WHAT ARE GLIA?
Glia are a collection of cells that are important for the development and healthy function of central nervous system (CNS) tissue in the brain and spinal cord. Glia together with neurons comprise the parenchymal unit (functional tissue) of the CNS.
urrently, glia are broadly classified into 3 main groups:
– Astrocytes – regulate neuron functions, synapse remodeling, regulate Blood Brain Barrier (BBB), and more.
– Microglia – regulate immune response in CNS, facilitate efficient clearance of cell debris and by-products created as part of normal functions.
– Oligodendroglia – regulate production and turn-over of myelin.
WHY ARE GLIA IMPORTANT?
The importance of glia in maintaining healthy CNS function is underscored by the fact that: (1) they are the primary responders to perturbations in normal CNS function; (2) their own dysfunction is implicated in the root cause of numerous diseases; and most importantly (3) regions of neural tissue that lose glia no longer maintain viable neural circuits.
Glia interact directly with neurons to:
– Establish and maintain proper synaptic connectivity.
– Facilitate synaptic pruning and remodeling.
– Clear neurotransmitters from the extra cellular space.
Example immunohistochemistry image shows glia interacting with neurons in the mouse hippocampus.
Glia interact directly with non-neural cells to:
– Regulate the Blood Brain Barrier (BBB) at CNS vessels.
– Regulate CNS parenchyma entry at the meninges.
Glia respond to CNS injury:
In traumatic CNS injury such as spinal cord injury (SCI) and stroke, the destruction of discrete volumes of neural tissue initiates a wound healing response coordinated by locally surviving glia responders. These glia react to injury by proliferating, migrating and synthesizing new biomolecules in a coordinated manner to constrain and isolate a non-neural lesion core from adjacent viable neural tissue. This dynamic process is exemplified below for a stroke lesion, where astrocytes (green) respond to isolate a non-neural lesion core (red) from viable neurons (magenta) over a 42 day (d) time course.