In response to TBI, astrocytes in different cellular microenvironments tune their reactivity to varying degrees of axonal injury, vascular disruption, ischemia and inflammation.
TBI-reactive astrocytes significantly contribute to post-traumatic tissue repair and synaptic remodeling following brain trauma
.
What do astrocytes repair?
Astrocytes outnumber neurons in the human brain, and they play a key role in numerous functions within the central nervous system (CNS), including glutamate, ion (i.e., Ca
2 +
, K
+
) and water homeostasis, defense against oxidative/nitrosative stress, energy storage, mitochondria biogenesis, scar formation,
tissue repair
…
Do astrocytes repair damage?
However,
astrocytes are also capable of producing factors to support repair and regeneration after CNS damage
(Kim et al., 2010; Madathil et al., 2013).
Do astrocytes form neural scar tissue?
Reactive astrocytes are the main cellular component of the glial scar
. After injury, astrocytes undergo morphological changes, extend their processes, and increase synthesis of glial fibrillary acidic protein (GFAP).
What happens if astrocytes are damaged?
Astrocytes are less vulnerable than neurons to ischemic injury but they are damaged if there is lactic acidosis. Such damage causes
intracellular fluid accumulation (cytotoxic edema)
.
How do astrocytes help neurons?
Astrocytes have long been considered as just providing trophic support for neurons in the central nervous system, but recently several studies have highlighted their importance in many functions such as
neurotransmission, metabolite and electrolyte homeostasis, cell signaling, inflammation, and synapse modulation
.
What function do astrocytes play in the CNS?
They have a
regulatory role of brain functions that are implicated in neurogenesis and synaptogenesis, controlling blood–brain barrier permeability and maintaining extracellular homeostasis
. Mature astrocytes also express some genes enriched in cell progenitors, suggesting they can retain proliferative potential.
Do astrocytes guide neuron development?
Astrocytes constitute the majority of glial cells in the CNS.
Astrocyte-derived factors have essential effects to promote neuronal development
. Wnt3 released by astrocytes regulate neural stem cell differentiation through Wnt/β-catenin signal pathways (Kuwabara et al., 2009).
What is the function of oligodendrocytes?
In the central nervous system (CNS), oligodendrocytes assemble myelin, a multilayered sheath of membrane, spirally wrapped around axonal segments and best known for its role in
enabling fast saltatory impulse propagation
1 , 2
.
What are the two functions of astrocytes?
Functions of astrocytes include
physical and metabolic support for neurons
, detoxification, guidance during migration, regulation of energy metabolism, electrical insulation (for unmyelinated axons), transport of blood-borne material to the neuron, and reaction to injury.
What is the function of astrocytes quizlet?
Describe the function of an astrocyte. They are branched glial cells that
nourish neurons and provide a barrier between nervous tissue and blood
. Responsible for blood-brain barrier to protect against blood borne infections.
Does gliosis go away?
Diffuse traumatic injury can result in diffuse or more moderate gliosis without scar formation. In such cases,
gliosis may also be reversible
. In all instances of gliosis resulting from CNS trauma, the long-term clinical outcome is highly dependent on the degree of astrogliosis and scar formation.
What triggers gliosis?
Gliosis is
a reaction of the CNS to injury of the brain or spinal cord
. Although subtle changes occur earlier, gliosis is usually appreciated by two to three weeks after an injury. Nearly any injury of the CNS can cause gliosis, so its presence is not diagnostic of a specific pathologic entity (see Table 20.2).
Where do astrocytes come from?
Astrocytes are derived from
heterogeneous populations of progenitor cells in the neuroepithelium of the developing central nervous system
. There is remarkable similarity between the well known genetic mechanisms that specify the lineage of diverse neuron subtypes and that of macroglial cells.
What would happen if astrocytes are damaged or stopped functioning?
Pretty much everything happening in the brain would fail without astrocytes
. These star-shaped glia cells are known to have a critical role in synapse creation, nervous tissue repair, and the formation of the blood-brain barrier.
What happens when astrocytes are activated?
Another major function of these astrocytes involves their activation in response to damage. Astrocyte activation, or astrogliosis,
plays a central role in the response to most or all neurological insults including trauma, infections, stroke, tumorigenesis, neurodegeneration, and epilepsy
.
What important mechanism of brain support and protection is maintained by astrocytes?
There are at least seven distinct mechanisms by which astrocytes protect neurons from damage; these are (1)
protection against glutamate toxicity
, (2) protection against redox stress, (3) mediation of mitochondrial repair mechanisms, (4) protection against glucose-induced metabolic stress, (5) protection against iron …
How do astrocytes communicate with neurons?
Astrocytes communicate with adjacent astrocytes
via gap junctions (GJ) and with distant astrocytes via extracellular ATP
. The rise in Ca
2 +
causes release of glutamate from astrocytes, and ATP is released via an unknown mechanism, which propagates ATP signaling to adjacent cells.
Do astrocytes provide defense for the CNS?
The statement that does not describe a function of astrocytes is c)
Provide the defense for the CNS
. Astrocytes are glial cells of the central nervous system (CNS) that perform the functions described in answers ‘a’, ‘b’, ‘d’, and ‘e’. Microglial cells are phagocytic cells that provide defense for the CNS.
Where are astrocytes found in CNS?
Protoplasmic astrocytes are found
throughout the grey matter in the brain
, which is where the majority of neurons are located. The grey matter in the brain controls functions such as muscle control and sensory perception, including speech, taste, sense of smell, memory, judgment, and more.
How do astrocytes maintain brain homeostasis?
Astrocytes are the most abundant cell type in the brain and contribute to brain homeostasis in several ways, including
buffering of extracellular K+, regulating neurotransmitter release, forming the blood-brain barrier (BBB), releasing growth factors, and regulating the brain immune response
.
Do astrocytes form myelin sheath?
Astrocytes Provide Lipids for Myelin Sheath Production
Still consistent with their implication in myelination, astrocytes were also proposed to supply lactate to oligodendrocytes. Lactate constitutes a source of energy and a precursor of lipid synthesis including cholesterol altogether necessary for myelin production.
How do astrocytes differ from neurons?
Astrocytes are specialized glial cells that
outnumber neurons by over fivefold
. They contiguously tile the entire central nervous system (CNS) and exert many essential complex functions in the healthy CNS.
Do astrocytes clean up debris?
These results suggested that
astrocytes remove cell debris
in order to protect surrounding healthy neurons from the toxic materials released by the dead and dying cells.
