Revealed in a paper from the journal Cell Biomaterials this past July, researchers at Duke University have had their first success with a new treatment approach for stroke patients. After a stroke, there is a cavity left behind where cells have died. Existing treatments for stroke patients can restore blood flow to the affected area and attempt to retrain surviving neural pathways to restore normal day-to-day function, but the dead cells cannot be revived or replaced. The key innovation of this approach is that it attempts to create what the researchers call a “regenerative immune niche” inside that cavity.
Essentially, they created an injectable material that fills the cavity and facilitates healing and regrowth of neurons and blood vessels. This material included both a structural base upon which brain cells can be rebuilt inside the cavity and particles that would stimulate the immune system to do the rebuilding. The structural base is provided by particles called MAPS, which are an injectable form of hydrogel microparticles that form a porous structure for new neurons to fill. This creates a kind of “scaffolding” inside the brain. The immune system stimulation is done via extracellular vesicles (EVs), which act like little delivery drivers in the brain, carrying proteins, lipids, and information between cells. The EVs they used were derived from cells called astrocytes; these brain cells are normally part of the brain’s injury response mechanism.
The new treatment method was tested and evaluated by injecting the particle scaffold into mice five days after a stroke. This demonstrates the key advantage of the new treatment, as it is well after the brief time window for a thrombectomy, a currently available stroke treatment involving removal of the blood clot. Although the time window is expanding with new studies being done, a thrombectomy can still only be performed within 6 to 16 hours of the stroke’s onset.
The results of the test on mice were positive in multiple ways: new blood vessels were formed inside the cavity where the injection was made, and the mice showed improvement on a grid-walking test that measured forelimb placement error. This means that there were not only measurable biological changes in the mice’s brains, but also significant progress made in movement. Importantly, these changes persisted throughout the study, not regressing over time.
The treatment is still pre-clinical, having been tested only on mice using EVs from rat astrocyte cells. However, the positive results suggest that the mechanism could work in human brains as well, and next steps will involve safety assessments and attempts to produce similar results in models that are closer in size and structure to the human brain.
