Simple and Highly Specific Targeting of Resident Microglia with Adeno-Associated Virus.

Microglia, as the immune cells of the central nervous system (CNS), play dynamic roles in both health and diseased conditions. The ability to genetically target microglia using viruses is crucial for understanding their functions and advancing microglia-based treatments. We here show that resident microglia can be simply and specifically targeted using adeno-associated virus (AAV) vectors containing a 466-bp DNA fragment from the human IBA1 (hIBA1) promoter. This targeting approach is applicable to both resting and reactive microglia. When combining the short hIBA1 promoter with the target sequence of miR124, up to 95% of transduced cells are identified as microglia. Such a simple and highly specific microglia-targeting strategy may be further optimized for research and therapeutics.

A single factor elicits multilineage reprogramming of astrocytes in the adult mouse striatum.

SignificanceOutside the neurogenic niches, the adult brain lacks multipotent progenitor cells. In this study, we performed a series of in vivo screens and reveal that a single factor can induce resident brain astrocytes to become induced neural progenitor cells (iNPCs), which then generate neurons, astrocytes, and oligodendrocytes. Such a conclusion is supported by single-cell RNA sequencing and multiple lineage-tracing experiments. Our discovery of iNPCs is fundamentally important for regenerative medicine since neural injuries or degeneration often lead to loss/dysfunction of all three neural lineages. Our findings also provide insights into cell plasticity in the adult mammalian brain, which has largely lost the regenerative capacity.

Human placental mesenchymal stem cells improve stroke outcomes via extracellular vesicles-mediated preservation of cerebral blood flow.

BACKGROUND: Besides long-term trans-differentiation into neural cells, benefits of stem cell therapy (SCT) in ischemic stroke may include secretion of protective factors, which partly reflects extracellular vesicle (EVs) released by stem cell. However, the mechanism(s) by which stem cells/EVs limit stroke injury have yet to be fully defined. METHODS: We evaluated the protection effect of human placenta mesenchymal stem cells (hPMSC) as a potential form of SCT in experimental ischemic stroke 'transient middle cerebral artery occusion (MCAO)/reperfusion' mice model. FINDINGS: We found for the first time that intraperitoneal administration of hPMSCs or intravenous hPMSC-derived EVs, given at the time of reperfusion, significantly protected the ipsilateral hemisphere from ischemic injury. This protection was associated with significant restoration of normal blood flow to the post-MCAO brain. More importantly, EVs derived from hPMSC promote paracrine-based protection of SCT in the MCAO model in a cholesterol/lipid-dependent manner. INTERPRETATION: Together, our results demonstrated beneficial effects of hPMSC/EVs in experimental stroke models which could permit the rapid "translation" of these cells into clinical trials in the near-term.

Obstructive sleep apnea intensifies stroke severity following middle cerebral artery occlusion.

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) is a sleep disorder caused by transient obstruction of the upper airway and results in intermittent hypoxia, sleep fragmentation, sympathetic nervous system activation, and arousal which can have an adverse effect on cardiovascular disease. It is theorized that OSA might intensify stroke injury. Our goal here was to develop a new model of experimental OSA and test its ability to aggravate behavioral and morphological outcomes following transient brain ischemia/reperfusion. METHODS: We used a 3D printed OSA device to expose C57BL6 mice to 3 h of OSA (obstructive apnea index of 20 events per hour) for three days. These mice were then subjected to ischemia/reperfusion using the middle cerebral artery occlusion model (MCAO) stroke and examined for overall survival, infarct size and neurological scoring. RESULTS: We found that OSA transiently decreased respiration and reduced oxygen saturation with bradycardia and tachycardia typical of human responses during apneic events. Brain injury from MCAO was significantly increased by OSA as measured by infarct size and location as well as by intensification of neurological deficits; mortality following MCAO was also increased in OSA animals. CONCLUSIONS: Our findings suggest that our new model of OSA alters respiratory and cardiovascular physiological functions and is associated with enhanced ischemia/reperfusion mediated injury in our non-invasive, OSA intensified model of stroke.

In Utero Exposure to Alcohol Impairs Reactivity of Cerebral Arterioles and Increases Susceptibility of the Brain to Damage Following Ischemia/Reperfusion in Adulthood.

BACKGROUND: Maternal consumption of alcohol produces abnormalities in the developing fetus and can contribute to an increased incidence of many cardiovascular-related diseases. The first goal of this study was to determine whether in utero exposure to alcohol influences reactivity of cerebral arterioles in adult (12 to 15 weeks old) rats. The second goal of this study was to examine whether in utero exposure to alcohol increased the susceptibility of the brain to damage following an ischemic event in adult rats. METHODS: We fed Sprague Dawley dams a liquid diet with or without alcohol (3% ethanol) for the duration of their pregnancy (21 to 23 days). In the first series of studies, we examined reactivity of cerebral arterioles to endothelial nitric oxide synthase (eNOS)- (adenosine diphosphate [ADP]) and neuronal nitric oxide synthase (nNOS)-dependent N-methyl-D-aspartate (NMDA, and NOS-independent agonists in adult rats before and during application of l-NMMA. In another series of studies, we examined infarct volume following middle cerebral artery occlusion in adult offspring exposed to alcohol in utero. In both series of studies, we also determined the role for an increase in oxidative stress by feeding dams apocynin for the duration of their pregnancy. RESULTS: We found that in utero exposure to alcohol reduced responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in adult rats. In addition, treatment of the dams with apocynin prevented this impairment in cerebral vascular function. We also found that in utero exposure to alcohol worsened brain damage following ischemia/reperfusion in adult rats and that treatment of dams with apocynin prevented this increase in brain damage following ischemia/reperfusion. CONCLUSIONS: We suggest that our findings may have important implications for the pathogenesis of brain abnormalities associated with fetal alcohol exposure.

In utero exposure to alcohol alters reactivity of cerebral arterioles.

Our goal was to examine whether in utero exposure to alcohol impaired reactivity of cerebral arterioles during development. We fed Sprague-Dawley dams a liquid diet with or without alcohol (3% ethanol) for the duration of pregnancy (21-23 days). Around 4-6 weeks after birth, we examined reactivity of cerebral arterioles to eNOS- (ADP) and nNOS-dependent (NMDA) agonists in the offspring. We found that in utero exposure to alcohol attenuated responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in rats exposed to alcohol in utero. L-NMMA reduced responses to agonists in control rats, but not in rats exposed to alcohol in utero. Treatment of dams with apocynin for the duration of pregnancy rescued the impairment in reactivity to ADP and NMDA in the offspring. Protein expression of NOX-2 and NOX-4 was increased in alcohol rats compared to control rats. We also found an increase in superoxide levels in the cortex of rats exposed to alcohol in utero. Our findings suggest that in utero exposure to alcohol impairs eNOS and nNOS reactivity of cerebral arterioles via a chronic increase in oxidative stress.

Severe respiratory changes at end stage in a FUS-induced disease state in adult rats.

BACKGROUND: Fused in sarcoma (FUS) is an RNA-binding protein associated with the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration. ALS manifests in patients as a progressive paralysis which leads to respiratory dysfunction and failure, the primary cause of death in ALS. We expressed human FUS in rats to determine if FUS would induce ALS relevant respiratory changes to serve as an early stage disease indicator. The FUS expression was initiated in adult rats by way of an intravenously administered adeno-associated virus vector serotype 9 (AAV9) providing an adult onset model. RESULTS: The rats developed progressive motor impairments observed as early as 2-3 weeks post gene transfer. Respiratory abnormalities manifested 4-7 weeks post gene transfer including increased respiratory frequency and decreased tidal volume. Rats with breathing abnormalities also had arterial blood acidosis. Similar detailed plethysmographic changes were found in adult rats injected with AAV9 TDP-43. FUS gene transfer to adult rats yielded a consistent pre-clinical model with relevant motor paralysis in the early to middle stages and respiratory dysfunction at the end stage. Both FUS and TDP-43 yielded a similar consistent disease state. CONCLUSIONS: This modeling method yields disease relevant motor and respiratory changes in adult rats. The reproducibility of the data supports the use of this method to study other disease related genes and their combinations as well as a platform for disease modifying interventional strategies.

Vigorous exercise training improves reactivity of cerebral arterioles and reduces brain injury following transient focal ischemia.

OBJECTIVE: Our objective was to examine whether vigorous exercise training (VExT) could influence nitric oxide synthase (NOS)-dependent vasodilation and transient focal ischemia-induced brain injury. Rats were divided into sedentary (SED) or VExT groups. MATERIALS AND METHODS: Exercise was carried out 5 days/week for a period of 8-10 weeks. First, we measured responses of pial arterioles to an eNOS-dependent (ADP), an nNOS-dependent (NMDA) and a NOS-independent (nitroglycerin) agonist in SED and VExT rats. Second, we measured infarct volume in SED and VExT rats following middle cerebral artery occlusion (MCAO). Third, we measured superoxide levels in brain tissue of SED and VExT rats under basal and stimulated conditions. RESULTS: We found that eNOS- and nNOS-dependent, but not NOS-independent vasodilation, was increased in VExT compared to SED rats, and this could be inhibited with L-NMMA in both groups. In addition, we found that VExT reduced infarct volume following MCAO when compared to SED rats. Further, superoxide levels were similar in brain tissue from SED and VExT rats under basal and stimulated conditions. CONCLUSIONS: We suggest that VExT potentiates NOS-dependent vascular reactivity and reduces infarct volume following MCAO via a mechanism that appears to be independent of oxidative stress, but presumably related to an increase in the contribution of nitric oxide.