Overview

Schwann cells are essential glial cells that primarily reside in the peripheral nervous system, where they form intimate relationships with axon to support neural function. Named after physiologist Theodor Schwann, these cells are crucial for both the development and maintenance of peripheral nerves.

Structure and Types

There are two main types of Schwann cells:

1. Myelinating Schwann Cells

   • Wrap multiple layers of myelin around single axons
   • Form distinct segments called internodes
   • Create gaps (nodes of Ranvier) between myelin segments
   • Maintain a 1:1 relationship with their associated axon

2. Non-myelinating Schwann Cells

   • Surround multiple small-diameter axons
   • Form Remak bundles
   • Provide metabolic support without creating myelin

Functions

Primary Roles

1. Myelination

   • Production and maintenance of myelin sheaths
   • Enhancement of action potential conduction
   • Support of saltatory conduction

2. Neuronal Support

   • Provision of metabolic support to axons
   • Regulation of ion concentrations
   • Production of neurotrophic factors

3. Repair and Regeneration

   • Guide nerve regeneration after injury
   • Form Büngner bands during repair
   • Phagocytose cellular debris

Development

Schwann cells originate from the neural crest and undergo several developmental stages:

1. Schwann cell precursors
2. Immature Schwann cells
3. Pro-myelinating Schwann cells
4. Mature myelinating or non-myelinating cells

Clinical Significance

Disorders

Several conditions involve Schwann cell dysfunction:

• Charcot-Marie-Tooth disease
• Guillain-Barré syndrome
• schwannoma (tumors)
• peripheral neuropathy

Therapeutic Applications

Schwann cells are important targets for:

• nerve repair
• cell therapy
• neuropathy treatment

Research Directions

Current areas of investigation include:

• axon-glial interaction
• remyelination
• neural regeneration
• bioengineering applications

Comparison with CNS Glia

While Schwann cells myelinate PNS axons, oligodendrocytes serve an analogous function in the central nervous system:

• Schwann cells: one cell per axon segment
• Oligodendrocytes: multiple axon segments per cell
• Different regenerative capabilities
• Distinct molecular markers

Molecular Biology

Key molecules involved in Schwann cell function:

• neuregulin-1 signaling
• myelin proteins
• transcription factors
• cell adhesion molecules

Understanding Schwann cell biology continues to be crucial for developing treatments for peripheral nerve disorders and advancing regenerative medicine strategies.