Abstract
BackgroundDuring angiogenesis in the developing central nervous system (CNS), endothelial cells (EC) detach from blood vessels growing on the brain surface, and migrate into the expanding brain parenchyma. Brain angiogenesis is regulated by growth factors and extracellular matrix (ECM) proteins secreted by cells of the developing CNS. In addition, recent evidence suggests that EC play an important role in establishing the neural stem cell (NSC) niche. Therefore, two-way communication between EC and neural cells is of fundamental importance in the developing CNS. To study the interactions between brain EC and neural cells of the developing CNS, a novel three-dimensional (3-D) murine co-culture system was developed. Fluorescent-labelled brain EC were seeded onto neurospheres; floating cellular aggregates that contain NSC/neural precursor cells (NPC) and smaller numbers of differentiated cells. Using this system, brain EC attachment, survival and migration into neurospheres was evaluated and the role of integrins in mediating the early adhesive events addressed.ResultsBrain EC attached, survived and migrated deep into neurospheres over a 5-day period. Neurospheres express the ECM proteins fibronectin and laminin, and brain EC adhesion to neurospheres was inhibited by RGD peptides and antibodies specific for the β1, but not the α6 integrin subunit.ConclusionA novel 3-D co-culture system for analysing the interactions between EC and neural cells of the developing CNS is presented. This system could be used to investigate the reciprocal influence of EC and NSC/NPC; to examine how NSC/NPC influence cerebral angiogenesis, and conversely, to examine how EC regulate the maintenance and differentiation of NSC/NPC. Using this system it is demonstrated that EC attachment to neurospheres is mediated by the fibronectin receptor, α5β1 integrin.
Highlights
During angiogenesis in the developing central nervous system (CNS), endothelial cells (EC) detach from blood vessels growing on the brain surface, and migrate into the expanding brain parenchyma
As an initial step in this study, primary cultures of mouse brain EC were seeded onto the surface of mouse neurospheres to determine whether EC would attach and migrate into neurospheres, as a means of recapitulating the EC ouside-in invasion of the CNS parenchyma that occurs during development
Integrins promote EC attachment to neurospheres This study has demonstrated that primary mouse brain EC attach, migrate and survive within mouse neurospheres, validating this system as a tool to investigate the molecular mechanisms mediating interactions between EC and neural stem cell (NSC)/neural precursor cells (NPC) within the developing CNS
Summary
During angiogenesis in the developing central nervous system (CNS), endothelial cells (EC) detach from blood vessels growing on the brain surface, and migrate into the expanding brain parenchyma. Fluorescent-labelled brain EC were seeded onto neurospheres; floating cellular aggregates that contain NSC/ neural precursor cells (NPC) and smaller numbers of differentiated cells. Using this system, brain EC attachment, survival and migration into neurospheres was evaluated and the role of integrins in mediating the early adhesive events addressed. Evidence suggests that the patterns of cerebral angiogenesis are closely matched to the requirements of the surrounding neural tissue This is well illustrated in the developing cerebral cortex in which emergence of the different neuronal layers is closely followed by the appearance of new blood vessels within each layer [2,4]. It has been shown that NSC promote vascular tube formation in brain EC in vitro, by a nitric oxide-mediated mechanism [8]
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