SHH and Stroke: For example, following ischemia there is an increase of Shh in the brain,23 and intrathecal administration of Shh in a stroke model has shown a neuroprotective effect.24 Similarly, Shh signaling is upregulated in reactive astrocytes following a focal freeze injury to the cerebral cortex.25 Moreover, this expression contributes to an increase in the proliferation of a subset of progenitor cells,25 suggesting that Shh signaling in the injured cortex directly influences precursor cells.