Schwann Cell Plasticity in Peripheral Nerve Regeneration after Injury

Abstract

In the normal peripheral nervous system, Schwann cells (SCs) are present in two different states of differentiation: myelinating SCs that surround large-caliber axons, forming myelin sheath, and non-myelinating SCs that surround more small-caliber axons forming Remak bundles. Under pathological conditions (injury or inflammation), SCs, with a remarkable plasticity, undergo phenotypic transformations , downregulating the production of myelin proteins mRNAs, upregulating neurotrophic factors and cytokines, thus promoting the axonal regeneration. Dedifferentiated SCs activate the protein degradation, participating in the demy-elination process and clearance of myelin debris; attract macrophages helping wound healing; proliferate to replace lost cells; guide axonal growth; and protect against secondary axonal damage. Thus, SC functions have a critical contribution to regeneration processes that occur in peripheral nerve after injury.