proteins on their surface called antigens, which allow leukocytes to identify 'friendly' tissues. Foreign material has different antigens on its surface which, when detected by leukocytes, causes them to destroy the invading cells. This is usually beneficial and allows us to 'fight off' bacteria and viruses, but in organ transplants the donor actually needs the foreign material to live!

Anti-rejection drugs (which suppress our immune system), have had some success in preventing rejection, but they put the patient at risk of dying from common illnesses (such as colds and intestinal bugs) and aren't successful in all cases. The perfect solution to this problem would be to clone the patient’s organ so their body doesn't recognise it as 'foreign’ material' post-transplantation. But - thanks to all of the media’s unfounded nonsense and scare-mongering about stem cell research - our cloning technology is still a long way off being able to do this. We do have something similar in the pipeline though – ‘ghost’ organs.

This sounds ridiculous, right? But actually it’s not and a ghost organ is simply an organ that has been decellularized. Chemicals that are commonly found in detergents and shampoos are used to ‘wash away’ all of the organ’s cells until only a ‘scaffolding’ of extracellular connective proteins are left. Healthy cells are then taken from the patient and are grown over the connective proteins to repopulate the organ. Once this repopulation process is complete, the donor has a heart comprised of their own cells so rejection is EXTREMELY unlikely!

This is a ghost organ made from a decellularized pig's heart. All of the cardiac cells have been stripped away, leaving only the connective tissue.

If perfected, ghost organs have the potential to be transplant’s equivalent of cancer's 'magic bullet' and may save uncountable human lives in the future. But, despite having repopulated ghost organs with cells successfully, the technology still has its problems and scientists must find a way to make the cells functional if they are to used as replacement organs.

For example, the cells in ghost hearts beat discordantly as individuals, which means they would only pump half the fluid as a healthy heart around a host's body. Obviously, this means they aren't viable for transplants yet and scientists must devise a way to get them to pump in a propagated wave (as healthy heart cells do), before they will be of any medicinal use!

But prominent researchers in this field, such as Dr Doris Taylor from the University of Minnesota, are optimistic and predict that human trials will likely begin taking place in years rather than decades! Ghost lungs are proving to be particularly successful and research is progressing in using ghost organs to replace almost the entire human viscera!

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