Poststroke Sonic Hedgehog Agonist Treatment Improves Functional Recovery by Enhancing Neurogenesis and Angiogenesis

Background And Purpose: Because of the limitation in treatment window of the r-tPA (recombinant tissue-type plasminogen activator), the development of delayed treatment for stroke is needed. In this study, we examined the efficacy of delayed poststroke treatment (post 3-8 days) of the sonic hedgehog pathway agonist on functional recovery and the underlying mechanisms.

Methods: We evaluated functional recovery at 1 month after stroke using locomotion analysis and Barnes maze test for cognitive function. We used a genetically inducible neural stem cell-specific reporter mouse line (nestin-CreERT2-R26R-YFP) to label and track their proliferation, survival, and differentiation in ischemic brain. Brain tissue damage, angiogenesis, and cerebral blood flow recovery was evaluated using magnetic resonance imaging techniques and immunostaining.

Results: Our results show that delayed treatment of sonic hedgehog pathway agonist in stroke mice results in enhanced functional recovery both in locomotor function and in cognitive function at 1 month after stroke. Furthermore, using the Nestincre-ERT2-YFP mice, we showed that poststroke sonic hedgehog pathway agonist treatment increased surviving newly born cells derived from both subventricular zone and subgranular zone neural stem cells, total surviving DCX+ (Doublecortin) neuroblast cells, and neurons (NeuN+/YFP+) in the ischemic brain. Sonic hedgehog pathway agonist treatment also improved the brain tissue repair in ischemic region supported by our T2-weighted magnetic resonance imaging, cerebral blood flow map by arterial spin labeling, and immunohistochemistry (α-smooth muscle actin and CD31 immunostaining).

Conclusions: These data confirm an important role for the hedgehog pathway in poststroke brain repair and functional recovery, suggesting a prolonged treatment window for potential treatment strategy to modulate sonic hedgehog pathway after stroke.