Stimulation Of Blood Vessel Formation By Human Neural Stem/Progenitor Cells Is Mediated By Secreted Material

Human neural stem/progenitor cells (hNSPCs) have the potential to widen the current narrow treatment window for stroke as they improve functional recovery in rodent stroke models when transplanted weeks after stroke. One aspect of the hNSPC-induced functional recovery is increased angiogenesis and neovascularization in the peri-infarct region. Our lab created a human cell in vitro model of vessel formation by seeding hNSPCs and human endothelial progenitor cells (hEPCs) in a 3D scaffold composed of salmon fibrinogen, laminin, and hyaluronic acid that mimics brain tissue properties. Using our in vitro neurovascular model, we tested the hypothesis that hNSPC-secreted material plays a role in the stimulation of vessel formation. Our RNA-Seq data show that hNSPCs express high levels of secreted pro-angiogenic proteins, such as growth factors, matrix molecules, and cytokines, but hNSPCs might also impact vessel formation by secretion of extracellular vesicles or cell-contact mediated mechanisms. In order to determine the effect of hNSPC-secreted material on vessel formation, mCherry-labeled hEPCs were seeded in 3D scaffolds alone, with CellTracker Green-labeled hNSPCs, or with hNSPC-conditioned media containing hNSPC-secreted soluble factors and extracellular vesicles, such as exosomes. Vessel formation was quantified using AngioTool to determine total vessel length, number of branch points, and vessel percentage area. We found an increase in vessel formation in the presence of hNSPCs and hNSPC-conditioned media compared to hEPCs alone. In conclusion, material secreted by hNSPCs can recapitulate the increase in vessel formation induced by hNSPCs themselves. In future studies, we will determine whether hNSPC-derived exosomes are important for promoting vessel formation as they have therapeutic potential without the limitations of cell therapy.