Zebrafish as a translational regeneration model to study the activation of neural stem cells and role of their environment

The review is an overview of the current knowledgeof neuronalregenerationpropertiesin mammals andfish.The abilitytoregeneratethe damagedpartsof thenervoustissue has been demonstratedin all vertebrates.Notably,fishandamphibianshavethehighestcapacityforneurogenesis,whereasreptilesand birdsareabletoonlyregeneratespecific regionsof the brain,whilemammalshavereducedcapacityforneurogenesis.Zebrafish(Daniorerio)isapromisingmodelofstudybecauselesionsinthe brainor completecross-sectionof the spinal cordarefollowedbyaneffectiveneuro-regenerationthatsuccessfullyrestoresthe motorfunction. In the brainand thespinalcordof zebrafish,stemcellactivityis alwaysabletore-activatethe molecular programsrequiredfor centralnervoussystemregeneration.In mammals,traumaticbraininjuriesarefollowedby reducedneurogenesisandpooraxonalregeneration,ofteninsufficient tofunctionallyrestorethe nervoustissue, whilespinal injuriesarenotrepairedat all. The environmentthat surroundsthestemcellnicheconstitutedby connectivetissue and stimulatingfactors,includingpro-inflammationmolecules,seemstobeadeterminantintriggeringstemcellproliferationand/or the trans-differentiationof connectiveelements(mainlyfibroblasts).Investigatingand comparingtheneuronalregenerationinzebrafishandmammalsmaylead to a better understanding of the mechanisms behind neurogenesis, and the failure of the regenerative responsein mammals, first of all, the role of inflammation, consideredthe main inhibitorof the neuronalregeneration.