When Prof. Ruby Shalom-Feuerstein's team at Technion in Israel removed every single stem cell from the clear outer layer of mice's eyes, they expected the tissue to break down permanently. That didn't happen. To their surprise, the cornea — the part of the eye that lets in light — healed itself anyway.
The discovery, published in the journal Nature Communications, found that ordinary eye cells don't just sit idle after injury. Instead, they "turn back time," reverting into stem cells that can grow into fresh, healthy tissue. Stem cells are the body's raw material — cells that haven't yet decided what to become, ready to develop into whatever tissue needs fixing.
Scientists previously believed that once stem cells were gone from a tissue, the damage was irreversible. Treatments would require transplanting cells from outside the body. But the Technion team found the body has another trick up its sleeve. "What is even more surprising is the repair process itself," said Shalom-Feuerstein. "Following injury, even mature, aged cells undergo reprogramming and become stem cells that function throughout life."
The researchers used a clever labeling system with fluorescent colors to track what was happening inside the transparent corneas of living mice. They watched as immune cells called macrophages — the same cells that fight bacteria at wound sites — sent chemical signals that triggered the transformation of ordinary cells into stem cells. These newly formed stem cells didn't just patch things up temporarily. They kept working for long periods, enabling lasting repair.
This could matter a lot for human health. When stem cells in the cornea are damaged, people can lose their sight or even go blind. If doctors could activate the body's internal repair mechanism, they might be able to heal eyes without transplants. "Instead of relying solely on transplants or external interventions, we may one day be able to activate natural mechanisms that already exist within the body," Shalom-Feuerstein said.
The team has already seen encouraging results when testing the process on human corneal cells in the lab. The next step is figuring out how to control and harness this mechanism for medicine. "This is a first step toward understanding a natural process that until now was unknown to us," Shalom-Feuerstein said. "The next challenge is learning how to control it and how to use it for regenerative medicine."
The study was conducted by Prof. Ruby Shalom-Feuerstein and Dr. Shalini Dimri-Wagh from the Ruth and Bruce Rappaport Faculty of Medicine at Technion. Their work suggests that the body's ability to heal itself may be greater than scientists ever imagined — even in complex organisms like humans, where regrowing entire limbs was thought to be impossible.