As we get older, our skin naturally becomes thinner, slower to heal, and less able to stay healthy.
Scientists have long tried to understand why this happens and whether it can be reversed.
Now, researchers from the New York University School of Medicine have made a breakthrough that could point to a new way to restore aging skin—at least in mice.
They discovered that certain immune cells in the skin, called macrophages, decline with age, and that increasing them can help old skin repair itself more effectively.
Macrophages are tiny immune cells that protect the body by eating up damaged cells and germs. They also help repair tissues when they are injured. These cells live in nearly every organ and body tissue, forming local “niches” where they perform important repair and maintenance work.
In the skin, macrophages are found in the layers known as the epidermis and dermis. The upper part of the dermis contains small blood vessels, called capillaries, which deliver oxygen and nutrients to the skin.
Over time, both the number of capillaries and the macrophages that support them start to decrease. When these capillaries weaken or disappear, the skin doesn’t get enough nutrients or blood flow.
This can lead to slower healing, fragile skin, and problems like chronic wounds. Scientists have also found similar age-related damage in other organs, such as the brain, where reduced blood flow can contribute to diseases like Alzheimer’s.
In this new study, published in the journal Nature, researchers wanted to understand exactly how these macrophages behave in aging skin and whether they could be restored. The study was titled “Niche-specific dermal macrophage loss promotes skin capillary ageing.”
The research team used advanced imaging techniques, including a special method called two-photon microscopy, to watch how these immune cells moved and worked in the skin of live mice.
They studied mice from 1 month to 24 months old, which allowed them to compare young and old animals. In addition, the team looked at skin samples from humans—five younger people under 40 and six older people over 75—to see if the same changes happen in human skin.
They found that in both mice and humans, the number of capillary-associated macrophages—called CAMs—dropped with age. This decline made the capillaries weaker and reduced blood flow in the skin. Essentially, as macrophages disappeared, parts of the skin lost their ability to repair and stay healthy.
To test whether these cells could be restored, the scientists gave some of the older mice a growth factor called CSF1–Fc. This compound helps boost the renewal of macrophages. The treatment was given by injection into the skin for four days. After that, the researchers examined the treated skin under a microscope.
The results were striking. The older mice that received CSF1–Fc had more macrophages, stronger blood flow, and faster repair of damaged capillaries.
When the researchers intentionally created tiny blockages in the skin’s capillaries, the treated mice recovered blood flow much more easily than those that did not get the treatment. The capillaries also showed fewer clogs overall.
These results suggest that renewing local macrophages can restore part of the skin’s repair system, at least in mice.
However, the study also showed that this rejuvenation was limited to small blood vessels—it did not completely reverse all signs of aging or restore younger-looking skin. The team did not test the treatment on humans, so it is not yet clear whether the same results would happen in people.
Still, the findings offer an exciting clue about how aging might be slowed down. The study suggests that one reason tissues age is because they lose the ability to renew macrophages in their local areas, creating “gaps” in the skin’s defense and repair systems. By filling those gaps, it may be possible to protect or even restore tissue health.
In conclusion, this research shows that a small but important group of immune cells plays a key role in maintaining healthy skin. By boosting these cells, scientists were able to restore blood flow and repair capacity in old mouse skin.
More studies are needed to confirm if this approach can be safely used in humans, but the idea of reversing skin aging by renewing the body’s natural repair cells could open a new chapter in regenerative medicine.
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The study is published in Nature.
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