Abstract: The present invention is a composition, and a method for making and administering, a pharmaceutical in unit dosage form in which mitochondria-enriched extracellular vesicles are delivered, “as is” or with an optional suitable carrier, after increasing the mitochondria content of the vesicles by generating the vesicles from a human brain endothelial cell line in the presence of one or more suitable promoting agents. Such mitochondria-enriched vesicles are effective to treat tissues needing amelioration of mitochondrial dysfunction or boosting of mitochondrial function. The EVs intrinsically are able to cross the blood-brain barrier and thus are particularly well suited for treating compromised tissues of the brain in situ. as well as other tissues under stress and in need of treatment not limited to neurologic tissues, and are typically administered parenterally.