Sensory Nerve Regeneration at the CNS-PNS Interface

Over a century ago, Ramon y Cajal, using the Golgi staining technique to label a subset of dorsal root ganglion (DRG) axons, showed that injured DR axons regenerate within the root but fail to re-enter the adult spinal cord. As shown in his drawing (Fig. 1), DR axons grow away from (arrow), or stop at (arrowheads), the junction between the CNS and PNS, termed the dorsal root entry zone (DREZ). Regeneration of dorsal root (DR) axons into spinal cord is prevented at the dorsal root entry zone (DREZ), the transitional zone between the CNS and PNS. Why regeneration fails at DREZ has remained an interesting issue both because dorsal root injuries are common and because DREZ serves as an excellent model system for studying the reasons for the failure of CNS regeneration.