Oligodendrocytes

Oligodendrocytes are glial cells in the central nervous system responsible for forming and maintaining the myelin sheath that surrounds axons. Myelination in the CNS increases conduction velocity through saltatory conduction.

Oligodendrocytes derive from oligodendrocyte precursor cells (OPCs), which originate from neural stem cells in the ventricular zone during development. OPCs express markers such as PDGFRα and NG2, and differentiate into mature oligodendrocytes that express myelin proteins including myelin basic protein (MBP) and proteolipid protein (PLP).

Anatomy and myelination: A mature oligodendrocyte has a small cell body with multiple processes that extend to numerous axons. Each process wraps around segments of axons to form the myelin sheath. In the CNS, one oligodendrocyte can extend processes to several axons, forming many myelin segments (internodes) on different nerves, unlike Schwann cells in the peripheral nervous system which ensheath a single axon segment.

Structure and nodes: The myelin sheath is lipid-rich and arranged in compacted layers with periodic gaps forming nodes of Ranvier, which are essential for rapid saltatory conduction.

Function: Myelin increases membrane resistance and decreases capacitance, accelerating action potential conduction. Oligodendrocytes also contribute to metabolic support of axons, transferring lactate and other metabolites via gap junctions.

Clinical relevance: Demyelination caused by autoimmune processes or injury (notably in multiple sclerosis) disrupts conduction and leads to neurological deficits. Remyelination can occur via OPC recruitment and differentiation, although efficacy may decline in chronic disease.

Development and turnover: Oligodendrocytes are generated throughout life from OPCs; mature oligodendrocytes contribute to ongoing myelination and repair in the CNS.