For the first time, scientists have successfully grown functioning human kidney tissue in the lab that is able to produce urine. The kidney tissue, generated from human stem cells, was implanted under the skin of mice and went on to develop into working kidney cells.

Millions of people around the world every year either die from kidney disease, or undergo dialysis while waiting for a transplant. This remarkable advance brings medicine one step closer to being able to either repair or replace damaged kidney tissue in human beings by growing a functioning organ from stem cells.

The milestone study was led by researchers from the University of Manchester and started by growing microscopic parts of the kidney, called glomeruli, in a Petri dish using human pluripotent stem cells. This stage had been previously achieved by other researchers, but it was the next step that pushed the team's work into truly novel territory.

These kidney cells were then subcutaneously implanted into mice that had been engineered to lack a functioning immune system. Twelve weeks later, the tissue had successfully grown to reveal nephrons, the structural elements found inside a working human kidney. As well as developing a network of blood vessels, the kidney structures were shown to be producing a urine-like substance called glomerular filtrate.

"We have proved beyond any doubt these structures function as kidney cells by filtering blood and producing urine – though we can't yet say what percentage of function exists," says Sue Kimber, one of the lead researchers on the project. "What is particularly exciting is that the structures are made of human cells which developed an excellent capillary blood supply, becoming linked to the vasculature of the mouse."

Sheila MacNeil from the University of Sheffield, who was not affiliated with this research, commends the team for bridging an important research gap between growing human cells in a lab and actually getting them to develop into a functioning organ.

"This is a key step showing that the cells had the potential – what was needed was to give them an appropriate environment in which they could self organize," says MacNeil. "This study points the way to one day achieving growth of new kidneys to replaced damaged kidneys in patients."

Despite the significant milestone marked by this study, there is still an enormous amount of work to be done before we are able to regrow functioning human kidneys for use in transplants.

"Building on our generation of kidney filtration units we must now turn to developing an exit route for the urine and a way to deliver this technology to diseased kidneys," says Adrian Woolf, co-lead on the study with Sue Kimber.

The new study was published in the journal Stem Cell Reports.

Source: University of Manchester