Biomedical engineers at Duke University have developed an injectable biomaterial that encourages the brain to repair itself after an ischemic stroke. Rather than replacing lost brain tissue, the experimental treatment transforms the cavity left behind by severe strokes into an environment that supports the body's own repair mechanisms. In preclinical experiments, the approach stimulated blood vessel formation, promoted neural remodeling and improved motor function in mice.
The findings suggest a new strategy for stroke recovery that focuses on rebuilding the damaged tissue environment rather than restoring blood flow alone. Although the results are promising, the researchers emphasize that the therapy remains at an early, preclinical stage and requires further testing before it can be evaluated in patients.
A supportive environment
Ischemic strokes occur when a blood clot blocks blood flow to part of the brain. While clot-dissolving drugs and mechanical thrombectomy can restore circulation and prevent further damage, they cannot regenerate brain tissue that has already been lost. Large strokes often leave behind permanent cavities where dead tissue has been cleared away, leaving rehabilitation as the primary option to help patients regain function.
The Duke research team sought to address this limitation by engineering a biomaterial capable of turning the damaged area into a regenerative environment. The treatment is based on microporous annealed particle scaffolds (MAPS), a network of hydrogel microparticles that forms a porous three-dimensional structure into which cells can migrate and rebuild tissue.
Rather than serving solely as structural support, the scaffold was designed to actively direct the repair process by interacting with the immune system. "Our goal is to engineer the injured space so that immune, vascular and neural repair processes can begin to work together," said senior author Tatiana Segura, Robert Plonsey Distinguished Professor of Biomedical Engineering at Duke University.
The brain's own repair mechanisms
To stimulate regeneration, the researchers incorporated extracellular vesicles (EVs) derived from astrocytes, the star-shaped brain cells that play an important role in maintaining healthy brain function and responding to injury. These microscopic vesicles carry proteins, lipids and genetic material that enable cells to communicate. Instead of injecting the vesicles directly, the team chemically attached them to the hydrogel particles. This localized the biological signals within the scaffold, allowing incoming immune cells to interact with them over an extended period.
The researchers tested different signaling molecules and found that a combination of IL-4 and C1q most effectively attracted immune cells associated with tissue repair, including macrophages and a surprisingly persistent population of neutrophils. Neutrophils are generally regarded as early inflammatory cells that contribute to tissue damage after stroke. However, the study suggests that under the right conditions and at a later stage of recovery, these cells may instead promote regeneration.
When the researchers experimentally removed the neutrophil-rich cell population, both blood vessel formation and scaffold remodeling were significantly reduced, indicating that these immune cells played a central role in the repair process.
Blood vessels and functional recovery
The immune response triggered by the scaffold coincided with extensive formation of new blood vessels throughout the damaged brain cavity. The researchers also observed increased numbers of axonal fibers, essential structures that enable neurons to communicate. These biological changes were accompanied by functional improvements. Mice treated with the optimized scaffold performed significantly better on a grid-walking test measuring forelimb coordination. After eight weeks, their performance was statistically comparable to that of healthy control animals, with improvements maintained throughout the study.
Importantly, administering extracellular vesicles without the scaffold failed to produce similar vascular repair, demonstrating that the biomaterial itself played an essential role by providing both structural support and localized biological signaling.
Proof of concept
The study represents an important proof of concept but remains limited to animal models. The biomaterial was injected directly into the stroke cavity in mice, and additional studies are needed to assess safety, better understand the contribution of different immune-cell populations and evaluate the therapy in larger, clinically representative stroke models.
The researchers are already working on the next phase by replacing rat-derived astrocyte vesicles with extracellular vesicles generated from human induced pluripotent stem cell-derived astrocytes. This approach could provide a more scalable and clinically relevant source of therapeutic signals while offering greater control over the biological cues delivered by the scaffold.
Rather than attempting to recreate lost brain tissue, the researchers envision creating conditions in which the body's own cells can re-enter the damaged area, communicate with one another and rebuild functional, vascularized tissue. If future studies confirm these findings, the strategy could open a new avenue for regenerative therapies aimed at improving recovery after severe ischemic stroke.
Stroke research
Last year, Australian researchers developed ultra-precise 3D-printed blood vessels that replicate both the structure and blood flow dynamics of human arteries, providing a patient-specific platform to study how stroke-causing blood clots form. The technology uses CT scans to create microscopic replicas of healthy and diseased carotid arteries in just two hours, significantly faster than conventional methods. The models preserve subtle anatomical features and enable researchers to observe platelet behaviour under realistic flow conditions.
The study found that high stress on vessel walls, associated with hypertension and atherosclerosis, increased platelet activity seven- to tenfold, an early step in clot formation. According to the researchers, the platform could improve personalized stroke risk assessment, support treatment development, and reduce reliance on animal experiments by enabling patient-specific testing in the laboratory.
References
Cell Biomaterials (research)
