For years, scientists studying Alzheimer’s disease have focused heavily on what happens to the brain’s nerve cells.

But researchers have now uncovered another piece of the puzzle — and it involves something many people might not immediately expect:

The brain’s blood vessels.

A team from the Icahn School of Medicine at Mount Sinai has identified a mechanism that helps explain how the APOE4 gene, the strongest genetic risk factor for Alzheimer’s disease, can damage blood vessels in the brain.

And researchers say the finding could point toward a completely different way of thinking about future Alzheimer’s treatments.

The APOE4 connection

Not everyone with APOE4 develops Alzheimer’s.

But scientists have long known that carrying the gene increases Alzheimer’s risk.

The new research helps explain why.

According to the researchers, APOE4 can cause cells called pericytes — cells that help support the brain’s tiny blood vessels — to change their behavior.

Instead of helping maintain healthy blood vessels, the cells can become more like scar-forming cells.

That can contribute to thickening of the blood vessels and buildup of abnormal proteins.

And that is where the discovery becomes especially interesting.

Scientists were able to reverse the damage — in mice

Researchers found that blocking a protein called TGF-beta reversed the blood-vessel damage in mice carrying APOE4.

The result does not mean scientists have found a treatment for Alzheimer’s in humans.

Human clinical trials would still be necessary to determine whether the approach is safe and effective.

But the experiment gives researchers another potential target to investigate.

Why blood vessels matter

Your brain needs an enormous amount of blood flow.

Blood vessels deliver oxygen and nutrients while helping remove waste.

So when those vessels become damaged, scientists believe that could affect the brain’s ability to function normally.

The new findings suggest that vascular damage may be more deeply connected to Alzheimer’s biology than researchers previously understood.

It’s not a cure — but it’s an important clue

This is the part worth remembering.

The research is promising, but it is not a cure, and people should not interpret the findings as proof that an Alzheimer’s treatment is around the corner.

The experiments involving reversal of the damage were performed in mice.

Still, scientific progress often starts with discoveries like this:

A previously unclear mechanism becomes understandable.

A new biological target is identified.

And researchers gain another direction to investigate.

Alzheimer’s research is looking at more than one piece of the puzzle

Alzheimer’s is an extremely complicated disease.

There isn’t necessarily going to be one single discovery that explains everything.

But each new piece of evidence can help researchers understand why the disease develops and how different parts of the brain may be affected.

This latest study adds an intriguing piece:

What happens to the brain’s blood vessels may be just as important as what happens to the brain cells themselves.

And researchers will now have to determine whether this discovery can eventually lead to something useful for people.

For millions of families affected by Alzheimer’s, even a new direction in research is something worth watching.

The next breakthrough may come from a part of the brain scientists once overlooked.