Image copyright Rex Features Image caption Sarah Tageres received her pig kidney around Christmas
A woman in Germany successfully received a kidney from a pig at the end of 2017.
The pig kidney was donated by a friend who was suffering from failing kidneys, and that kidney “was transplantable to a human patient”.
The successful test in 2011 sparked speculation that pig organs could be used to treat people with failing kidney function.
However the animal has now made headlines as the living kidney transplant has not yet been tried on a human patient.
The stem cells found in human embryos can then be turned into the ultimate solution for human kidney disease – and is the only way to be sure the patient is dying from cancer, not a form of kidney disease, experts say.
Image copyright Caroline and Chris Machir Image caption Caroline Machir said she thought she was experiencing signs of cancer
The reason for tests being carried out on the pig kidney is that when the stem cells are used to treat a condition such as cancer, there will be a small amount of loss of function in the cells that are involved in the process of transplanting living cells, such as the stomach and intestines.
The mice that the cells are injected into will then try to grow in size and gain weight, giving a first-hand experience of what happens when they develop cancer.
So far around 500 live pig kidneys have been transplanted between animals since 2009. The size of the transplants ranged from around 1kg (2.2lbs) up to 3kg.
Such a huge dose of pig cells mean that for a pig transplant to be successful on the recipient it would take a lot more pig organs than only the pig kidney donated to the woman, which was around two kilograms.
These pig kidneys could also be used for sheep, and other animals.
Jennifer Morrow, lead surgeon at University Hospital in Leeds, said: “The clinical need for transplantation of potentially live human organs from pigs, or members of their species, to live human recipients is very real.
“Although I have not performed a human pig kidney transplant myself, I have carried out liver transplantation with pigs on humans.”
Scientists first started experimenting with pig kidneys – both in the 1950s – with five such attempts, in fact. Although in the mid-1950s – at the beginning of nuclear testing – the chief organ donor was a cow, and a handful of pig kidneys were used in this way until the 1980s.
In recent years there have been many trials carried out where organs – including pig kidneys – have been used, “but they did not get past the trial phase”, meaning the transplant did not take place.
The people involved usually experience kidney failure because of a condition such as cancer, and end up needing dialysis treatments or a transplant.
Several times in recent years volunteers have been tested in a cocktail of kidney drugs, but what they have been given to potentially cure them has been the subject of controversy.
Many scientists regard transplanting a pig kidney as too experimental and say that has not stopped trials from taking place, while others are less confident in this treatment method.
So what would happen if pig kidneys were used to treat human kidney disease?
Most researchers think that a person with kidney disease is dying from the cancer.
Tests using stem cells taken from a person’s own bowel and stomach are already showing a successful treatment for this.
Doctors do not think that taking the stem cells from a pig has any potential as there are still some implications that these cells are not yet fully developed.
“It would be the only way to transplant a pig kidney successfully and without having to develop the pig cells from scratch,” said Dr Katharina Neubauer, spokesman for the German Society of Nephrology.
However, so far no trials have yet been done on human patients, and even if a trial were to take place it would not be able to fix everyone’s failing kidneys.
The biggest concern remains the levels of radiation involved – if transplanting hundreds of thousands of stem cells into a human is to work, there will have to be very small doses of radiation given to try to regenerate the cells and get them to grow to a certain degree.
The problem is that this process is generally not effective as rapid growth does not always happen – one previous study found that some cells tended to die because the stem cells were too weak to develop into a proper kidney.
But according to Dr. Neubauer, if the person receiving the pig kidney was a potential cancer patient, or someone with poor immune system, this could be a viable option.
“We see it as an alternative option in our final treatment programme,” she said.
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