Heterogeneity of the blood-brain barrier

ABSTRACT

The brain microvascular network is comprised of capillaries, arterioles and venules, all of which retain – although to a different extent – blood-brain barrier (BBB) properties. Capillaries constitute the largest and tightest microvasculature. In contrast, venules have a looser junctional arrangement, while arterioles have a lower expression of P-gp. Development and maintenance of the BBB depends on the interaction of cerebral endothelial cells with pericytes and astrocytes, which are all heterogeneous in different regions of the central nervous system. At the level of circumventricular organs microvessels are permeable, containing fenestrations and discontinuous tight junctions. In addition, the blood-spinal cord barrier – where the number of pericytes is lower and expression of junctional proteins is reduced – is also more permeable than the BBB. However, much less is known about the cellular, molecular and functional differences among other regions of the brain. This review summarizes our current knowledge on the heterogeneity of the brain microvasculature.

Keywords:

• astrocytes
• blood-brain barrier
• blood-spinal cord barrier
• cerebral endothelial cells
• circumventricular organs
• gray and white matter
• microvessel
• neurovascular unit
• pericytes
• regional differences

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Funding

The work of I.A.K. and I.W. is financed by the Hungarian Scientific Research Grant (OTKA K-100807, K-116158 and PD-100958). M.S. was financed by the strategic grant POSDRU/159/1.5/S/133391 within the project “Doctoral and post-doctoral programs of excellence for highly qualified human resources training for research in the field of Life sciences, Environment and Earth Science” co-financed by the European Social Fund within the Sectorial Operational Program Human Resources Development 2007 – 2013.