Extracellular vesicles of the blood-brain barrier

Abstract

Extracellular vesicles (ECV), like exosomes, gained recently a lot of attention as potentially playing a significant role in neurodegenerative diseases, particularly in Aβ pathology. While there are a lot of reports on ECV/exosomes derived from a variety of cell types, there is limited information on ECV/exosomes originated from brain microvascular endothelial cells forming the blood-brain barrier (BBB). In this review, we summarize the literature data on brain endothelial ECV/exosomes and present our own data on BBB-derived ECV and their possible involvement in the brain's Aβ pathology. We propose that ECV/exosome release from brain endothelial cells associated with Aβ affects different cells of the neurovascular unit and may be an important contributor to the Aβ deposition in the central nervous system.

Keywords: amyloid β; blood-brain barrier; brain endothelial cells; exosomes; extracellular vesicles.

Figure 1.

Extracellular vesicles from human brain microvascular endothelial cells (HBMEC). (A) Live fluorescence imaging of HBMEC transiently transfected with pT-CYTO-RFP and pT-CD63-GFP to visualize the brain endothelial cell (red) secreting green fluorescent CD63 positive extracellular vesicles (ECV). Scale bar: 2 μm. (B) HBMEC were transiently transfected with pT-CD63 GFP or pT-CD9 RFP. ECV were isolated from the cell culture media. Fluorescence microscopy images of isolated fluorescent ECV (CD63 GFP-green, upper panel; CD9 RFP-red, lower panel). Scale bar: 20 μm. (C) Differential interference contrast (DIC) image of isolated ECV. Scale bar: 2 μm.

Figure 2.

Dynamic light scattering analysis of isolated ECV from HBMEC. HBMEC-derived ECV were isolated from the cell culture media. (A) Size distribution indicates several peaks with the sizes of 68.41 nm, 609.1 nm and 5213 nm. (B) Volume distribution: 50.1% of the volume is for particles of ~60 nm, 2.4% for particles of ~5000 nm, and 47.4% for particles with an average diameter of ~600 nm.

Figure 3.

Exogenous Aβ (1-40) HiLyte in HBMEC-derived ECV. HBMEC were exposed to 100 nM Aβ (1-40) HiLyte for 48 h, followed by ECV isolation from cell culture media. Aβ (1-40) HiLyte (green fluorescence) in the isolated ECV was visualized by fluorescence microscopy. The images show the green fluorescent Aβ (1-40) HiLyte associated with ECV of different sizes. Scale bar: 20 μm.