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Transplant breakthrough as researchers reveal working kidney grown in the lab from stem cells

Researchers used used rats as incubators for the growing tissue
Kidneys were generated from stem cells and were first tested in pigs
Human trials still several years off, say researchers

Published: 18:02 EST, 22 September 2015 | Updated: 18:54 EST, 22 September 2015

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Scientists say they are a step closer to growing fully functioning replacement kidneys after a breakthrough in results in animals.

They used rats as the incubators for the growing embryonic tissue.

Although still years off human trials, the research helps guide the way towards the end goal of making organs for people, say experts.

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Growing kidneys: Four weeks after transplantation, the authors connected one of the host rat’s ureters to the transplanted bladder. Eight weeks after transplantation, the kidney tissues contained structures characteristic of mature kidneys, the team said.

THE KIDNEY CRISIS

According to the National Kidney Foundation, over 100,000 Americans are currently in need of kidney transplants

Most sit on the waiting list for an average of 3.6 years before finding a match.

In 2014, 17,105 kidney transplants took place in the US.

Of these, 11,570 came from deceased donors and 5,535 came from living donors.1

Over 3,000 new patients are added to the kidney waiting list each month

The kidneys were generated from stem cells and were first tested in pigs.

The researchers recently succeeded in growing functional kidneys from human stem cells, but these kidneys are unable to grow to full size because they have no pathway for excreting urine, resulting in a condition called hydronephrosis.

To solve this issue, Takashi Yokoo and fellow Jikei University School of Medicine researchers added a drainage pathway and compatible bladder to connect everything to the animal's existing bladder – a technique they call 'Stepwise peristaltic ureter' or SWPU system.

'The SWPU system may resolve two important problems in the generation of kidneys from stem cells: construction of a urine excretion pathway and continued growth of the newly generated kidney,' wrote the researchers in the journal PNAS.

The method worked in rats, even when checked eight weeks later, so the researchers went back to test on pigs, which also proved promising with the new method.

The next step is to conduct much more extensive research to see the long term effects these stem cell-generated kidneys have on the body.

Takashi Yokoo and colleagues developed a potential solution to this problem by implanting embryonic rat kidneys with bladders into adult rat hosts.

'Four weeks after transplantation, the authors connected one of the host rat’s ureters to the transplanted bladder,' the journal said.

'This approach allowed the urine from the transplanted kidneys to pass into the transplanted bladder and then into the host bladder, thereby avoiding hydronephrosis.

'Eight weeks after transplantation, the kidney tissues contained structures characteristic of mature kidneys.'

When they connected up the new kidney and its plumbing to the animal's existing bladder, the system worked.

Scientists say they are a step closer to growing fully functioning replacement kidneys after a breakthrough in results in animals - but stressed human trials still several years off.

Urine passed from the transplanted kidney into the transplanted bladder and then into the rat bladder.

To test the clinical feasibility of this system, called the stepwise peristaltic ureter (SWPU) system, the authors repeated the experiments using pigs and achieved results similar to those observed in rats.

Prof Chris Mason, an expert in stem cells and regenerative medicine at University College London, told the BBC it may still have problems:

'This is an interesting step forward,' he said.

'The science looks strong and they have good data in animals.

'But that's not to say this will work in humans. We are still years off that. It's very much mechanistic. It moves us closer to understanding how the plumbing might work.

'At least with kidneys, we can dialyse patients for a while so there would be time to grow kidneys if that becomes possible.'