MicroRNA-126 is primarily expressed in endothelial cells (ECs), and is emerging as a key player in the pathogenesis of type two diabetes (T2DM) induced vascular damage. Stroke in T2DM increases vascular and white matter (WM) damage in the ischemic brain, and has a poor prognosis compared to non-DM stroke. In this study, we investigated the neurorestorative effects of exosomes derived from mouse brain ECs (EC-Exo) as a treatment of stroke in T2DM mice.
Methods: Adult male BKS.Cg-m+/+Leprdb/J (T2DM) and db/+ (non-DM) control mice (3-4 m) were subjected to right extraluminal permanent distal middle cerebral artery occlusion (dMCAo), and intravenous injection at 3 days after dMCAo with: 1) PBS; 2) Liposome mimic as vehicle control (3X1010); 3): EC-Exo (3x1010); 4) Knockdown of miR-126 in EC-Exo (miR-126-/-EC-Exo, 3X1010); 5) Knock-in miR-126 in EC-Exo (miR-126+/+EC-Exo, 3X1010). Mice were sacrificed at 28 days after dMCAo.
Results:1) T2DM-dMCAo mice exhibit significantly decreased blood serum, brain tissue and brain-EC miR-126 expression compared to non-DM-dMCAo mice. 2) EC-Exo contain higher levels of miR-126 than exosomes derived from other types of cells (smooth muscle cells, neurons, astrocytes and marrow stromal cells); 3) EC-Exo treatment significantly increases axonal outgrowth and increases capillary tube formation in vitro. Compared to PBS or liposome mimic treatment groups, EC-Exo treatment of stroke in T2DM-dMCAo mice: 4) is safe and does not appear to induce adverse side effects in physiological parameters and does not decrease lesion volume, but significantly improves neurological outcome and cognitive function after dMCAo; 5) significantly increases axon, myelin, vessel density and increases artery diameter in the ischemic boundary zone; 6) significantly increases perfused vessel density measured by FITC-dextran injection. 7) miR-126-/-EC-Exo treatment significantly decreases, but miR-126+/+EC-Exo increases miR-126 expression compared to EC-Exo control. 8) miR-126+/+EC-Exo treatment significantly improves functional outcomes when compared to miR-126-/-EC-Exo, or PBS control.
Conclusion: Treatment of stroke with EC-Exo increases miR-126 expression and promotes neurorestorative effects after stroke in T2DM mice.