Sonic hedgehog stimulates neurite outgrowth in a mechanical stretch model of reactive-astrogliosis

Sci Rep. 2016 Feb 23:6:21896. doi: 10.1038/srep21896.

Abstract

Although recovery following a stroke is limited, undamaged neurons under the right conditions can establish new connections and take on-board lost functions. Sonic hedgehog (Shh) signaling is integral for developmental axon growth, but its role after injury has not been fully examined. To investigate the effects of Shh on neuronal sprouting after injury, we used an in vitro model of glial scar, whereby cortical astrocytes were mechanically traumatized to mimic reactive astrogliosis observed after stroke. This mechanical trauma impaired neurite outgrowth from post-natal cortical neurons plated on top of reactive astrocytes. Addition of Shh to the media, however, resulted in a concentration-dependent increase in neurite outgrowth. This response was inhibited by cyclopamine and activated by oxysterol 20(S)-hydroxycholesterol, both of which modulate the activity of the Shh co-receptor Smoothened (Smo), demonstrating that Shh-mediated neurite outgrowth is Smo-dependent. In addition, neurite outgrowth was not associated with an increase in Gli-1 transcription, but could be inhibited by PP2, a selective inhibitor of Src family kinases. These results demonstrate that neurons exposed to the neurite growth inhibitory environment associated with a glial scar can be stimulated by Shh, with signaling occurring through a non-canonical pathway, to overcome this suppression and stimulate neurite outgrowth.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Astrocytes / cytology
  • Astrocytes / drug effects*
  • Astrocytes / metabolism
  • Cerebral Cortex / cytology
  • Cerebral Cortex / drug effects
  • Cerebral Cortex / metabolism
  • Coculture Techniques
  • Gene Expression Regulation
  • Gliosis / genetics
  • Gliosis / metabolism*
  • Gliosis / pathology
  • Hedgehog Proteins / antagonists & inhibitors
  • Hedgehog Proteins / genetics
  • Hedgehog Proteins / metabolism
  • Hedgehog Proteins / pharmacology*
  • Hydroxycholesterols / pharmacology
  • Mice
  • Mice, Inbred C57BL
  • Models, Biological
  • Neuronal Outgrowth / drug effects*
  • Neurons / cytology
  • Neurons / drug effects*
  • Neurons / metabolism
  • Pressure
  • Primary Cell Culture
  • Pyrimidines / pharmacology
  • Signal Transduction
  • Smoothened Receptor / genetics
  • Smoothened Receptor / metabolism
  • Stress, Mechanical
  • Veratrum Alkaloids / pharmacology
  • Zinc Finger Protein GLI1 / genetics
  • Zinc Finger Protein GLI1 / metabolism
  • src-Family Kinases / antagonists & inhibitors
  • src-Family Kinases / genetics
  • src-Family Kinases / metabolism

Substances

  • AG 1879
  • Gli1 protein, mouse
  • Hedgehog Proteins
  • Hydroxycholesterols
  • Pyrimidines
  • Shh protein, mouse
  • Smo protein, mouse
  • Smoothened Receptor
  • Veratrum Alkaloids
  • Zinc Finger Protein GLI1
  • 20-hydroxycholesterol
  • src-Family Kinases
  • cyclopamine