Astrocytes or astroglia are the star shaped glial cells that reside in the brain and spinal cord. They are the most numerous cells in the human brain, performing many tasks including support of the cells that comprise the blood-brain barrier as well as maintaining the extracellular ion balance, supplying nutrients to the nerve tissue and aiding in post-traumatic repair and scarring processes. In addition, astrocytes perform signaling tasks similar to neurons utilizing calcium ions and transmitter-molecules.
Role of Astrocytes in the Central Nervous System:
Astrocytes or astrocytic glial cells collectively form astroglia, star-shaped cells surrounding neurons in the brain and spinal cord, outnumbering neurons 50:1, and are very active in the Central Nervous System, and not, as previously through, mainly “filler” cells. Non neuronal cells in the nervous system are glial cells, and astrocytes constitute a subtype of this category. They serve to maintain, support, and repair the nervous tissue that they serve, and are responsible, in large part, for the plasticity of the nervous system. They also modulate synaptic transmission by making and releasing glutamate, the principle excitatory neurotrans, and their many process often envelope neural synapses. Research suggests that astrocytes communicate with neurons through the release of transmitters, known as gliotransmitters, through a calcium ion dependent mechanism.
Astrocytes respond to central nervous system (CNS) injury or disease via the process called reactive astrogliosis. This pathology has become a characteristic of nervous system structural lesions, and is a major area of current research. Astrocytes have been identified as involved in the pathologies of Huntington’s disease, Alzheimer’s disease, concussions, stroke, and CNS infections. Current research indicates that reactive astrogliosis plays a major role in many CNS disorders.
Fibrous, Protoplasmic, and Radial Astrocytes:
There are three forms of astrocytes in the CNS. These are, fibrous, protoplasmic, and radial astrocytes. Fibrous astroglia are generally found in white matter, have few organelles, and long unbranched processes. Protoplasmic glia have a huge quantity of organelles relative to fibrous cells, with short and highly branched cellular processes. They are generally found in gray matter. Radial astroglia exist at the intersection of gray matter and the pia mater, which is the innermost layer of the membranes surrounding the brain and spinal cord. Radial glia are also found in the vertebrate eye, where they form the Mueller Cells of the retina, and as Bergmann glia, epithelial cells in the cerebellum. are part of the radial glial cells.
Many primary astrocytes express GFAP, the intermediate filament glial fibrillary acidic protein, a characteristic trait.
Astrocyte Research Articles and References:
Characterization of astrocyte cells in response to stimuli: This study developed a protocol to prepare rat astrocytes in culture and then measured their response to chemical stimuli. Among the stimuli tested were hydrogen peroxide exposure, resveratrol (and its ability to protect from oxidation), and endotoxin exposure. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0060282
Use of astrocytes as a substrate for other neural cells: Researchers found that survival of CNS cells is improved when they are cultured atop a confluent layer of astrocytes. They have developed a protocol that selects for type I astrocytes in a confluent layer, and successfully plated dorsal root ganglion/dorsal horn co-cultures on top of them. http://cshprotocols.cshlp.org/content/2009/8/pdb.prot5273.full.pdf+html