Perivascular structures in corrosion casts of the human central nervous system: A confocal laser and scanning electron microscope study

Abstract

Scanning electron microscopy (SEM) of microvascular corrosion casts revealed perivascular structures that resembled smooth muscle and pericyte cells. Although these structures have been studied in widely different experimental contexts, their origin, function, and distribution pattern in different tissues are not understood. Microvascular corrosion casts from 15 fresh human brains and 20 lumbar spinal cords were studied by SEM. In five cerebral hemispheres a fluorescent resin was injected in order to study the vascular bed by confocal laser scanning microscopy (CLSM). Microvascular casts showed two perivascular structures on their surfaces: plastic strips, which formed a muff around arteriolar vessels, and pericyte-like structures that were present around the capillary network. Their morphological characteristics and distribution were similar to those of smooth muscle cells and pericytes, respectively. The SEM study showed that these structures were not tightly joined to the cast surface, but were connected to the vascular cast by narrow plastic connections. The CLSM showed that the resin invaded the subendothelial space, thus giving rise to these structures. Perivascular structures associated with arteriolar and capillary vessels appear to represent smooth muscle cells and pericytes. They are formed by the passage of the resin to the subendothelial space, probably through weak endothelial cell junctions. The effusion of resin into the subendothelial space may represent evidence for the structural basis of myocyte and pericyte cell control. Chemical communication by substances released locally or transported to these cells through these junctions may regulate their functions, allowing them to regulate blood flow.

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network. Part II: Flow variations induced by global or localized modifications of arteriolar diameters

“…One of the main components involved in brain blood flow control and regulation is the smooth muscle cells associated to resistance arterioles in the pial (Girouard and Iadecola, 2006) and intra-cortical arteries (Rodriguez-Baeza et al, 1998;Girouard and Iadecola, 2006). In the human brain, the detailed electron microscopy study of corrosion casts performed by Rodriguez-Baeza et al (1998) suggests the existence of a lower bound value for the diameter of arterioles that can exhibit active vasodilation.…”

“…In the human brain, the detailed electron microscopy study of corrosion casts performed by Rodriguez-Baeza et al (1998) suggests the existence of a lower bound value for the diameter of arterioles that can exhibit active vasodilation. In order to investigate the effect of the existence of a minimal diameter in arteries exhibiting active vasodilation, two values of d vaso have been chosen in the present study, the first, 9.9 μm, corresponding to the diameter threshold for capillary vessels and the second, 14.9 μm.…”

Coupling between neuronal activity and microcirculation: Implications for functional brain imaging

“…Nevertheless, functional recruitment of red blood cells to the capillary bed has been observed in scanning laser-Doppler flowmetry experiments in the cerebellar cortex of rats upon stimulation of climbing and parallel fibers (Akgoren and Lauritzen, 1999), and functional capillary recruitment has been deduced indirectly from comparing the ratio between CBF and cerebral metabolic rate for glucose (CMRGlu) upon stimulation and at rest in human parietal cortex (Kuwabara et al, 1992). Moreover, accumulating experimental evidence from microscopic investigations shows that capillaries are indeed endowed with the "machinery" needed to control their diameter (Rodriguez-Baeza et al, 1998;Harrison et al, 2002) and that this machinery responds to stimulation (Peppiatt et al, 2006, in retina).…”

New Applications of Nanotechnology for Neuroimaging

“…[45][46][47] Recently, noninvasive imaging of neural progenitor cells during angiogenesis was demonstrated in a bilateral carotid artery occlusion murine model by using gene transcript-targeted MR imaging contrast agents. In this ischemic brain injury model, SPIO nanoparticles, modified with micro DNA targeting actin and nestin messenger ribonucleic acid (the latter uniquely expressed by pericytes), were administered to mice after bilateral carotid artery occlusion to image vessel formation by the detection of cerebral pericytes.…”