From Dr. Putnam to Astrocytes--MS as a Vascular Disease

June 22, 2012 at 12:04pm

For those who haven't had a chance to read about the history of the beginnings of the MS Society and the founding neurologist, Dr. Tracy J Putnam---here's a bit of background on the vascular history of MS.
http://ccsviinms.blogspot.com/2012/06/dr.html

The very latest research into multiple sclerosis is discovering what Dr. Putnam hypothesized. MS is created by a response from the vascular system to injury. 

New research, published this month, continues Putnam's thesis, at the cellular level.

Something is signaling the vascular cells in the brain.

Here's how it works.

Astrocytes are beautiful, star-shaped cells that live in the central nervous system. ( I love the fact that our smallest cells look like the largest bodies in our solar system.  There's wonderful symmetry in creation.)

Astrocytes are the most abundant cell in the human brain.  One of the most important things astrocytes do is support the endothelial cells in our brain, and maintain the very important blood brain barrier. The blood brain barrier should have tight junctions, that don't allow blood particles into brain or spinal tissue.  (For those new to the idea of the endothelium, please check out the Endothelial Health program I made for Jeff.  It will explain how MS and our blood supply are connected.)

http://www.ccsvi.org/index.php/helping-myself/endothelial-health

Researchers have recently noted that when the brain is subject to hypoxia, or low levels of oxygen, the blood brain barrier becomes open, or "permeable."  This allows infiltration of blood cells and the immune system, which create damage to the brain.  Please notice that if the blood brain barrier was not open, T and B cells would not have entry.  The immune system isn't just going into the brain, uninvited and without cause.  The gate is wide open.

Blood brain barrier (BBB) permeability is an early and prominent feature of inflammatory CNS conditions, including MS (13), viral encephalitis (14), and traumatic and hypoxic/ischemic injury (15). BBB disruption correlates with neurologic exacerbation, and MS patients with contrast-enhancing plaques are more likely to have irreversible pathology (13, 16). BBB breakdown leads to edema, metabolic imbalance, excitotoxicity, and ingress of factors that potentiate inflammation and inhibit repair (17–20) and facilitates infiltration of T and B lymphocytes, macrophages, and neutrophils (21). In diseases such as MS, current options to restrict relapse severity are limited, and patients may benefit from more selective agents (22).

What is going on?  What signals the astrocytes to open the gate?  Researchers are looking specifically at VEGF--vascular endothelial growth factor.

Studies have identified astrocytes as regulators of BBB induction and maintenance (9–11) and have implicated astrogliosis, particularly induced by IL-1, as a driver of both BBB breakdown and repair (10, 12, 48). The mediators producing the effects of reactive astrocytes are incompletely characterized, and our data revealed VEGF-A as an important astrocyte-derived inducer of BBB disruption and pathology in vivo. Although VEGF-A–induced vascular permeability has previously been implicated in pathogenesis of disorders, including myocardial infarction, CNS hypoxia/reperfusion injury, and tumor growth and metastasis (49), and we and others have previously speculated on its role in BBB breakdown (12, 26), this study is the first to our knowledge to show the significance of astrocyte-derived VEGF-A in lesion pathogenesis and generation of clinical deficit in models of CNS inflammatory disease.

http://www.jci.org/articles/view/60842

This is the first study that has noted the importance of astrocyte derived VEGF in the formation of lesions and brain damage in a model of MS.

Please note the other diseases that have VEGF created "vascular permeability"--hypoxia and myocardial infarction--are vascular diseases.  VEGF-a is activated in situations where there is low oxygen, and the organ begins to suffer the effects of low O2.

So, what is VEGF and why does it matter in MS?  

Vascular endothelial growth factor (VEGF) is a chemical signal produced by cells that stimulates the growth of new blood vessels, called "angiogenesis."  This is part of a system which restores the oxygen supply to tissues when blood circulation is inadequate.

VEGF's normal function is to create new blood vessels during embryonic development, new blood vessels after injury, and new vessels (collateral circulation) to bypass blocked vessels.

Here is a rather pejorative look at the vascular connection, written in a condescending tone by a group of German Neurologists-- 

Vascular pathology in multiple sclerosis: mind boosting or myth busting?

The idea of MS being a vascular disease is not new. In the 1930s T.J. Putnam proposed venous obstruction as the primary alteration in MS [7]. Given the venotopic localization of MS plaques, this hypothesis has been discussed on and off ever since. In 2007 an Italian group headed by P. Zamboni added new fuel to the fire by demonstrating that venous blood flow alterations can be found at a high frequency in MS patients [5]. 

While the concept of CCSVI has gained much attention in the field of MS research and in particular among MS patients, there is increasing evidence that the relation of venous changes to the pathophysiology of MS may not be as simple as initially described. Most importantly, new MR imaging techniques add to the notion of vascular changes in MS, yet again raise doubts whether these alterations are cause or rather consequence of the disease process.

(At the end of the article, the authors state they have nothing to disclose, yet all of them have participated in many MS drug trials. Drugs which are based on the EAE immune model of MS-  Dr. Linker has received personal compensation for activities with Bayer Health Care, BiogenIdec, Merck Serono, Novartis and TEVA Pharma. Dr. Linker has received research support from BiogenIdec, Novartis and TEVA Pharma.)

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3156723/?tool=pubmed

Why is it only neurologists who believe some "mystery mechanism" disease process is behind VEGF activation, blood brain barrier disruption and inflammation---when we have other models of vascular disease in vivo, such as stroke, which illustrate how hypoxic injury creates this scenario? 

If MS specialists want to continue to pretend there is no vascular involvement in MS, and that MS is a disease of a mysterious and crazed immune system,  they can keep saying it-- and creating, testing and selling the drugs.  But the truth is, all of the research continues to point to the importance of the endothelium and the vascular response of the body to injury of the brain.  

What's causing the injury?  Slowed flow through the brain, hypoperfusion, low O2 and glucose levels from collateral venous return?   Makes sense to me.   More to come.

Joan