1. Neuroglia and Myelin Dr. Raymond Colello

2. Glia Cell Classes Two Major Classes of Glia 1.) Macroglia Astrocytes
Oligodendrocytes
Ependymal Cells
2.) Microglia

3. Function of Glia Cells Astrocytes - Structural support
- Induce tight junction formation by endothelial cells
- Guide neuroblast migration and axon growth
- Take up neurotransmitters within synaptic regions
- Take up excess K+ released during high neuronal activity
- Form a glial scar after CNS lesion
Oligodendrocytes
- Ensheath CNS axons with myelin
- Locally regulate axon size
- Stabilize axon numbers in a developing pathway
Microglia
- Serve as brain macrophages
-Regulate astrocytes during development and injury
Schwann Cells
- Ensheath PNS axons with myelin

4. Distribution of glial cells in the CNS

5. Glial Cell Lineage
MBP-positive
A2B5-positive
GFAP-positive

6. Growth factors control glial cell diversification
O-2A: Oligodendrocyte-
Type 2 Astrocyte
PDGF: Platelet-derived
growth factor
CNTF: Ciliary neurotrophic
factor

7. Distribution of glial cells in the CNS

8. Astrocytes form the glial limiting membrane
Outer surface of CNS
Phase Micrograph Immunostain for GFAP

9. Astrocytes establish blood brain barrier by inducing tight junction formation
Blood Vessel----
GFAP staining

10. Astrocytes guide neuroblasts to final destination
---Cerebellum
---Hippocampus

11. Astrocytes guide the migration of neuroblasts
Molecular Layer
Granule cell Layer
GFAP Immunostain

12. Guiding neuroblast migration

13. Astrocytes take up excess K+ during high neuronal activity

14. Astrocytes form gliotic scar following CNS injury
MRI of Spinal Cord
Injury
Green: GFAP
Red: Chondroitin Sulfate Proteoglycans

15. Function of Glia Cells Astrocytes - Structural support
- Induce tight junction formation by endothelial cells
- Guide neuroblast migration and axon growth
- Take up neurotransmitters within synaptic regions
- Take up excess K+ released during high neuronal activity
- Form a glial scar after CNS lesion
Oligodendrocytes
- Ensheath CNS axons with myelin
- Locally regulate axon size
- Stabilize axon numbers in a developing pathway
Microglia
- Serve as brain macrophages
-Regulate astrocytes during development and injury
Schwann Cells
- Ensheath PNS axons with myelin

16. Oligodendrocytes myelinate CNS axons
Oligodendrocytes can wrap up to 50 axons with myelin
Each myelin sheath is made of up to 100 turns of myelin

17. Relationship between oligodendrocyte perikaryon and an unrolled myelin internode

18. Immunocytochemical distribution of myelin proteins
MBP: 30% of total protein
PLP: 50% of total protein
CNP: 5% of total protein
MAG: 1% of total protein

19. Conduction velocity Myelinated versus Unmyelinated
A 4µm myelinated axons conducts at the same
speed at a .5mm unmyelinated axon

20. Propagation of nerve impulse
Unmyelinated axons exhibit continuous conduction whereas
myelinated axons exhibit saltatory conduction

21. Destruction of oligodendrocytes leads to demyelinating diseases
Plaque
Demyelinated plaques found in the dorsal columns
Of the spinal cord

22. Does the CNS have the capacity to regenerate?

23. Testing the peripheral and central nervous system environment
Axons of CNS neurons will
grow through peripheral nerve
bridge but will not enter CNS
bridge.
Something n the CNS is inhibitory
for neurite outgrowth.

24. Testing inhibitory properties of CNS cells
RGC’s on astrocytes RGC’s on oligodendrocytes

25. Identifying myelin inhibitor

26. Neutralizing oligodendrocyte inhibitor promotes regeneration
  Recovery from spinal cord injury mediated by antibodies to neurite growth inhibitors. Bregman BS, Kunkel-Bagden E, Schnell L, Dai HN, Gao D, Schwab ME
Nature Nov 30;378(6556):
Nature Jan 27;403(6768):434-9.
Nogo-A is a myelin-associated neurite outgrowth inhibitor and an antigen for monoclonal antibody IN-1. Chen MS, Huber AB, van der Haar ME, Frank M, Schnell L, Spillmann AA, Christ F, Schwab ME.

27. Know the different classes of glial cells and what are their
distinguishing features
Know glial cell lineage and the growth factors associated with
glial cell differentiation
Know glial cell function
Know why the CNS shows little regenerative capacity