Central nervous system regeneration: from leech to opossum

This review discusses how the central nervous system regenerates in leeches and neonatal opossums, contrasting it with the lack of regeneration in adult mammalian spinal cords. The aim is to identify cellular and molecular mechanisms that either promote or prevent regeneration. In leeches, individual axons can regrow successfully to re-establish connections, and microglial cells and nitric oxide play key roles in this process. In neonatal opossums, axons can grow across spinal cord lesions, but this ability stops abruptly between postnatal days 9 and 12, coinciding with changes in gene expression related to growth-promoting and growth-inhibitory molecules.

• 1
  Leech CNS regeneration involves microglial cells and nitric oxide, which facilitate axon regrowth and reconnection with appropriate synaptic targets.
• 2
  In neonatal opossums, the capacity for spinal cord regeneration ceases between postnatal days 9 and 12, correlating with the upregulation of growth-inhibitory molecules associated with myelin.
• 3
  Gene expression analysis in opossums revealed candidate molecules that either promote or prevent regeneration, including laminin receptors and growth-promoting molecules in regenerating spinal cords, and reticulon, myelin basic protein, and semaphorin receptors in non-regenerating spinal cords.