A photomicrograph showing new tissue growing in the stroke cavity in a mouse. Red tubes are blood vessels; green filaments are nerve fibers. Image: Courtesy of UCLA Health
A new stroke-healing gel created by UCLA researchers has helped to regrow neurons and blood vessels in mice with brains damaged by strokes. “We tested this in laboratory mice to determine if it would repair the brain and lead to recovery in a model of stroke,” says S. Thomas Carmichael, MD (FEL ’01), PhD, professor and chair of neurology at the David Geffen School of Medicine at UCLA. “The study indicated that new brain tissue can be regenerated in what was previously just an inactive brain scar after stroke.”
The results suggest that such an approach could be used to treat people who have had a stroke, says Tatiana Segura, PhD, who collaborated on the research when she was a professor of chemical and biomolecular engineering at UCLA. Dr. Segura now teaches at Duke University. The brain has a limited capacity for recovery after stroke. Unlike other organs such as the liver and skin, the brain does not regenerate new connections, blood vessels or tissue structures after it is damaged. Instead, dead brain tissue is absorbed, which leaves a cavity that is devoid of blood vessels, neurons or axons — the thin nerve fibers that project from neurons.
To see if healthy tissue surrounding the cavity could be coaxed into healing the injury caused by stroke, Dr. Segura engineered a hydrogel that, when injected into the cavity, thickens to create a scaffolding to support the growth of blood vessels and neurons. Medications infuse the gel to stimulate the growth of blood vessels and suppress inflammation; inflammation results in scars and impedes functional tissue from re-growing.
Sixteen weeks following treatment, brain tissue had regenerated within the stroke cavities. In addition, new neuronal connections were established — a result that had not been seen before. The ability of the mice to reach for food improved, a sign of better motor behavior, although the exact mechanism for the improvement wasn’t clear. “The new axons could actually be working,” Dr. Segura says. “Or the new tissue could be improving the performance of the surrounding, unharmed brain tissue.”
The body eventually absorbed the gel, leaving behind only new tissue. The researchers designed the study to explore recovery in acute stroke — the period immediately following a stroke, which in mice lasts five days and in humans two months. Next, Drs. Carmichael and Segura plan to investigate whether or not brain tissue can be regenerated in mice long after a stroke injury. More than 6 million Americans are living with long-term effects of stroke, which is known as chronic stroke.
“Dual-function Injectable Angiogenic Biomaterial for the Repair of Brain Tissue following Stroke,” Nature Materials, May 21, 2018
