Background and Purpose Intravascular transplantation of neural stem cells represents a minimally invasive therapeutic approach for the treatment of central nervous system diseases. The cellular biodistribution after intravascular injection needs to be analyzed to determine the ideal delivery modality. We studied the biodistribution and efficiency of targeted central nervous system delivery comparing intravenous and intra-arterial (IA) administration of neural stem cells after brain ischemia. Methods Mouse neural stem cells were transduced with a firefly luciferase reporter gene for bioluminescence imaging (BLI). Hypoxic–ischemia was induced in adult mice and reporter neural stem cells were transplanted IA or intravenous at 24 hours after brain ischemia. In vivo BLI was used to track transplanted cells up to 2 weeks after transplantation and ex vivo BLI was used to determine single organ biodistribution. Results Immediately after transplantation, BLI signal from the brain was 12 times higher in IA versus intravenous injected animals (P<0.0001). After IA injection, 69% of the total luciferase activity arose from the brain early after transplantation and 93% at 1 week. After intravenous injection, 94% of the BLI signal was detected in the lungs (P = 0.004) followed by an overall 94% signal loss at 1 week, indicating lack of cell survival outside the brain. Ex vivo single organ analysis showed a significantly higher BLI signal in the brain than in the lungs, liver, and kidneys at 1 week (P<0.0001) and 2 weeks in IA (P = 0.007). Conclusion IA transplantation results in superior delivery and sustained presence of neural stem cells in the ischemic brain in comparison to intravenous infusion.

Alzheimer’s disease (AD) is a chronic neurodegenerative disease, which is characterized by cognitive and synaptic plasticity damage. Rapamycin is an activator of autophagy/mitophagy, which plays an important role in identifying and degrading damaged mitochondria. The aim of this study was to investigate the effect of rapamycin on cognitive and synaptic plasticity defects induced by AD, and further explore if the underlying mechanism was associated with mitophagy. The results show that rapamycin increases parkin-mediated mitophagy and promotes fusion of mitophagosome and lysosome in the APP/PS1 mouse hippocampus. Rapamycin enhances learning and memory viability, synaptic plasticity and the expression of synapse related proteins, and impedes Cytochrome C-mediated apoptosis, decreases oxidative status and recovers mitochondrial function in APP/PS1 mice. The data suggest that rapamycin effectively alleviates AD-like behaviors and synaptic plasticity deficits in APP/PS1 mice, which is associated with enhanced mitophagy. Our findings possibly uncover an important function of mitophagy in eliminating damaged mitochondria to attenuate Alzheimer’s disease-associated pathology.

Previous studies have demonstrated the immunomodulatory functions of mesenchymal stem cells (MSCs) in cerebral ischemic rats. However, the underlying mechanisms are unclear. The purpose of this study is to investigate the effects of MSC transplantation on transcriptional regulations of proinflammatory genes in cerebral ischemia. Transient ischemia was induced by middle cerebral artery occlusion (MCAO) in adult male Sprague-Dawley rats. After 24 hr, vehicle (PBS) or a human MSC line (B10) was transplanted intravenously. The neurological deficits, infarct volume, cellular accumulations, and gene expression changes were monitored by means of behavior tests, MRI, immunohistochemistry, Western blotting, laser capture microdissection, and real-time PCR. In the core area of the B10 transplantation group, the number of ED1-positive macrophage/microglia was decreased compared with the PBS group. In the core, nuclear factor-κB (NF-κB) was decreased, although CCAAT/enhancer-binding protein β was not changed; both were expressed mainly in ED1-positive macrophage/microglia. Likewise, mRNAs of NF-κB-dependent genes including interleukin-1β, MCP-1, and inducible nitric oxide synthase were decreased in ED1-positive and Iba-1-positive macrophage/microglia in the B10 transplantation group. Moreover, upstream receptors of the NF-κB pathway, including CD40 and Toll-like receptor 2 (TLR2), were decreased. Immunofluorescence results showed that, in the B10 transplantation group, the percentages of NF-κB-positive, CD40-positive, and TLR2-positive cells were decreased in ED1-positive macrophage/microglia. Furthermore, NF-κB-positive cells in the CD40- or TLR2-expressing cell population were decreased in the B10 transplantation group. This study demonstrates that B10 transplantation inhibits NF-κB activation, possibly through inhibition of CD40 and TLR2, which might be responsible for the inhibition of proinflammatory gene expression in macrophage/microglia in the infarct lesion.

In adult mammalian brain, vascular cells reside throughout life, close to central nervous system germinal zones, and neural stem cells (NSCs) mainly localize in the dentate gyrus of the hippocampus, subventricular zone, and olfactory bulb. Microvessels appear to produce a special microenvironment that may influence the characteristics of NSCs. To explore this potential correlation, an in vitro model with cocultured cerebral microvascular endothelial cells (CMECs) and NSCs was established in our study by using a transwell coculture system.

How time is measured by neural stem cells during temporal neurogenesis has remained unresolved. By combining experiments and computational modeling, we define a Shh/Gli-driven three-node timer underlying the sequential generation of motor neurons (MNs) and serotonergic neurons in the brainstem. The timer is founded on temporal decline of Gli-activator and Gli-repressor activities established through down-regulation of Gli transcription. The circuitry conforms an incoherent feed-forward loop, whereby Gli proteins not only promote expression of Phox2b and thereby MN-fate but also account for a delayed activation of a self-promoting transforming growth factor–β (Tgfβ) node triggering a fate switch by repressing Phox2b. Hysteresis and spatial averaging by diffusion of Tgfβ counteract noise and increase temporal accuracy at the population level, providing a functional rationale for the intrinsically programmed activation of extrinsic switch signals in temporal patterning. Our study defines how time is reliably encoded during the sequential specification of neurons.