RESUMO
Hypertrophic scarring and poor intrinsic axon growth capacity constitute major obstacles for spinal cord repair. These processes are tightly regulated by microtubule dynamics. Here, moderate microtubule stabilization decreased scar formation after spinal cord injury in rodents through various cellular mechanisms, including dampening of transforming growth factor-ß signaling. It prevented accumulation of chondroitin sulfate proteoglycans and rendered the lesion site permissive for axon regeneration of growth-competent sensory neurons. Microtubule stabilization also promoted growth of central nervous system axons of the Raphe-spinal tract and led to functional improvement. Thus, microtubule stabilization reduces fibrotic scarring and enhances the capacity of axons to grow.
Assuntos
Axônios/fisiologia , Cicatriz/prevenção & controle , Microtúbulos/metabolismo , Paclitaxel/administração & dosagem , Traumatismos da Medula Espinal/tratamento farmacológico , Traumatismos da Medula Espinal/fisiopatologia , Regeneração da Medula Espinal , Animais , Células Cultivadas , Proteoglicanas de Sulfatos de Condroitina/metabolismo , Cicatriz/patologia , Feminino , Gânglios Espinais/citologia , Cinesinas/metabolismo , Microtúbulos/efeitos dos fármacos , Paclitaxel/farmacologia , Transporte Proteico , Ratos , Ratos Sprague-Dawley , Células Receptoras Sensoriais/fisiologia , Transdução de Sinais , Proteína Smad2/metabolismo , Medula Espinal/citologia , Medula Espinal/efeitos dos fármacos , Traumatismos da Medula Espinal/patologia , Fator de Crescimento Transformador beta/metabolismoRESUMO
A major barrier to regeneration of CNS axons is the presence of growth-inhibitory proteins associated with myelin and the glial scar. To identify chemical compounds with the ability to overcome the inhibition of regeneration, we screened a novel triazine library, based on the ability of compounds to increase neurite outgrowth from cerebellar neurons on inhibitory myelin substrates. The screen produced four "hit compounds," which act with nanomolar potency on several different neuronal types and on several distinct substrates relevant to glial inhibition. Moreover, the compounds selectively overcome inhibition rather than promote growth in general. The compounds do not affect neuronal cAMP levels, PKC activity, or EGFR (epidermal growth factor receptor) activation. Interestingly, one of the compounds alters microtubule dynamics and increases microtubule density in both fibroblasts and neurons. This same compound promotes regeneration of dorsal column axons after acute lesions and potentiates regeneration of optic nerve axons after nerve crush in vivo. These compounds should provide insight into the mechanisms through which glial-derived inhibitors of regeneration act, and could lead to the development of novel therapies for CNS injury.
