Oligodendrocyte

Oligodendrocytes (from the Greek oligos 'little', dendron 'tree' and zytos 'cell') are glial cells and occur only in the central nervous system (CNS). They wrap the axons of nerve cells and form an electrically insulating myelin sheath . Unlike the peripherally occurring Schwann cells can in the white matter of multiple axons are isolated from a single oligodendrocytes of the CNS sections. In addition, oligodendrocytes also contribute to the energy supply of the axons.

origin

Oligodendrocytes are derived from oligodendrocyte progenitor cells . These occur in both the white and gray matter of the central nervous system (CNS). Oligodendrocyte progenitor cells make up about 6-8% of the total cells of the CNS. Differentiation to oligodendrocytes is possible throughout life.

morphology

The cell body of oligodendrocytes is around 6–8 µm in size. Oligodendrocytes have small, round cell nuclei with a high proportion of heterochromatin . They have few, slightly branched cellular processes, which form myelin myelin sheaths , which cover the cell processes ( axons ) of the nerve cells and thus electrically isolate them.

Compared to other glial cells such as astrocytes, oligodendrocytes can be distinguished from them by an electron-dense cytoplasm . In addition to typical organelles such as ribosomes , rough endoplasmic reticulum or Golgi apparatus , numerous microtubule filaments in particular are expressed as components of the cytoplasmic cytoskeleton . These are bundled in the cell processes, in the cell body without a superordinate spatial structure.

The plasma membrane of cultivated oligodendrocytes has been shown to contain neurotransmitter receptors that can trigger depolarization of the glial cells. An example of this are ionotropic glutamate receptors . Oligodendrocytes show similar sensitivity to the excitatory neurotransmitter glutamate as neurons, in which small increases in concentration already cause receptor-mediated cell death. Membrane growth inhibitors such as myelin-associated glycoprotein (MAG) and the proteoglycan Versican-2 are noticeable . Together with the glian scars formed by astrocytes , they are crucial inhibitors of neuron regeneration.

Oligodendrocyte-specific antigens

Oligodendrocyte-specific antigens are galactocerebroside , myelin basic protein (MBP), proteolipid protein (PLP), myelin oligodendrocyte glycoprotein (MAG), the oligodendrocyte-specific protein (OSP, new name claudin- 11) and the cyclic nucleotide phosphodiesterase (CNP).

Cell contacts

Intercellular contacts are crucial for the function of the oligodendrocytes. The contact surface of the myelin with the axon is subdivided into internodes , paranodes and juxtaparanodes, each of which is particularly molecularly specialized. The myelin-associated glycoprotein (MAG) and nectin-like (NECL) proteins are concentrated at the internodal contact surface . At the paranodies that limit the Ranvier cord rings , binding proteins ( contactin , contactin-associated protein) are arranged in a spiral , to which the ends of the myelin layer attach. In the area of the juxtaparanodium, numerous potassium channels are formed that serve for repolarization and thus maintain the resting membrane potential .

Clinical significance

There are numerous diseases that are associated with demyelination in the central nervous system, such as multiple sclerosis (MS), leukodystrophies and infantile cerebral palsy . In these clinical pictures, the targeted promotion of the formation of oligodendrocytes could also open up new therapeutic possibilities.

literature

Patricia Armati and Emily Mathey: The Biology of Oligodendrocytes . Cambridge University Press, Cambridge 2010, ISBN 978-1-139-49171-6 .

Individual evidence

^ Jan Behrends et al .: Dual Series Physiology . 3. Edition. Georg Thieme, Stuttgart 2016, ISBN 978-3-13-153163-6 , p. 36 .
↑ ^a ^b A. Lopez Juarez, D. He, Q. Richard Lu: Oligodendrocyte progenitor programming and reprogramming: Toward myelin regeneration. In: Brain Research . Volume 1638, Pt B05 2016, pp. 209-220, doi : 10.1016 / j.brainres.2015.10.051 , PMID 26546966 , PMC 5119932 (free full text) (review).
↑ ^a ^b Ulrich Welsch, Wolfgang Kummer: Histology - The textbook: cytology, histology and microscopic anatomy . 5th edition. Elsevier Health Sciences, 2018, ISBN 978-3-437-18366-9 , pp. 185 .
^ Helmut Kettenmann, Bruce R. Ransom: Neuroglia . Oxford University Press, 2005, ISBN 978-0-19-515222-7 , pp. 434 .
↑ J. Edwin Blalock: Neuroimmunoendocrinology . Karger Medical and Scientific Publishers, 1997, ISBN 978-3-8055-6524-0 , pp. 37 .
↑ Patricia Armati and Emily Mathey: The Biology of Oligodendrocytes . Cambridge University Press, Cambridge 2010, ISBN 978-1-139-49171-6 , pp. 75-76 .
↑ Gerhard Heldmaier, Gerhard Neuweiler: Comparative animal physiology: Neuro- and sensory physiology . Springer, Berlin 2013, ISBN 978-3-642-55699-9 , pp. 46 .

[1] Jan Behrends et al .: Dual Series Physiology . 3. Edition. Georg Thieme, Stuttgart 2016, ISBN 978-3-13-153163-6 , p. 36 .

[Juarez-2] A. Lopez Juarez, D. He, Q. Richard Lu: Oligodendrocyte progenitor programming and reprogramming: Toward myelin regeneration. In: Brain Research . Volume 1638, Pt B05 2016, pp. 209-220, doi : 10.1016 / j.brainres.2015.10.051 , PMID 26546966 , PMC 5119932 (free full text) (review).

[Welsch-3] Ulrich Welsch, Wolfgang Kummer: Histology - The textbook: cytology, histology and microscopic anatomy . 5th edition. Elsevier Health Sciences, 2018, ISBN 978-3-437-18366-9 , pp. 185 .

[4] Helmut Kettenmann, Bruce R. Ransom: Neuroglia . Oxford University Press, 2005, ISBN 978-0-19-515222-7 , pp. 434 .

[5] J. Edwin Blalock: Neuroimmunoendocrinology . Karger Medical and Scientific Publishers, 1997, ISBN 978-3-8055-6524-0 , pp. 37 .

[6] Patricia Armati and Emily Mathey: The Biology of Oligodendrocytes . Cambridge University Press, Cambridge 2010, ISBN 978-1-139-49171-6 , pp. 75-76 .

[7] Gerhard Heldmaier, Gerhard Neuweiler: Comparative animal physiology: Neuro- and sensory physiology . Springer, Berlin 2013, ISBN 978-3-642-55699-9 , pp. 46 .