Scientists have long assumed that once a tissue runs out of stem cells, the damage is permanent. New research out of Israel suggests otherwise. The body may be able to turn back the clock on its own aging cells, converting them into fresh stem cells to repair itself from within.
Researchers found that mature, aged cells in the cornea can revert into active stem cells to regenerate damaged tissue—a previously unknown way the human body heals itself.
A key trigger, they found, is the immune system: macrophages, cells normally deployed to fight infection at injury sites, also release signals that prompt aged cells to become stem cells again. If scientists can learn to harness and control this natural process, it could eventually reduce the need for transplants in treating conditions that cause blindness, disability, or chronic disease.
Reprogramming Cells for Self-Repair
Live tracking showed that the stem cells, located at the edge of the cornea, normally divide about twice a week, creating new cells that slowly move toward the center of the eye’s surface as they age.
The researchers studied how mature cells in the eye can revert to a stem cell state by completely removing the native limbal stem cell area—the outer ring of the eye where stem cells usually live in mice.
Removing the stem cell area forced the eye to repair itself using only the remaining mature corneal cells, testing their ability to adapt. Researchers found that mature cells changed their molecular profiles to resemble those of healthy stem cells, indicating true cellular reprogramming.
A key player in this process is the immune system—especially immune cells called macrophages. These cells arrive at injury sites to prevent infection and release signals that trigger the rejuvenation of aged cells into stem cells.
Shalom-Feuerstein added that the repair process involves mature, aged cells being reprogrammed into stem cells that can function for many years and prevent disease.
This kind of regenerative capacity was previously thought to be limited to simple organisms that can regrow limbs, but the new findings suggest complex animals—mice, and potentially humans—retain some of that ability, too.
While most of the discovery was based on experiments with living mouse models to trace and track cells, the researchers also used primary human corneal epithelial cells in laboratory studies to validate their findings.
When they applied the same cytokines from macrophages to mature human corneal cells grown in a dish, these cells also developed more stem-like qualities, showing that the biological pathway responsible for cell reversal is the same in both species.
Even with no stem cells left, the tissue recovered, forming an entirely new population from cells that were never stem cells to begin with. The mature, aged cells were reprogrammed by macrophage signaling into stem cells capable of functioning for years afterward, he said.
Future studies need to be done to see if other mature cells can also be reprogrammed into stem cells, researchers said. It is the first study to show that mature cells can also revert to their earlier states, they said.
Implications for Eye Treatments
The cornea renews itself from a small reserve of stem cells that sit at its border in a region called the limbus.
When those stem cells are lost to a chemical burn, a severe infection, or a genetic condition, the cornea cannot resurface itself and vision clouds over.
Today, that kind of damage is treated with a stem cell graft or transplant. Both options depend on donor tissue or tissue from the patient’s other eye, which presents the problem of supply and rejection, Dr. Krishna Surapaneni, a board-certified ophthalmologist and cataract, cornea, and refractive surgeon at SuraVision in Houston, and not involved in the study, told The Epoch Times.
“A regenerative approach that reactivates the eye’s own repair cells could, in principle, sidestep both problems at once,” Surapaneni said, “Because there would be nothing foreign to reject and nothing to harvest from a second site.”
The longer-term hope, he added, is prompting a patient’s own remaining eye cells to step into the stem cell role and rebuild the surface themselves, rather than replacing it with tissue from elsewhere. “That would be a meaningful shift, because it works with the eye’s own biology instead of relying on a limited supply of donor material.”
A Reason for Optimism
Surapaneni called the findings “genuinely exciting,” but noted this is still largely a mouse study, with only early, encouraging signals in human cells in the lab. Researchers are now investigating whether the same natural regeneration process exists in humans, and how it might eventually be harnessed.
“The gap between a mechanism working in mice and a safe, reliable treatment for patients is wide,” Surapaneni said. “And it is measured in years, not months.”
Still, the study challenges the assumption that once a tissue loses its stem cells, the decline is a one-way street. “If mature cells can be coaxed back into a repair role, that reframes how we think about healing in the eye and possibly beyond it,” Surapaneni said.
Toxins and Metabolic Stressors Can Impede Process
Oxidative Stress: Tobacco smoke, pesticides, heavy metals, and radiation can trigger oxidative stress that damages DNA, proteins, and cell membranes, creating genomic instability that makes it harder for a cell to reset itself.
Epigenetic Changes: Stem cell reversion requires a cell to erase its epigenetic “memory” of its mature identity. Prolonged exposure to harmful chemicals, metabolic byproducts, and chronic inflammation can alter a cell’s epigenome in ways that lock it into its current state.
Cellular Waste Buildup: Poor metabolic health combined with toxic exposure can cause a buildup of fat droplets and misfolded proteins. When a cell’s waste-removal systems become overwhelmed, the renewal process needed to become a stem cell can stall.
