#pericytes

[bpod-bpod]

Thoughtful Neighbours

Two very different tissues meet at the blood-brain barrier, where our circulatory system delivers usable energy to hungry neurons while preventing harmful pathogens from accidentally leaking into the brain. This delicate process requires regular communication, and is still a little mysterious. In this slice through a developing mouse brain, endothelial cells lining vessels (green) are surrounded by pericytes (red), which contract to control traffic through the barrier. Meanwhile, in neighbouring neurons on the other side, researchers found molecules that help switch important genes on or off by controlling access to the DNA – a process known as epigenetics – can cause drastic changes in the neuron’s metabolism. Reacting to these chemical changes, pericytes relax the blood-brain barrier, potentially increasing the risk of infection. As epigenetic controls change as we age, they may hold the clues to the role of blood-brain communication in Alzheimer's disease and vascular dementia.

Written by John Ankers

Image by Bilal N. Sheikh, Max Planck Institute of Immunobiology and Epigenetics

Max Planck Institute of Immunobiology and Epigenetics, Freiburg im Breisgau, Germany

Image copyright held by the original authors

Research published in Nature Cell Biology, June 2020

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[neurosciencenews]

Certain cells secrete a substance in the brain that protects neurons

Vascular cell loss results in neuron loss, researchers report. However, pericytes secrete a substance that helps protect neurons, even when vascular cell degeneration begins to occur.

[neurosciencenews]

Half of All Dementias Start with Damaged 'Gatekeeper' Cells

USC research sheds new light on how a breakdown in the brain’s vascular system predates the accumulation of toxic plaques and tangles in the brain that bring about Alzheimer’s disease. The research suggests an earlier target for preventing dementia and Alzheimer’s.

The research is in Nature Medicine. (full access paywall)

[neurosciencenews]

How the Brain Responds to Vascular Injury

Pericytes, a little-understood type of cell on the brain's blood vessels, grow into the empty space left when neighboring pericytes die, report researchers at the Medical University of South Carolina.

The research is in Cell Reports. (full open access)

[bookpiofficial]

Diabetic Retinopathy– An Overview | Book Publisher International

Diabetic retinopathy is the leading cause of blindness world over. Neurovascular degeneration of the retina is considered presently as the cause as against the vascular changes which are believed to be causative previously. In fact the neuronal changes are shown to ante-date the vascular changes. There is complex interaction of many cells like pericytes, mullers cells, astrocytes, vascular endothelial cells as well as factors like advanced glycation products, Oxidative and metabolic stress, inflammatory cytokines, leukotrienes, various growth factors and glycoproteins etc. in the pathogenesis of DR. Various biochemical pathways like Polyol pathway, glucosamine pathway, AGE pathway and PKC pathways interacting with one another is also recognised as having a role in the pathogenesis of DR. But the common link responsible for all these factors involvement linking to DM2 is still not clear. The mechanism explaining Benfotiamine, a thiamine analogue found to be useful in treating DR , though attractive in integrating the various biochemical pathways cited above, is not comprehensive. The concept of reactive oxygen species (ROS) is a better alternative explanations linking up all pathogenic factors concerned to chronic hyperglycaemia of DzM2. But antioxidants proved futile in treating DR. It may be useful to remember that extensive ROS production in DM2 is consequent to shift of energy metabolism from glycolysis to B-oxidation of fats. Unless this is reversed, ROS production continues. The Diabetes Control and Complications Trial (DCCT) and UKPDS are the two landmark clinical trials that clearly showed the relationship between chronic hyperglycaemia and genesis of DR. Progression in T1DM and T2DM patients, respectively. Randomized controlled trials have shown that early treatment of DM2 can reduce an individual’s risk of severe visual loss by 57%. Intensive glycaemic control appeared long lasting because of the metabolic memory, also known as ‘legacy effect’. A term which explains the beneficial effects of immediate intensive treatment of hyperglycaemia with a sustained benefit with respect to the outcomes for many years, regardless of glycaemia in the later course of diabetes. Hence the current emphasis is prevention of DR with strict glycaemic control in DM2 ab initio.

Author(s) Details

A. S. V. Prasad

Department of Internal Medicine, GITAM Dental College, Rishikonda, Visakhapatnam, Andhra Pradesh, India.

Read full article: http://bp.bookpi.org/index.php/bpi/catalog/view/32/100/200-1

View Volume: https://doi.org/10.9734/bpi/mono/978-81-940613-1-1

[currentsinbiology]

What controls blood flow in the brain?

In a paper published on June 25 in Neuron, Yale University scientists present the strongest evidence yet that smooth muscle cells surrounding blood vessels in the brain are the only cells capable of contracting to control blood vessel diameter and thus regulate blood flow. This basic anatomical understanding may also have important implications for phenomena observed in stroke and migraines.

Smooth muscle cells line the thicker blood vessels in the brain, while the branching capillaries are covered by a mysterious cell type called pericytes. Pericytes are not muscle cells or neurons, but they are found in large numbers in the brain and are thought to play a role in blood vessel formation. Previous studies have suggested that pericytes could contract to regulate blood flow in the smaller blood vessels, but the new Neuron paper contradicts this theory.

'We found that when neurons fire more actively (either during normal brain activity or events such as migraines) there is a response in small blood vessels that are covered by smooth muscle cells, but not those that are covered by pericytes,' says senior study author Jaime Grutzendler, director of Yale School of Medicine's Center for Experimental Neuroimaging.

Robert A. Hill, Lei Tong, Peng Yuan, Sasidhar Murikinati, Shobhana Gupta, Jaime Grutzendler. Regional Blood Flow in the Normal and Ischemic Brain Is Controlled by Arteriolar Smooth Muscle Cell Contractility and Not by Capillary Pericytes. Neuron, 2015; DOI: 10.1016/j.neuron.2015.06.001

The major arteries of the brain. (A) Ventral view (compare with Figure 1.13B). The enlargement of the boxed area shows the circle of Willis. Lateral (B) and (C) midsagittal views showing anterior, middle, and posterior cerebral arteries. (D) Idealized frontal section showing course of middle cerebral artery. From: The Blood Supply of the Brain and Spinal Cord