Astrocyte-endothelial interactions

Abbott NJ, Ronnback L, Hansson E. Astrocyte-endothelial interactions at the blood-brain barrier. Nat Rev Neurosci 2006 7(l) 41-53. 

Abbott NJ (2002) Astrocyte endothelial interaction and blood brain barrier. Permeability. A Anat 200 629-638. 

Abbott NJ. Astrocyte-endothelial interactions and blood-brain barrier permeability. J Anat 2002 200 629-638. 

The neurovascular unit places stroke in the context of an integrative tissue response in which all cellular and matrix elements, not just neurons or blood vessels, are players in the evolution of tissue injury. For example, efficacy of the blood-brain barrier is critically dependent upon endothelial-astrocyte-matrix interactions [93]. Disruption of the neurovascular matrix, which includes basement membrane components such as type IV collagen, heparan sulfate proteoglycan, laminin, and... 

Integrins are adhesion molecules involved in cell-matrix interaction. Integrins are heterodimeric membrane glycoproteins formed by the combination of an a- and p-subunit with an intracellular and an extracellular domain [115]. In the brain, endothelial cells, astrocytes, and the basal membrane such as laminin and collagen contribute to form the... 

Figure 4.1. The vascular blood-brain barrier three levels of complexity. The upper panel illustrates the brain endothelial cell. This is the functional and anatomical site of both barrier function and of saturable and non-saturable mechanisms of passage. The major modifications allowing both barrier function and selective penetration of substances are indicated. The middle panel illustrates other ceU types and structures important in BBB function. Pericytes are embedded in a basement membrane and astrocytes form a net-like structure over the capillary bed. Both cell types are in paracellular communication with the brain endothelial cells. Pericytes and astrocytes to some extent oppose each others effects on BBB fnnctions. The lower panel illnstrates the neurovascnlar nnit, a concept, that emphasizes integration of peripheral, BBB, and central interactions.

Other examples for the successful employment of co-cultures are the interaction between muscle and nerve cells (Shahar et aL, 1985) and the co-cultivation of vascular endothelial and smooth-muscle cells using microcarrier techniques (Davies Kerr, 1982) co-cultivation of cerebellar granule cells, cerebral cortical neurons and cortical astrocytes on collagen-coated dextran beads (CytodexS) and the production and release of specific neurotransmitters and enzyme synthesis resembling in vivo interactions between neurons and astrocytes (Westergaard et aL, 1991). 

It is a functional unit composed of groups of neurons and their associated astrocytes, interacting with smooth muscle cells and endothelial cells on the microvessels (arterioles) responsible for their blood supply, and capable of regulating the local blood flow. Within this organization, further modular structures can be detected. 

Cells of the CNS directly interact with other cell types, notably the capillary endothelial cells that comprise the blood-brain barrier (BBB). Astrocytes are essential for the maintenance of BBB structural integrity ami permeability... 

Fig. 1.4 Schematic view of the neurovascular unit or module and some of its components. Circulating blood elements, endothelial cells, astrocytes, extracellular matrix, basal lamina, adjacent neurons, and pericytes. After ischemia, perturbations in neurovascular functional integrity initiate multiple cascades of injury. Upstream signals such as oxidative stress, together with neutrophil and/or platelet interactions with activated endothelium, upregulate MMPs, plasminogen activators, and other pro-...

FIGURE 14.16 Schematic view of the blood-brain barrier. Endothelial cells form a continuous layer covering the inner surface of blood microvessels. At the point of contacts with brain tissues, these endothelial cells interact with pericytes and astrocytes. Nerve ending with specific neurotransmitters can also be observed. The light junctions (TJ) that link endothelial cells act as a physical barrier that blocks the paraceUular route and forces the molecular traffic to take the transceUijlar pathway (double arrows). 

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