TOKYO, Sept. 22 (UPI) -- A kidney grown in a lab was successfully connected to the excretion systems of rats and pigs, allowing the organ to function and grow properly, researchers report in a new study.
The researchers said they are years away from attempting to implant a lab-grown kidney in a human, however the proper function of one in an animal is a big step toward that goal.
Currently, people with kidney failure can undergo dialysis but there are limits to how long it can continue.
"Worldwide, the number of patients with end-stage renal disease requiring renal replacement therapy is increasing because of the shortage of donor organs," researchers wrote in the study, published in the Proceedings of the National Academy of Sciences. "We have successfully generated functional kidneys from human stem cells using the organogenic niche method."
The researchers reported that while they can grow functioning human kidneys from stem cells, there is no way for the organs to excrete the urine they generate.
In order to work around this, the researchers grew a section of pig kidney using metanephroi, or cells from an embryonic pig fetus, in the lab. It grew and produced urine, eventually succumbing to hydronephrosis because it could not excrete the urine.
The researchers then found a way, in rats, to construct a pathway for urine to travel from the lab-grown kidney out of the body by developing rat metanephroi with bladders that had been developed from cloacas. Once the kidneys were implanted in rats, the cloaca-derived bladders were connected the animal's actual bladder, allowing urine to leave the body.
The method, which researchers call a "stepwise peristaltic ureter," was then successfully demonstrated in pigs, as well, where the kidneys functioned, grew and the animals were able to urinate.
"This is an interesting step forward," Chris Mason, a professor at University College London who was not involved with the research, told the BBC. "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."