Pulsed Focal ultrasound as a non-invasive method to deliver exosomes in the brain/stroke

Exosomes, a component of extracellular vesicles are shown to carry important small RNAs, mRNAs, protein, and bioactive lipid from parent cells and are found in most biological fluids. Investigators have demonstrated the importance of mesenchymal stem cells (MSCs) derived exosomes in repairing stroke lesions. However, exosomes from endothelial progenitor cells (EPCs) have not been tested in any stroke model nor has there been an evaluation of whether these exosomes target/home to areas of pathology. Targeted delivery of IV administered exosomes has been a great challenge and a targeted delivery system is lacking to deliver naïve (unmodified) exosomes from EPCs to the site of interest. Pulsed focused ultrasound (pFUS) is being used for therapeutic and experimental purposes. There has not been any report showing the use of pulsed low-intensity pFUS to deliver exosomes to the site of interest in models of stroke.

In this proof of principle study, Augusta University researchers have shown different parameters of pFUS to deliver exosomes in the intact and stroke brain with or without IV administration of nanobubbles. The study results showed that administration of nanobubbles is detrimental to the brain structures (micro bleeding and white matter destruction) at peak negative pressure (PNP) of >0.25 MPa, despite enhanced delivery of IV administered exosomes. However, without nanobubbles, pFUS PNP = 1 to 2 MPa enhances the delivery of exosomes in the stroke area without altering the brain structures.

Albumin and DAPI immunofluorescence labeling of pFUS applied mice brain with 0.25MPa + NB to left hemisphere, 0.5MPa to the right hemisphere

(A) 0.5MPa + NB to left hemisphere, 1MPa to the right hemisphere (B) 1MPa + NB to left hemisphere, 2MPa to the right hemisphere (C). Arrows indicate fluorescent-labeled albumin.