Cell-Free Extracellular Vesicles Derived from Human Bone Marrow Endothelial Progenitor Cells as Potential Therapeutics for Microvascular Endothelium Restoration in ALS

Repairing the damaged blood-CNS-barrier in amyotrophic lateral sclerosis (ALS) is necessary to prevent entry of detrimental blood-borne factors contributing to motor neuron dysfunction. Recently, we showed benefits of human bone marrow endothelial progenitor cell (hBM-EPC) transplantation into symptomatic ALS mice on barrier restoration by replacing damaged endothelial cells (ECs). Additionally, transplanted cells may endogenously repair ECs by secreting angiogenic factors as our subsequent in vitro study demonstrated. Based on these study results, hBM-EPCs may secrete extracellular vesicles, which may contain and transfer diverse vesicular biomolecules towards maintenance of EC functionality. The study aimed to characterize extracellular vesicles (EVs) derived from hBM-EPCs as potential cell-free therapeutics for endothelium repair in ALS. EVs were isolated from hBM-EPC media at different culture times and vesicle properties were evaluated. The protective effects of EVs on mouse brain endothelial cells (mBECs) exposed to ALS mouse plasma were investigated. Uptake and blockage of EVs from GFP-transfected hBM-EPCs in ECs were determined in vitro. Results showed that EVs isolated from hBM-EPCs as nanosized vesicles significantly reduced mBEC damage from the pathological environment and these EVs were taken up by cells. Blockage of β1 integrin on EVs prevented internalization of vesicles in mBECs. Together, these results provide evidence for potential of hBM-EPC-derived EVs as novel cell-free therapeutics for repair of endothelium in ALS. Although determining translational potential of hBM-EPC-derived EVs will require evaluation in vivo, this in vitro study represents a step towards an extracellular vesicle-based approach for repair of the damaged microvascular endothelium in ALS.