Factors Released from Endothelial Cells Exposed to Flow Impact Adhesion, Proliferation, and Fate Choice in the Adult Neural Stem Cell Lineage

Abstract

The microvasculature within the neural stem cell (NSC) niche promotes self-renewal and regulates lineage progression. Previous work identified endothelial-produced soluble factors as key regulators of neural progenitor cell (NPC) fate and proliferation; however, endothelial cells (ECs) are sensitive to local hemodynamics, and the effect of this key physiological process has not been defined. In this study, we evaluated adult mouse NPC response to soluble factors isolated from static or dynamic (flow) EC cultures. Endothelial factors generated under dynamic conditions significantly increased neuronal differentiation, while those released under static conditions stimulated oligodendrocyte differentiation. Flow increases EC release of neurogenic factors and of heparin sulfate glycosaminoglycans that increase their bioactivity, likely underlying the enhanced neuronal differentiation. Additionally, endothelial factors, especially from static conditions, promoted adherent growth. Together, our data suggest that blood flow may impact proliferation, adhesion, and the neuron-glial fate choice of adult NPCs, with implications for diseases and aging that reduce flow.

Bioengineering the neurovascular niche to study the interaction of neural stem cells and endothelial cells

“…Under flow conditions, BECs demonstrated enhanced secretion of EGF and bFGF, in addition to HSPGs which likely increased growth factor bioactivity similar to the way that HSPG-rich fractones have in vivo. 126 These data suggest that the release of BEC-derived soluble factors is flow-dependent and emphasize the capacity of in vitro models to replicate physiological conditions.…”

“… 77 Notwithstanding 2D cell culture constraints, Dumont and colleagues demonstrated the influence of flow on endothelial cell-derived soluble factors and NPC fate. 126 Briefly, a cone-plate viscometer exposed bEnd.3 cells to a shear stress of 0 (static) or 10 dynes/cm 2 (flow) and adult mouse NPCs were cultured with conditioned medium from both regimes. Conditioned medium from static and flow conditions promoted oligodendrocyte and neuron differentiation, respectively.…”

Endothelial Cells Exposed to Fluid Shear Stress Support Diffusion Based Maturation of Adult Neural Progenitor Cells

“…We previously demonstrated that ECs stimulated by fluid flow alter cytokine production to support heterogeneous SVZ populations. 16 Similarly, in this work we evaluate SVZ cell heterogeneity local to the ECs, but find less heterogeneity within NPC populations farther from EC monolayers or within static co-cultures, emphasizing the importance of a model that considers ECs exposed to fluid shear stress as well as spatiotemporal signaling between the ECs and NPCs that mimics the SVZ cytoarchitecture.…”

“…27,31,52,59,64 We have previously show the mBend EC cell line can produce glycosaminoglycans, a primary constituent of proteoglycans, and that production is increased by the culturing of these cells under dynamic fluid flow. 16 In this work we propose a co-culture model, wherein dynamically cultured ECs provide growth factors, as well as stabilizing proteoglycans to recapitulate complex soluble factor gradients to NSCs in vitro.…”

“…This is supported with previous research in which conditioned medium isolated from ECs cultured under shear stress resulted in profound differences in NPC adhesion, proliferation, survival, and differentiation compared to static EC-conditioned medium. 16 In this work, a novel niche model was developed that concurrently cultures the ECs under fluid shear stress (dynamic culture), while NPCs reside in endothelial-conditioned microenvironment without fluid flow. This was achieved with a modified cone and plate viscometer that applied a shear stress of 10 dynes cm À2 to EC monolayers cultured on transwell membranes while the NPCs were cultured below at a distance of 10 or 1000 lm from the ECs.…”