Regenerative medicine, which works with stem cells and DNA, is on track to cure Parkinson’s disease, diabetes, and even age-related blindness.
The story of stem cell therapies includes such unlikely plot twists as human hearts grown in pigs and a kidney 3-D printed from living cells on the TED stage. In 2017, stem cells made a spinach leaf beat like a human heart. But some regenerative medicine is much more down-to-earth.
Many people associate stem cells with embryos, yet science has advanced to the point where stem cells can be produced from adult cells. Read on to learn how that works and what it means for people in need of a cure.
Cosmic Time Machine
The gold standard in regenerative medicine is growing brand-new tissues and
organs using a patient’s own DNA. Scientists can turn adult skin cells back into stem cells and use them to grow new tissues and organs. Patients are less likely to reject organs made from their own DNA, so there’s no need to use embryonic stem cells.
Until recently, scientists thought that cells only changed in one direction: from general to specific. This idea is at the heart of developmental biology; embryos start as generic blobs of stem cells that are all the same. Those stem cells quickly transform into neurons, blood vessels, skin, muscles, bones, and organs.
Returning adult cells to their embryonic state is like giving them a ride in a cosmic time machine.
But in 2007, we learned that cells could change in the other direction. Nature published an article on how scientists in Japan had reprogrammed adult skin cells to become stem cells. The resulting cells, called iPS cells, function just like embryonic stem cells. iPS cells can specialize into any kind of tissue. To create iPS cells, researchers inserted only four genes into a skin cell. Shinya Yamanaka of Kyoto University won the Nobel Prize in 2012 for this discovery.
Restoring Vision in Old Mice
Yamanaka’s discovery can be used in other ways than creating stem cells. Researchers at Harvard Medical School recently found a way to reprogram cells to a ‘younger’ state. The Harvard team used the same four genes that Yamanaka used to turn skin cells into iPS cells. But they only left the genes turned on for a few days. Adult mouse cells reverted to a younger state but didn’t go all the way back to stem cells—young, but not too young. It’s as if the scientists hit “rewind” on a movie, but instead of returning to the opening title, they resumed the film half-way through.
Once the Harvard team turned back the clock on the cells, the cells regained the ability to repair themselves. Old mice that had lost their eyesight regenerated retinal nerves and regained their vision.
Stem Cells and Parkinson’s
Research is underway at the Texas Biomedical Institute to treat Parkinson’s disease with stem cells. By turning skin cells into stem cells, scientists can grow healthy brain cells that produce the dopamine missing in Parkinson’s patients. And the cells would carry the patient’s own DNA.
Stem Cells and Diabetes
Even though iPS cells share stem cells’ powers, some regenerative therapies still use embryonic stem cells. The biotech company Viacyte is in clinical trials to treat diabetes using pancreatic cells created from embryonic stem cells. The use of iPS cells to treat diabetes has been tried in primates but has not reached the human clinical trials. It’s possible Viacyte and other companies will be able to use iPS cells in the future.
In Viacyte’s approach, the cells are placed in small artificial capsules and inserted under the skin. Each capsule becomes a free-standing miniature pancreas, generating insulin so diabetics don’t need injections. The capsules can easily be removed if anything goes wrong. The fine mesh of the capsules allows sugar and insulin to pass through. But it blocks large immune cells, which might otherwise attack the new pancreatic cells.
Creating a Hybrid Immune System
Scientists have developed a novel way to prevent the rejection of transplanted organs. It involves mixing stem cells from the organ donor with those of the organ recipient. This creates a hybrid immune system, so the recipient’s immune system accepts the donor’s organ as its own. In a recent clinical trial, 80 percent of recipients were able to forego antirejection drugs 14 years later.
These are just a few examples of how regenerative medicine offers possible solutions for chronic diseases and other severe conditions.