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MS Society supported study reveals neuroprotective role of immune cell

  • MS Society Funded

Background:

Microglia are a type of immune cell that act as the primary form of defense in the central nervous system (CNS). Microglia act by killing viruses, bacteria, or other foreign cells, as well as by assisting with wound healing processes by collecting, or “scavenging,” cellular debris. Recent research has outlined another, less defined role for microglia during early brain development, wherein they assist in creating synaptic connections, structures that allow for nerve cells to communicate. Microglia thus play an essential role in communication in the postnatal brain, however the activity of microglia in the adult brain is not fully understood.

It has been observed that microglia are especially active when the brain suffers from acute injury or chronic diseases such as MS, but whether their presence is protective or detrimental to the CNS has been debated, as studies have found conflicting results. While most studies have focused on the destructive role of microglia, new evidence has demonstrated protective effects.

A study recently published in Nature Communications by MS Society Postdoctoral Fellowship recipient Dr. Zhihong Chen and colleagues investigated the role of microglia in the adult brain,  and proposed a potential mechanism through which microglia are able to maintain the health and survival of nerve cells.

The Study:

Dr. Chen and colleagues used an advanced technique called 3D electron microscopy to visualize how microglia behave in the presence of inflammation in the brains of mice. The inflammatory environment causes the microglia to be active, enabling researchers to identify how they influence nerve cell activity. They also blocked the activity of active microglia to see if that would reverse the effect. Finally, they performed sophisticated cell experiments to better understand how microglia may be neuroprotective.

Results:

The researchers demonstrated that when microglia are activated they undergo an action known as “synaptic stripping.” This process involves removing a blockade which stops the neurons from functionally normally. This process enables microglia to increase communication between nerve cells, allowing the body to perform functions such as walking, seeing and speaking.  Through synaptic stripping, activated microglia can also increase levels of genes that improve the survival of brain cells. By chemically blocking the activity of microglia, researchers were able to reverse neuroprotection, which further supported the evidence.

Comment:

Findings from the study suggest a protective role of microglia through the ability to enhance the survival and functioning of brain cells. Targeting microglia may thus have therapeutic potential for progressive MS by potentially slowing neurodegeneration.  

Available therapies for MS work by reducing the inflammation that causes myelin damage. However, recent research has outlined the importance of remyelination, the process that involves repairing damaged myelin, and neuroprotection. Evidence has shown that these two processes are essential steps in preventing progression in MS. Further research on the roles of microglia in both inflammation and neuroprotection will be needed to understand how it influences MS disease.

Click here to read more about the role of microglia in MS in an MS Society-supported study published in the Journal of Interferon & Cytokine Research.

Source:

Chen Z et al. Microglial displacement of inhibitory synapses provides neuroprotection in the adult brain. Nature Communications 2014 July;5(4486).