Background: Administration of neural stem cell (NSC) into peri-infarct region is a promising treatment to improve the outcome after brain ischemia. However, whether the survival of implanted NSC is influenced by endogenous neuronal activity remains unclear. Using optogenetic technique, we regulated the activity of striatal neuron and investigated whether the excitation or the inhibition of striatal neuronal activity could improve NSC survival and overall neurological outcome.
Methods: Adeno-assosiated virus carrying ChR2 or ArchT gene under the control of promoter CaMKII was injected into mice striatum two weeks before the surgery of 60 minutes transient middle cerebral artery occlusion (tMCAO). NSCs cultured from transgenic mice expressing fluorescent protein or isometric phosphate buffer saline was transplanted into peri-infarct region at striatum at 4 days after tMCAO. The striatal neurons were stimulated 15 minutes daily by 473nm pulse or 530nm constant laser via implanted optical fiber from 7 to 13 days after tMCAO. Neurological severity score (NSS) was assessed at 3 and 14 days. After sacrificing the animals at 14 days after tMCAO, brain infarct volume was measured with cresyl violet staining. The fluorescence intensity and the diffuse area of implanted NSC were calculated to evaluate the survival of NSC.
Results: Mice received NSC transplantation and optogenetic inhibition showed smaller infarct volume compared to that only received NSC transplantation or PBS (p<0.05). The fluorescence diffuse area of transplanted NSC was larger in mice with optogenetic inhibition than that without optogenetic inhibition (p<0.05). Mice received NSC transplantation and optogenetic excitation had larger infarct volume and higher NSS than mice only received NSC transplantation (p<0.05), but showed no differences compared to mice received PBS (p>0.05). The fluorescence diffuse area and the mean optical density of transplanted NSC was smaller in mice with optogenetic excitation than that without optogenetic excitation (p<0.05).
Conclusion: Inhibition of striatal neuronal activity at sub-acute phase after ischemia can improve the treatment of implanted NSC. To the opposite, excitation of striatal neuronal activity can reduce the NSC treatment.