Right now, kidney failure treatments involve hours spent hooked up to a dialysis machine, or a donor transplant – which are scarce. But there's hope of a new option in the not-too-distant future: an artificial kidney implant.

Scientists have developed a bioreactor device that uses human kidney cells cultured in the lab and mimics some of the key functions of a kidney. It's been successfully tested in pigs for a week with no obvious side effects or issues.

The team, led by the University of California, San Francisco (UCSF), is hopeful that their device can be adapted to include a broader range of kidney cell types and be paired with another instrument to filter waste from the blood.

"We are focused on safely replicating the key functions of a kidney," says bioengineer Shuvo Roy from UCSF.

"The bioartificial kidney will make treatment for kidney disease more effective and also much more tolerable and comfortable."

Kidney Project device
The new device is ready to be developed further. (University of California, San Francisco)

To give you an idea of the scale of the problem, over half a million people in the US alone require dialysis treatment several times a week. Only about 25,000 kidney transplants are carried out each year, and they often come with harsh drug treatments to ensure the new kidney isn't rejected by the body.

Crucially, there were no indications that the bioreactors had triggered the pigs' immune systems. The scientists fitted silicon membranes to help protect the kidney cells from attack and to keep the tiny machine working quietly and effectively in the background, much like a pacemaker for the heart, for example.

The device, which connects directly to blood vessels and veins, is made with cultured human proximal tubule cells; they're responsible for managing water and salt levels in the body and were used as a test case in this study. These cells have previously shown promise in treating kidney failure in human patients.

We're still a fair way from getting a bioreactor device like this working in human patients, of course, but the early signs are promising. Month-long trials in animals will come next, and if they are successful, the go-ahead should be given to start testing the device in actual people with kidney failure.

Scientists are also busy looking at other options, such as the viability of transplanting animal organs into human patients. No matter what the approach, the aim is the same: to save the lives of those with kidney failure.

"We needed to prove that a functional bioreactor will not require immunosuppressant drugs, and we did," says Roy. "We had no complications and can now iterate up, reaching for the whole panel of kidney functions at the human scale."

The research has been published in Nature Communications.