Could Switching Off One Cell Signal Help Keep Our Bodies Young?

Scientists have found a new way that the body might be kept young — or allowed to grow old. A study published in the journal Science looked at special immune cells that live inside our organs. Researchers found that turning off one chemical signal in these cells helped older mice look and act much younger. The study showed improvements in the brain, heart, muscles, liver, and gut all at once.

Our bodies are full of immune cells that work like tiny janitors. Some of these cells, called tissue-resident macrophages, or TRMs, live inside our organs and clean up old or damaged cells. Think of them as a cleanup crew that is always on duty. When these janitors do their job well, our organs stay healthy. When they stop working properly, harmful waste builds up.

As we age, our bodies can build up low-level inflammation — a kind of constant, slow-burning fire inside our tissues. Scientists call this inflammaging, a mix of the words inflammation and aging. This ongoing inflammation damages organs over time and makes us feel and function older than we should. The new study found that TRMs play a big role in whether this fire starts or stays under control.

The key player in the study is a protein called EP2, which sits on the surface of TRMs like a switch. When EP2 is turned on, the TRMs do not clean up old, harmful cells as well as they should. The scientists — led by researcher Tan and colleagues — tested what happened when they turned this EP2 switch off in mice. The results were striking across many different organs.

The team used two groups of older mice — one with EP2 turned off in their TRMs, and one with EP2 left on as normal. Mice without EP2 in their TRMs had far less inflammation in their livers, lungs, hearts, and brains. Their bodies looked more like those of young mice. The mice with EP2 still switched on showed the usual signs of aging, like organ damage and high inflammation.

When the researchers looked more closely, they found a specific problem in the aged mice with EP2 still on. Their TRMs were failing to clear out old, worn-out immune cells called senescent neutrophils. Neutrophils are a type of white blood cell that normally fights infection, but old ones can become harmful if they stick around too long. In aging livers, these old neutrophils were piling up and causing damage.

Removing the EP2 signal fixed this cleanup problem. The TRMs became better at finding and eating the old neutrophils. This cleared away a source of constant inflammation. As a result, the organs of older mice with EP2 turned off worked more like those of younger mice.

The benefits showed up in many parts of the body at the same time. Mice without EP2 in their TRMs had better memory and learning. They also had less body fat, more muscle strength, and healthier hearts. Their gut linings were stronger, and their livers showed less damage. It was as if the clock had been turned back in many organs at once.

The scientists also tested a drug that blocks EP2, instead of removing the gene. This drug had similar effects and brought the number of old, harmful neutrophils back down to youthful levels. This shows that a medicine, not just genetic changes, could one day be used to produce similar results. That is an exciting step toward treatments that could help people, not just lab mice.

The researchers also looked at human data and found that older and sicker human livers and hearts had fewer TRMs and more harmful neutrophils — just like in the older mice. This suggests the same problem may happen in people as they age. It also points to the liver as a key place where the body normally cleans up old, dangerous immune cells. If scientists can develop safe EP2-blocking drugs for humans, they may one day help people age in a much healthier way.