Anatomy and Physiological aspects of glial cells, Role in Health and Disease

2. Neuroglia
•
•
Outnumber neurons by about
10 to 1 (the guy on the right had an inordinate
amount of them).
6 types of supporting cells
–
4 are found in the CNS:

3. Road Map for the session
• Introduction
• Classification – Types, Functions
• Pathophysiology
• Glial Cells in Disease

4. Road Map for the session
• Introduction
• Classification – Types, Functions
• Pathophysiology
• Glial Cells in Disease

5. The central nervous system consists of neurons and glial cells.
Neurons constitue about half the volume of the CNS and glial
cells make up the rest.
Glial cells provide support and protection for neurons. They
are thus known as the "supporting cells" of the nervous system.

6. Glia cells
•Although glia cells DO NOT carry nerve impulses (action
potentials) they do have many important functions. In fact,
without glia, the neurons would not work properly!
Astrocytes, like most glial cells, were long considered
essential for their role in supporting and maintaining
nerve tissue. But more and more evidence indicates that
astrocytes may actually play a far more important role in
neural communication

7. The four main functions of glial cells are:
- to surround neurons and hold them in place
- to supply nutrients and oxygen to neurons
- to insulate one neuron from another
- to destroy and remove the carcasses of dead neurons
(clean up)

8. Function of glia cells
Some glia function primarily as physical support for neurons. Others
regulate the internal environment of the brain, especially the fluid
surrounding neurons and their synapses, and provide nutrition to nerve
cells.
Glia have important developmental roles, guiding migration of neurons
in early development, and producing molecules that modify the growth
of axons and dendrites.
Recent findings in the hippocampus and cerebellum have indicated that
glia are also active participants in synaptic transmission, regulating
clearance of neurotransmitter from the synaptic cleft, releasing factors
such as ATP which modulate presynaptic function, and even releasing
neurotransmitters themselves.

9. Road Map for the session
• Introduction
• Classification – Types, Functions
• Pathophysiology
• Glial Cells in Disease

10. Neuroglia (Neuroglial Cells)
Neuroglia (Neuroglial Cells)
Central Neuroglia
Astrocyte
protoplasmic astrocyte
fibrous astrocyte
Oligodendrocyte
perineuronal satellite cell
interfascicular cell
Microglia
Ependymal Cell
Peripheral Neuroglia
Schwann Cell
in peripheral nerve
and ganglion
Capsular (Satellite) Cell
in ganglion

11. Gliogenesis

12. Microgliogenesis

13. Central Neuroglia
Astrocyte
Oligodendrocyte
Microglia

14. Astrocytes

15. Astrocytes

16. Astrocytes (astroglia) “star-cells”
Most numerous cell type in brain
Constitute ~30-50% of brain volume
NORMAL FUNCTIONS
Developmental: Migrational and
Axon guidance of neurons
Homeostasis of neuronal
microenvironment
Ionic
Metabolic
Neurotransmitter uptake
Blood-Brain barrier: induction and
maintenance
Trophic support of neurons (growth
factors)
Synaptogenesis and synaptic
remodeling

17. Astrocytes

18. Astrocytes
• Astrocytes contact virtually
every cell component in brain
• Other astrocytes (gap junctions)
• Ependymal cells
• Neurons (somas, processes, synapses)
• Oligodendroglia
• Capillary endothelial cells

19. stem cells of the adult brain?
astrocytes
The subventricular
zone
Ependymal cells
astrocytes
June 15, 1999
Brain Stem Cell Is Discovered,
Twice
By NICHOLAS WADE
Dr Arturo Alvarez-Buylla and Dr
Jonas Frisen report discovering site
in brain of elusive neural stem cell,
founding cell from which perhaps
whole brain develops, but each
scientist has a different site in
mind; Frisen contends that neural
stem cells are cells that line
ventricles, while Buylla contends
neural stem are the star-shaped
cells called astrocytes that lie one
layer in from ventricle lining;
experts say their contradictory
findings may yet be reconcilable
Johansson et al., "Identification of a neural stem cell in the adult mammalian central nervous system," Cell, 96:25-34, 1999.
Doetsch et al., "Subventricular zone astrocytes are neural stem cells in the adult mammalian brain," Cell, 97:703-16, 1999.

21. Astrocytes control synapse formation
Control of Synapse Number by Glia
Erik M. Ullian, Stephanie K.
Sapperstein, Karen S. Christopherson,
and Ben A. Barres
Science 2001 January 26; 291: 657-661.

22. Astrocytes communicate with each other,
other glia, and neurons via intercellular
calcium waves
Calcium Waves in Retinal Glial
Cells
Eric A. Newman and Kathleen R. Zahs
Science 1997 February 7; 275: 844-847.

23. Astrocyte
Astrocyte
• Protoplasmic Astrocyte: Gray Matter
• Fibrous Astrocyte: White Matter
Cell Body
‘potato’ shape nucleus, scarse pale cytopasm
Processes
- GFAP (glial fibroacidic protein): intermediate filament
- Perivascular Feet (Foot Process, Vascular End-Feet)
surrounding blood vessels
Specialized Astrocytes
- Bergmann’s gial cell, Muller cell, pituicyte

24. Astrocyte in association with a blood vessel

26. Oligodendrocytes

27. Myelination in CNS
12-27

28. Myelination in PNS
• Myelination begins during
fetal development, but
proceeds most rapidly in
infancy.
12-28

29. Oligodendrocyte

30. Oligodendroglia
• “few-branch” glia
• Discovered by del Rio-Hortega, using metallic impregnation
techniques in 1921
• one oligo myelinates many CNS axons
• CNS myelinators (white matter)
• Target of autoimmune attack in MS
• Specific oligodendrocyte myelin proteins:
– PLP
– DM20
– MBP

31. Ultrastructure of white matter

32. Microglia
The Brain’s
Immune Cell

33. Microglia’s
Immune Response
* Resting microglia in normal brain,
called ramified or resting
* Normally not Phagocytic
* Under some pathological condition,
like trauma, stroke or Alzheimer’s;
neurodegeneration occurs.
* Microglia become activated and
engulf the apoptotic cell, and
changing it’s shape to ameboid.

34. Identifing Microglia
A specific histochemical marker (lectin Ricinus communis
agglutini-1) for normal human microglia
H. Mannoji, H. Yeager, & L.E. Becker
Hypothesis
Microglia in normal human
brain can be specifically
demonstrated using the
lectin RCA-1, as detected
with the avidin-biotin
peroxidase method

35. Microglia
Microglia
Cell Body
slender, indented, heterochromatic nucleus
dark cytopasm
- prominent secondary lysosome
Processes
short, highly branched
Macrophage (Mononuclear Phagocytic) System
Mesenchymal Origin - Blood Monocyte
Increased in Inflammation

36. Ependymal Cell
Ependymal Cell
Epithelial Cell
lining ventricular surface
cilia and microvilli on luminal surface
simple cuboidal cell with round nucleus
Tanicyte
basal process, numerous in 3rd ventricle
most ependymal cell has basal process
(Chung & Lee, 1988)
Choroid Plexus Epithelial Cells
ion transporting cell: numerous mitochondria

38. Figure 12.6 An Introduction to
Neuroglia
Figure 12.6

39. Road Map for the session
• Introduction
• Classification – Types, Functions
• Pathophysiology
• Glial Cells in Disease

40. Pathophysiology

42. Astrocytes in Disease:
Gliosis
• Prominent expression of
intermediate filaments: “Glial
filaments”:
• Glial Fibrillary Acidic Protein
(discovered as a major component of
Multiple Sclerosis White Matter
Plaques;)
• Also, vimentin, nestin
MS plaque: GFAP

43. More reactive astrocytes
(gliosis)

49. Road Map for the session
• Introduction
• Classification – Types, Functions
• Pathophysiology
• Glial Cells in Disease

50. Specific Conditions
• Stroke

55. Specific Conditions
• Stroke
• Cerebral Oedema

57. Specific Conditions
• Stroke
• Cerebral Oedema
• AD

59. Specific Conditions
• Stroke
• Cerebral Oedema
• AD
• Neuropathic Pain

61. Specific Conditions
• Stroke
• Cerebral Oedema
• AD
• Neuropathic Pain
• Epilepsy

63. Specific Conditions
• Stroke
• Cerebral Oedema
• AD
• Neuropathic Pain
• Epilepsy
• Glioma

66. Summary
• Introduction
• Classification – Types, Functions
• Pathophysiology
• Glial Cells in Disease

67. Specific Conditions
• Stroke
• Cerebral Oedema
• AD
• Neuropathic Pain
• Epilepsy
• Glioma