Two research teams in the last two months have published studies on kidney structures grown from stem cells, which might be a step toward personalised replacement organs grown from patients' own cells.
"We have converted skin cells to stem cells and developed a highly efficient process to convert these stem cells into kidney structures that resemble those found in a normal human kidney," biologist Ryuji Morizane of Brigham and Women's Hospital, lead author of a new study in the journal Nature Biotechnology, said in a statement.
Earlier this year, a team of Australian medical researchers lead by Minoru Takasato also succeeded in growing nephron organoids from stem cells in the lab. They published their results in the journal Nature.
Certain chemical signals can trigger stem cells to develop into specialised cells, or differentiate. In recent years, scientists have discovered ways to induce stem cells to differentiate into heart, liver, nerve, and pancreas cells. To grow kidney structures, Morizane and his team used genetic techniques to develop skin cells into stem cells, which they then developed into what are called "precursor cells," a type of stem cell that's only partially differentiated. These precursor cells developed into kidney cells and assembled themselves into structures that looked much like those found in real, live kidneys.
The results of their work are organoids, three dimensional organ structures grown in a lab, which are very similar to kidney structures called nephrons. Morizane and his colleagues published their work in the journal Nature Biotechnology.
Nephrons are the basic working structures in you kidneys; they filter excess water, salts, and harmful substances out of your blood and turn them into urine. Each kidney has about a million nephrons, which sounds like a lot — but it's a finite supply. Once you lose nephrons to disease or injury, your body can't replace them.
You Could Grow Your Own Kidney Transplant... Someday
That's what happens to patients with chronic kidney disease, for instance. Between 9% and 11% of adults in the U.S. are gradually losing kidney function to chronic kidney disease caused by diabetes, inflammation, infection, or other problems. For most of these patients, the best options are dialysis and, in some cases, kidney transplants.
Donor kidneys are in short supply, however, and transplants come with some risk. Morizane and his colleagues hope that their research will be a step toward one day growing replacement kidneys from patients' own cells - and idea that has long been a popular theme in discussions about stem cell research. They have grown nephron-like structures, not whole kidneys, but Morizane says it's a step in the right direction.
"We're hopeful that this finding will pave the way for the future creation of kidney tissues that could function in a patient and eliminate the need for transplantation from a donor," said Morizane in a statement. If it comes to pass, such a breakthrough could help doctors and patients work around the short supply of donor organs, and it could make transplants less dangerous for patients. One of the biggest challenges of organ transplantation - besides finding a compatible donor in the first place - is keeping the body from rejecting the new organ as a foreign invader. A kidney grown from the patient's own cells wouldn't set off the immune system's alarms, so rejection wouldn't be an issue.
New Tools for Studying Kidney Disease
Of course, that optimistic future is still a long way off. In the short term, these lab-grown organoids are more likely to help researchers study kidney development and test new drugs for safety and effectiveness.
Many drugs used to treat diseases elsewhere in the body are harmful to the kidneys, whose role in filtering harmful substances out of the blood leaves them especially vulnerable to toxicity. Organoids like those developed by Takasato's team and Morizane's team could give medical researchers a new way to test new drugs' effects on kidney structures in the lab.
They could also help create working models of kidney diseases in the lab, on which medical researchers could test potential treatments.
Because the development of these organoids from stem cells is so similar to the development of real kidney structures during gestation, they also offer a good way for researchers to study how kidney abnormalities develop in the womb, which could one day lead to better treatments or even prevention.
Top image: Ryuji Morizane, Brigham and Women's Hospital