Lecture Notes: Myelination in Peripheral and Central Nervous Systems

Overview

• Topic: Myelination in the Peripheral Nervous System (PNS) and Central Nervous System (CNS)
• Importance of different culturing paradigms for peripheral vs. central neurons

Myelination Process in PNS

Schwann Cells

• Schwann cells are glial cells responsible for the myelination of peripheral neurons.
• They arrive at the axon and dendrites and divide upon contact.
• Schwann cells encircle the axon, forming a myelin sheath.
• Key protein secreted by Schwann cells: Myelin Basic Protein (MBP).
• The final structure resembles a complete sheet due to the merging of cell membranes.

Comparison with CNS

• The myelination process differs considerably between PNS and CNS.

Importance of Cell Culture Models

• Essential for studying myelination processes and disorders.
• Case study of John Wayne Ramsey's work on developing myelination in vitro.

Objectives of Research

1. Achieve myelination in a dish using peripheral neurons.
2. Create a test bed for studying myelinating disorders (e.g., multiple sclerosis).

Practical Aspects of Neuron Culturing

Requirements for Culturing Peripheral Neurons

• Source of Neurons: Dorsal Root Ganglionic Neurons (DRGs).
  • Best obtained from embryonic rats (E14).
• Surgical Extraction:
  • Requires microsurgery to isolate spinal cord and DRGs carefully.

Enzymatic Dissociation

• Method: Use trypsin or papain for dissociation.
• Important: Stop trypsin reaction after 10-15 mins with a trypsin inhibitor to prevent damage to cells.
• Result: Single cell suspension of DRG neurons.

Requirement for Schwann Cells

• Schwann cells must be obtained from a mature source.
• Best source: Postnatal rats (P1 to P4).
• Schwann cells are dividing cells, while the neurons are non-dividing.

Culturing Strategy

Initial Steps

1. Plate DRG neurons in a culture dish; observe them sending out processes within 24 hours.
2. As neurons grow, one process will develop into an axon.
3. Introduce Schwann cells during their growth phase (after two to three days).

Conclusion

• Discussion on the transition to adult hippocampal neurons will continue in future lectures.
• Emphasis on the interconnectedness of cell culture techniques and developmental biology.