Golden Exosomes Selectively Target Brain Pathologies in Neurodegenerative and Neurodevelopmental Disorders.

Exosomes, nanovesicles that are secreted by different cell types, enable intercellular communication at local or distant sites. Alhough they have been found to cross the blood brain barrier, their migration and homing abilities within the brain remain unstudied. We have recently developed a method for longitudinal and quantitative in vivo neuroimaging of exosomes based on the superior visualization abilities of classical X-ray computed tomography (CT), combined with gold nanoparticles as labeling agents. Here, we used this technique to track the migration and homing patterns of intranasally administrated exosomes derived from bone marrow mesenchymal stem cells (MSC-exo) in different brain pathologies, including stroke, autism, Parkinson's disease, and Alzheimer's disease. We found that MSC-exo specifically targeted and accumulated in pathologically relevant murine models brains regions up to 96 h post administration, while in healthy controls they showed a diffuse migration pattern and clearance by 24 h. The neuro-inflammatory signal in pathological brains was highly correlated with MSC-exo accumulation, suggesting that the homing mechanism is inflammatory-driven. In addition, MSC-exo were selectively uptaken by neuronal cells, but not glial cells, in the pathological regions. Taken together, these findings can significantly promote the application of exosomes for therapy and targeted drug delivery in various brain pathologies.

Toll-Like Receptor-4 Inhibitor TAK-242 Attenuates Motor Dysfunction and Spinal Cord Pathology in an Amyotrophic Lateral Sclerosis Mouse Model.

Neuroinflammation contributes to amyotrophic lateral sclerosis (ALS) progression. TLR4, a transmembrane protein that plays a central role in activation of the innate immune system, has been shown to induce microglial activation in ALS models. TLR4 is up-regulated in the spinal cords of hSOD1G93A mice. We aimed to examine the effects of specific TLR4 inhibition on disease progression and survival in the hSOD1G93A mouse model of ALS. Immunologic effect of TLR4 inhibition in vitro was measured by the effect of TAK-242 treatment on LPS-induced splenocytes proliferation. hSOD1G93A transgenic mice were treated with TAK-242, a selective TLR4 inhibitor, or vehicle. Survival, body weight, and motor behavior were monitored. To evaluate in vivo immunologic modifications associated with TAK-242 treatment, we measured serum IL-1ß in the plasma, as well as IL-1ß and TNF-α mRNAs in the spinal cord in wild-type mice and in TAK-242-treated and vehicle-treated early symptomatic hSOD1G93A mice. Immunohistochemical analysis of motor neurons, astrocytes, and microglial reactivity in the spinal cords were performed on symptomatic (100 days old) TAK-242-treated and vehicle-treated hSOD1G93A mice. In vitro, splenocytes taken from 100 days old hSOD1G93A mice showed significantly increased proliferation when exposed to LPS (p = 0.0002), a phenomenon that was reduced by TAK-242 (p = 0.0179). TAK-242 treatment did not attenuate body weight loss or significantly affect survival. However, TAK-242-treated hSOD1G93A mice showed temporary clinical delay in disease progression evident in the ladder test and hindlimb reflex measurements. Plasma IL-1ß levels were significantly reduced in TAK-242-treated compared to vehicle-treated hSOD1G93A mice (p = 0.0023). TAK-242 treatment reduced spinal cord astrogliosis and microglial activation and significantly attenuated spinal cord motor neuron loss at early disease stage (p = 0.0259). Compared to wild-type animals, both IL-1ß and TNF-α mRNAs were significantly upregulated in the spinal cords of hSOD1G93A mice. Spinal cord analysis in TAK-242-treated hSOD1G93A mice revealed significant attenuation of TNF-α mRNA (p = 0.0431), but no change in IL-1ß mRNA. TLR4 inhibition delayed disease progression, attenuated spinal cord astroglial and microglial reaction, and reduced spinal motor neuron loss in the ALS hSOD1G93A mouse model. However, this effect did not result in increased survival. To our knowledge, this is the first report on TAK-242 treatment in a neurodegenerative disease model. Further studies are warranted to assess TLR4 as a therapeutic target in ALS.

Temporal structure of mouse courtship vocalizations facilitates syllable labeling.

Mice emit sequences of ultrasonic vocalizations (USVs) but little is known about the rules governing their temporal order and no consensus exists on the classification of USVs into syllables. To address these questions, we recorded USVs during male-female courtship and found a significant temporal structure. We labeled USVs using three popular algorithms and found that there was no one-to-one relationships between their labels. As label assignment affects the high order temporal structure, we developed the Syntax Information Score (based on information theory) to rank labeling algorithms based on how well they predict the next syllable in a sequence. Finally, we derived a novel algorithm (Syntax Information Maximization) that utilizes sequence statistics to improve the clustering of individual USVs with respect to the underlying sequence structure. Improvement in USV classification is crucial for understanding neural control of vocalization. We demonstrate that USV syntax holds valuable information towards achieving this goal.

Extracellular Vesicles Tracking and Quantification Using CT and Optical Imaging in Rats.

Exosomes, a subtype of extracellular vesicles, are nanovesicles of endocytic origin. Exosomes contain a plethora of proteins, lipids, and genetic materials of parent cells to facilitate intercellular communications. Tracking exosomes in vivo is fundamentally important to understand their biodistribution pattern and the mechanism of biological actions in experimental models. Until now, a number of tracking protocols have been developed, including fluorescence labeling, bioluminescence imaging, magnetic resonance imaging, and computed tomography (CT) tracking of exosomes. Recently, we have shown the tracking and quantification of exosomes in a spinal cord injury model, by using two tracking approaches. More specifically, following intranasal administration of gold nanoparticle-encapsulated exosomes to rats bearing complete spinal cord injury, exosomes in the whole central nervous system were tracked by using microCT, and quantified by using inductively coupled plasma and flame atomic absorption spectroscopy. In addition, optical imaging of fluorescently labeled exosomes was performed to understand the abundance of migrating exosomes in the spinal cord lesion, as compared to the healthy controls, and to further examine their affinity to different cell types in the lesion. Thus, the protocol presented here aids in the study of exosome biodistribution at both cellular and organ levels, in the context of spinal cord injury. This protocol will also enable researchers to better elucidate the fate of administered exosomes in other models of interest.

Correction: Mesenchymal stem cells derived extracellular vesicles improve behavioral and biochemical deficits in a phencyclidine model of schizophrenia.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Mesenchymal stem cells derived extracellular vesicles improve behavioral and biochemical deficits in a phencyclidine model of schizophrenia.

Schizophrenia is a debilitating psychiatric disorder with a significant number of patients not adequately responding to treatment. Phencyclidine (PCP) is used as a validated model for schizophrenia, shown to reliably induce positive, negative and cognitive-like behaviors in rodents. It was previously shown in our lab that behavioral phenotypes of PCP-treated mice can be alleviated after intracranial transplantation of mesenchymal stem cells (MSC). Here, we assessed the feasibility of intranasal delivery of MSCs-derived-extracellular vesicles (EVs) to alleviate schizophrenia-like behaviors in a PCP model of schizophrenia. As MSCs-derived EVs were already shown to concentrate at the site of lesion in the brain, we determined that in PCP induced injury the EVs migrate to the prefrontal cortex (PFC) of treated mice, a most involved area of the brain in schizophrenia. We show that intranasal delivery of MSC-EVs improve social interaction and disruption in prepulse inhibition (PPI) seen in PCP-treated mice. In addition, immunohistochemical studies demonstrate that the EVs preserve the number of parvalbumin-positive GABAergic interneurons in the PFC of treated mice. Finally, MSCs-EVs reduced glutamate levels in the CSF of PCP-treated mice, which might explain the reduction of toxicity. In conclusion, we show that MSCs-EVs improve the core schizophrenia-like behavior and biochemical markers of schizophrenia and might be used as a novel treatment for this incurable disorder.

Correction: Mesenchymal stem cells derived extracellular vesicles improve behavioral and biochemical deficits in a phencyclidine model of schizophrenia.

In the original Article, Dr. Angela Ruban's name was misspelled as "Aangela Ruban". This has been corrected in the PDF, HTML, and XML versions of this Article.

A novel specific PERK activator reduces toxicity and extends survival in Huntington's disease models.

One of the pathways of the unfolded protein response, initiated by PKR-like endoplasmic reticulum kinase (PERK), is key to neuronal homeostasis in neurodegenerative diseases. PERK pathway activation is usually accomplished by inhibiting eIF2α-P dephosphorylation, after its phosphorylation by PERK. Less tried is an approach involving direct PERK activation without compromising long-term recovery of eIF2α function by dephosphorylation. Here we show major improvement in cellular (STHdhQ111/111) and mouse (R6/2) Huntington's disease (HD) models using a potent small molecule PERK activator that we developed, MK-28. MK-28 showed PERK selectivity in vitro on a 391-kinase panel and rescued cells (but not PERK-/- cells) from ER stress-induced apoptosis. Cells were also rescued by the commercial PERK activator CCT020312 but MK-28 was significantly more potent. Computational docking suggested MK-28 interaction with the PERK activation loop. MK-28 exhibited remarkable pharmacokinetic properties and high BBB penetration in mice. Transient subcutaneous delivery of MK-28 significantly improved motor and executive functions and delayed death onset in R6/2 mice, showing no toxicity. Therefore, PERK activation can treat a most aggressive HD model, suggesting a possible approach for HD therapy and worth exploring for other neurodegenerative disorders.

Intranasal Delivery of Mesenchymal Stem Cell Derived Exosomes Loaded with Phosphatase and Tensin Homolog siRNA Repairs Complete Spinal Cord Injury.

Individuals with spinal cord injury (SCI) usually suffer from permanent neurological deficits, while spontaneous recovery and therapeutic efficacy are limited. Here, we demonstrate that when given intranasally, exosomes derived from mesenchymal stem cells (MSC-Exo) could pass the blood brain barrier and migrate to the injured spinal cord area. Furthermore, MSC-Exo loaded with phosphatase and tensin homolog small interfering RNA (ExoPTEN) could attenuate the expression of PTEN in the injured spinal cord region following intranasal administrations. In addition, the loaded MSC-Exo considerably enhanced axonal growth and neovascularization, while reducing microgliosis and astrogliosis. The intranasal ExoPTEN therapy could also partly improve structural and electrophysiological function and, most importantly, significantly elicited functional recovery in rats with complete SCI. The results imply that intranasal ExoPTEN may be used clinically to promote recovery for SCI individuals.

Intranasal administration of exosomes derived from mesenchymal stem cells ameliorates autistic-like behaviors of BTBR mice.

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by three core symptoms that include social interaction deficits, cognitive inflexibility, and communication disorders. They have been steadily increasing in children over the past several years, with no effective treatment. BTBR T+tf/J (BTBR) mice are an accepted model of evaluating autistic-like behaviors as they present all core symptoms of ASD. We have previously shown that transplantation of human bone marrow mesenchymal stem cells (MSC) to the lateral ventricles of BTBR mice results in long lasting improvement in their autistic behavioral phenotypes. Recent studies point exosomes as the main mediators of the therapeutic effect of MSC. Here, we tested whether treatment with the exosomes secreted from MSC (MSC-exo) will show similar beneficial effects. We found that intranasal administration of MSC-exo increased male to male social interaction and reduced repetitive behaviors. Moreover, the treatment led to increases of male to female ultrasonic vocalizations and significant improvement in maternal behaviors of pup retrieval. No negative symptoms were detected following MSC-exo intranasal treatments in BTBR or healthy C57BL mice. The marked beneficial effects of the exosomes in BTBR mice may translate to a novel, non-invasive, and therapeutic strategy to reduce the symptoms of ASD.

In Vivo Neuroimaging of Exosomes Using Gold Nanoparticles.

Exosomes are emerging as effective therapeutic tools for various pathologies. These extracellular vesicles can bypass biological barriers, including the blood-brain barrier, and can serve as powerful drug and gene therapy transporters. However, the progress of therapy development is impeded by several challenges, including insufficient data on exosome trafficking and biodistribution and the difficulty to image deep brain structures in vivo. Herein, we established a method for noninvasive in vivo neuroimaging and tracking of exosomes, based on glucose-coated gold nanoparticle (GNP) labeling and computed tomography imaging. Labeling of exosomes with the GNPs was achieved directly, as opposed to the typical and less efficient indirect labeling mode through parent cells. On the mechanistic level, we found that the glucose-coated GNPs were uptaken into MSC-derived exosomes via an active, energy-dependent mechanism that is mediated by the glucose transporter GLUT-1 and involves endocytic proteins. Next, we determined optimal parameters of size and administration route; we demonstrated that 5 nm GNPs enabled improved exosome labeling and that intranasal, compared to intravenous, administration led to superior brain accumulation and thus enhanced in vivo neuroimaging. Furthermore, using a mouse model of focal brain ischemia, we noninvasively tracked intranasally administered GNP-labeled exosomes, which showed increased accumulation at the lesion site over 24 h, as compared to nonspecific migration and clearance from control brains over the same period. Thus, this exosome labeling technique can serve as a powerful diagnostic tool for various brain disorders and could potentially enhance exosome-based treatments for neuronal recovery.

Long term beneficial effect of neurotrophic factors-secreting mesenchymal stem cells transplantation in the BTBR mouse model of autism.

Autism spectrum disorders (ASD) are neurodevelopmental disabilities characterized by severe impairment in social communication skills and restricted, repetitive behaviors. We have previously shown that a single transplantation of mesenchymal stem cells (MSC) into the cerebral lateral ventricles of BTBR autistic-like mice resulted in an improvement across all diagnostic criteria of ASD. We suggested that brain-derived neurotrophic factor (BDNF), a protein which supports the survival and regeneration of neurons secreted by MSC, largely contributed to the beneficial behavioral effect. In this study, we investigated the behavioral effects of transplanted MSC induced to secrete higher amounts of neurotrophic factors (NurOwn®), on various ASD-related behavioral domains using the BTBR mouse model of ASD. We demonstrate that NurOwn® transplantation had significant advantages over MSC transplantation in terms of improving communication skills, one and six months following treatment, as compared to sham-treated BTBR mice. Furthermore, NurOwn® transplantation resulted in reduced stereotypic behavior for as long as six months post treatment, compared to the one month improvement observed in the MSC treated mice. Notably, NurOwn® treatment resulted in improved cognitive flexibility, an improvement that was not observed by MSC treatment. Both MSC and NurOwn® transplantation induced an improvement in social behavior that lasted for six months. In conclusion, the present study demonstrates that a single transplantation of MSC or NurOwn® have long-lasting benefits, while NurOwn® may be superior to MSC treatment.

Social Ultrasonic Vocalization in Awake Head-Restrained Mouse.

Numerous animal species emit vocalizations in response to various social stimuli. The neural basis of vocal communication has been investigated in monkeys, songbirds, rats, bats, and invertebrates resulting in deep insights into motor control, neural coding, and learning. Mice, which recently became very popular as a model system for mammalian neuroscience, also utilize ultrasonic vocalizations (USVs) during mating behavior. However, our knowledge is lacking of both the behavior and its underlying neural mechanism. We developed a novel method for head-restrained male mice (HRMM) to interact with non-restrained female mice (NRFM) and show that mice can emit USVs in this context. We first recorded USVs in a free arena with non-restrained male mice (NRMM) and NRFM. Of the NRMM, which vocalized in the free arena, the majority could be habituated to also vocalize while head-restrained but only when a female mouse was present in proximity. The USVs emitted by HRMM are similar to the USVs of NRMM in the presence of a female mouse in their spectral structure, inter-syllable interval distribution, and USV sequence length, and therefore are interpreted as social USVs. By analyzing the vocalizations of NRMM, we established criteria to predict which individuals are likely to vocalize while head fixed based on the USV rate and average syllable duration. To characterize the USVs emitted by HRMM, we analyzed the syllable composition of HRMM and NRMM and found that USVs emitted by HRMM have a higher proportion of USVs with complex spectral representation, supporting previous studies showing that mice social USVs are context dependent. Our results suggest a way to study the neural mechanisms of production and control of social vocalization in mice using advanced methods requiring head fixation.