A promising but still-experimental new treatment developed by researchers at Duke University is challenging the conventional approach to the recovery after a stroke — instead of attempting to directly replace the nerve cells that have been injured, scientists have created an injectable material that they believe can promote healing.

This work is still at the stage of being tested on animals, not yet ready for human stroke survivors, but the results could still represent an exciting potential avenue for future stroke recovery treatments.

Why repairing brain tissue after a stroke is so challenging

A stroke occurs when blood flow to a region of the brain is disrupted due to a blockage in an artery or due to a ruptured artery bleeding into the brain. Ischemic strokes occur when a clot blocks off an artery, preventing oxygenated blood from reaching downstream nerve cells.

Brain cells are extremely sensitive to a lack of oxygen, and significant damage can rapidly occur when oxygenated blood flow is disrupted — but even when emergency treatments like thrombolysis or thrombectomy can successfully restore blood flow, those interventions do not actually replace the damaged tissue.

In the case of severe strokes, damaged tissue may simply disappear, leaving behind the empty space that was previously filled by brain matter. Survivors can often recover some degree of function through rehabilitation, but actually refilling that empty space is one of the toughest problems in medicine.

According to the statistics cited by the World Health Organization in this report, there are around 11.9 million new strokes per year, and about 93.8 million people live today with the consequences of a stroke.

A scaffold that facilitates recovery

As detailed in this study published in Nature Biomedical Engineering , the Duke researchers have been experimenting with an injectable biomaterial composed of hydrogel microparticles, specifically MAPS, or Microporous Annealed Particle Scaffolds.

The material can be injected in liquid form, but once inside the body, the particles will bind together into a sponge-like structure.

This is not a regenerative substance in and of itself, but it creates a niche environment where cells can travel, bind to the scaffolding, and contribute to the repair process.

In addition, the researchers also added some extracellular vesicles, which they isolated from astrocytes, another type of brain cell.

The researchers attached some of these vesicles to the hydrogel particles — and they contained a number of different signaling molecules, including the protein interleukin 4 (IL-4) and complement component 1q (C1q). By delivering these specific signals, the researchers could cause desirable changes to occur.

The main discovery was that the localization of these signals made a significant difference.

When the researchers injected freely floating vesicles, without binding them to the hydrogel scaffolding, the signals were dispersed, and the desired effects were not seen. In contrast, when the researchers bound the vesicles to the scaffolding material, the resulting combination produced signals that were concentrated around the treatment site, and they guided the desired immune response to the area around the stroke cavity.

What did the researchers actually see in mice?

When the treatment was administered to mice, the researchers observed that new blood vessels and nerve fibers formed in and around the cavity, at the region of the stroke.

In addition, the researchers looked at motor function. Mice that had received the treatment showed equivalent motor performance to mice that had not suffered a stroke, beginning at around 8 weeks post-treatment.

Perhaps more interestingly, the treatment was administered more than 24 hours post-stroke. The timing is important, because most acute stroke treatments only remain effective if administered within a narrow time window following the onset of the stroke. If these results are confirmed, treatment that could be delivered later post-stroke would represent an enormous leap forward.

There is still a very long way to go before this treatment could be used in humans

It is important to remember that this is still a potentially promising but ultimately unproven treatment. These experiments were performed in mice — and the extracellular vesicles used in this study were obtained from rat astrocytes.

Basic science research like this takes time to progress from the research lab to the hospital setting. Before something like this could be considered for human use, researchers will need to ensure the safety and efficacy of this treatment in larger animals, and then in controlled human trials.

Notably, the researchers' suggested next step is to create the appropriate cell type using human pluripotent stem cells — and following that, additional studies would be needed in larger animal models before human trials might be considered.

There is still an enormous number of unanswered questions. Would this treatment be safe when administered to humans? Would the repaired tissue demonstrate normal functionality? Would it work for humans who have suffered different types and severity of strokes than the mice in these initial experiments? What long-term risks might it introduce?

A new direction in stroke recovery research, with very promising results

The value of this research lies in the fact that the researchers took a very different approach to the problem of post-stroke tissue repair. Instead of attempting to replace the tissue lost in a stroke, they created an environment where the repair might be able to occur.

As such, the results seen in mice are indeed promising, especially considering the observed vascular and neural regeneration, as well as the apparent functional recovery. At the same time, however, the results in mice have a very long way to go before they can translate into a meaningful change for human stroke survivors.

Right now, this is an exciting but ultimately unproven research direction — a potentially viable therapy, but not a treatment that is currently available to human stroke survivors.

If you or someone you care for is experiencing the signs or symptoms of a stroke, please get immediate emergency care — do not wait for an experimental treatment to arrive.

Sources and related information

As noted at the beginning of this article, this report has been published on ScienceDaily and La Tercera with additional commentary, along with information about the source article in Nature Biomedical Engineering .

The full ScienceDaily article, "Treatment developed to help the brain regenerate after a stroke" , is available at:

The full La Tercera article, "Científicos desarrollan un tratamiento que podría ayudar al cerebro a regenerarse después de un ACV" , is available at: