Researchers have created a working kidney that's able to produce urine when transplanted into a rat, according to a new study.

The bioengineered kidney wasn't entirely built from scratch — rather, the new organ was built around an existing kidney “scaffold.”

While much more work is needed to see if the same technology could be used to engineer human kidneys, the researchers hope that eventually, such a method could be an option for those who have kidney failure, and need a new kidney.

“If this technology can be scaled to human-sized grafts, patients suffering from renal failure who are currently waiting for donor kidneys, or who are not transplant candidates, could theoretically receive new organs derived from their own cells,” said study researcher Dr. Harald Ott, of the Massachusetts General Hospital Center for Regenerative Medicine. Building kidneys using this technique could the risk that the organ would be rejected, he said.

To make the kidney, the researchers first removed kidneys from rats and treated them with a detergent solution that stripped all living cells from the organ, leaving only a scaffold of fibrous proteins. Then, the researchers built a new kidney around the scaffold, using human umbilical cord cells and kidney cells from newborn rats. To disperse the cells onto the scaffold, the researchers created a pressure gradient that “sucked” the new cells into the right place in the kidney, Ott said.

The bioengineered kidneys grew in chambers that contained nutrients to simulate the inside of the body. Then, the kidneys were transplanted into rats that had one of their kidneys removed. [Video: See how the kidneys were made ]

Once the bioengineered kidneys were given a blood supply, they worked to filter blood and produce urine. However, they did not work as well as the rats' natural kidneys, so the technique needs to be refined, the researchers said.

Previously, researchers have shown a similar scaffolding technique can work to create bioartificial hearts. While the researchers in the new study did not engineer a human kidney, they did show that human kidneys could be stripped down to a scaffold. Theoretically, these scaffolds could then be “seeded” with human stem cells to grow the kidney, the researchers said.

The study is “certainly a major step forward in organ regeneration,” said Jeremy Mao a biomedical engineer and professor at Columbia University in New York City, who was not involved in the study.

As it stands, the technique can't create a new organ from scratch, so donor kidneys would still be required for transplants. However, because the living cells are stripped out of the bioengineered kidneys, the tissue matching between donors and recipients that is currently required for transplants may not need to be as rigorous, Mao said.

And because the bioengineered kidneys could potentially be created using patients' own cells, there could be less of a chance of organ rejection, and patients may not need to use drugs to suppress their immune systems, Mao said.

The new study is published today (April 14) in the journal Nature Medicine.

Pass it on: Researchers have engineered a working rat kidney.

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