Object: Sonic hedgehog (Shh) is a glycoprotein molecule that has been shown to be associated with the proliferative capacity of endogenous neural precursor cells during embryonic development. It has also been shown to regulate the proliferative capacity of neural stem cells in the adult subventricular zone (SVZ), which are also upregulated in animal models of ischemic stroke. In the present study, the effects of exogenous administration of intrathecal Shh protein were examined in the setting of a rodent model of ischemic stroke, with particular attention given to endogenous neural stem cell proliferation and migration as well as inducible differences in behavioral recovery.
Methods: A rodent model of ischemic stroke was created using the intraluminal suture method of reversible middle cerebral artery occlusion. Animals were treated with intrathecal administration of Shh protein at 24 hours after the onset of the stroke. Behavioral testing was performed, and the animals were killed for measurements of infarct volume 7 days after stroke. Immunohistochemical staining was performed and measurements of cellular proliferation were obtained, with a focus on the proportion and distribution of neural progenitor cells in the SVZ. These values were compared across experimental groups.
Results: Treatment with intrathecal Shh protein resulted in significant improvement in behavioral function compared with the control group, with a significant reduction of ischemic tissue in the cerebral hemisphere. An increase of nestin immunoreactive cells was observed along the SVZ.
Conclusions: Intrathecal Shh agonist at doses that upregulate spinal cord GLI1 transcription increases the population of neural precursor cells after spinal cord injury in adult rats. Intrathecal administration of Shh protein appears to have a neuroprotective effect in animal models of ischemic stroke and is associated with improved behavioral recovery, which may be related to its effects on neurogenesis in the SVZ and could be associated with improved functional recovery.