Image of blood cells

Small vesicles secreted by cells help facilitate growth and development of blood vessels and neurons in the brain following a stroke, according to a new study presented at the American Stroke Association’s International Stroke Conference 2016.

Researchers from Detroit and China, suspected that tiny vesicles, or containers called exosomes — which are secreted from cells and play a role in communication from one cell to another — might facilitate the growth and development of blood vessels (angiogenesis) and of nerve cells, or neurons (neurogenesis).

To test their hypothesis, the research team isolated cells from the brains of both healthy rats and rats whose brains had been damaged by a blood vessel blockage. Two types of cells were isolated: cerebral endothelial cells (which line blood vessels in the brain) and neural progenitor cells (which can differentiate into other types of brain cells). Exosomes were harvested from those cells and tagged with fluorescent particles. The fluorescent particles helped researchers determine if cells successfully internalized the exosomes.

Researchers first studied exosomes from endothelial cells engulfed in neural progenitor cells. They found that in rats with brain damage from a stroke, neural cells containing exosomes from endothelial cells multiplied more rapidly — and differentiated more distinctly — than neural cells with comparable exosomes from healthy rats.

Findings were similar when the experiment was conducted in reverse, applying exosomes from neural progenitor cells to endothelial cells: The exosomes from rats with the damaged brains more actively promoted growth and development of blood vessels, compared to the exosomes from healthy rats. The results suggest that exosomes may be useful in enhancing brain recovery after stroke, researchers said.