The Association between Glymphatic System and Perivascular Macrophages in Brain Waste Clearance.

The glymphatic system suggests the convective bulk flow of cerebrospinal fluid (CSF) through perivascular spaces and the interstitial spaces of the brain parenchyma for the rapid removal of toxic waste solutes from the brain. However, the presence of convective bulk flow within the brain interstitial spaces is still under debate. We first addressed this argument to determine the involvement of the glymphatic system in brain waste clearance utilizing contrast-enhanced 3D T1-weighted imaging (T1WI), diffusion tensor imaging (DTI), and confocal microscopy imaging. Furthermore, perivascular macrophages (PVMs), which are immune cells located within perivascular spaces, have not been thoroughly explored for their association with the glymphatic system. Therefore, we investigated tracer uptake by PVMs in the perivascular spaces of both the arteries/arterioles and veins/venules and the potential association of PVMs in assisting the glymphatic system for interstitial waste clearance. Our findings demonstrated that both convective bulk flow and diffusion are responsible for the clearance of interstitial waste solutes from the brain parenchyma. Furthermore, our results suggested that PVMs may play an important function in glymphatic system-mediated interstitial waste clearance. The glymphatic system and PVMs could be targeted to enhance interstitial waste clearance in patients with waste-associated neurological conditions and aging.

The Glymphatic Response to the Development of Type 2 Diabetes.

The glymphatic system has recently been shown to be important in neurological diseases, including diabetes. However, little is known about how the progressive onset of diabetes affects the glymphatic system. The aim of this study is to investigate the glymphatic system response to the progressive onset of diabetes in a rat model of type 2 diabetic mellitus. Male Wistar rats (n = 45) with and without diabetes were evaluated using MRI glymphatic tracer kinetics, functional tests, and brain tissue immunohistochemistry. Our data demonstrated that the contrast agent clearance impairment gradually progressed with the diabetic duration. The MRI data showed that an impairment in contrast clearance occurred prior to the cognitive deficits detected using functional tests and permitted the detection of an early DM stage compared to the immuno-histopathology and cognitive tests. Additionally, the quantitative MRI markers of brain waste clearance demonstrated region-dependent sensitivity in glymphatic impairment. The improved sensitivity of MRI markers in the olfactory bulb and the whole brain at an early DM stage may be attributed to the important role of the olfactory bulb in the parenchymal efflux pathway. MRI can provide sensitive quantitative markers of glymphatic impairment during the progression of DM and can be used as a valuable tool for the early diagnosis of DM with a potential for clinical application.

Adipose-derived exosomal miR-421 targets CBX7 and promotes metastatic potential in ovarian cancer cells.

BACKGROUND: Chromobox protein homolog 7 (CBX7), a member of the Polycomb repressor complex, is a potent epigenetic regulator and gene silencer. Our group has previously reported that CBX7 functions as a tumor suppressor in ovarian cancer cells and its loss accelerated formation of carcinomatosis and drove tumor progression in an ovarian cancer mouse model. The goal of this study is to identify specific signaling pathways in the ovarian tumor microenvironment that down-regulate CBX7. Given that adipocytes are an integral component of the peritoneal cavity and the ovarian tumor microenvironment, we hypothesize that the adipose microenvironment is an important regulator of CBX7 expression. RESULTS: Using conditioned media from human omental explants, we found that adipose-derived exosomes mediate CBX7 downregulation and enhance migratory potential of human ovarian cancer cells. Further, we identified adipose-derived exosomal miR-421 as a novel regulator of CBX7 expression and the main effector that downregulates CBX7. CONCLUSION: In this study, we identified miR-421 as a specific signaling pathway in the ovarian tumor microenvironment that can downregulate CBX7 to induce epigenetic change in OC cells, which can drive disease progression. These findings suggest that targeting exosomal miR-421 may curtail ovarian cancer progression.

Adipose-derived exosomal miR-421 targets CBX7 and promotes metastatic potential in ovarian cancer cells.

Background: Chromobox protein homolog 7 (CBX7), a member of the Polycomb repressor complex, is a potent epigenetic regulator and gene silencer. Our group has previously reported that CBX7 functions as a tumor suppressor in ovarian cancer cells and its loss accelerated formation of carcinomatosis and drove tumor progression in an ovarian cancer mouse model. The goal of this study is to identify specific signaling pathways in the ovarian tumor microenvironment that down-regulate CBX7. Given that adipocytes are an integral component of the peritoneal cavity and the ovarian tumor microenvironment, we hypothesize that the adipose microenvironment is an important regulator of CBX7 expression. Results: Using conditioned media from human omental explants, we found that adipose-derived exosomes mediate CBX7 downregulation and enhance migratory potential of human ovarian cancer cells. Further, we identified adipose-derived exosomal miR-421 as a novel regulator of CBX7 expression and the main effector that downregulates CBX7. Conclusion: In this study, we identified miR-421 as a specific signaling pathway in the ovarian tumor microenvironment that can downregulate CBX7 to induce epigenetic change in OC cells, which can drive disease progression. These findings suggest that targeting exosomal miR-421 may curtail ovarian cancer progression.

Imaging glymphatic response to glioblastoma.

BACKGROUND: The glymphatic system actively exchanges cerebrospinal fluid (CSF) and interstitial fluid (ISF) to eliminate toxic interstitial waste solutes from the brain parenchyma. Impairment of the glymphatic system has been linked to several neurological conditions. Glioblastoma, also known as Glioblastoma multiforme (GBM) is a highly aggressive form of malignant brain cancer within the glioma category. However, the impact of GBM on the functioning of the glymphatic system has not been investigated. Using dynamic contrast-enhanced magnetic resonance imaging (CE-MRI) and advanced kinetic modeling, we examined the changes in the glymphatic system in rats with GBM. METHODS: Dynamic 3D contrast-enhanced T1-weighted imaging (T1WI) with intra-cisterna magna (ICM) infusion of paramagnetic Gd-DTPA contrast agent was used for MRI glymphatic measurements in both GBM-induced and control rats. Glymphatic flow in the whole brain and the olfactory bulb was analyzed using model-derived parameters of arrival time, infusion rate, clearance rate, and residual that describe the dynamics of CSF tracer over time. RESULTS: 3D dynamic T1WI data identified reduced glymphatic influx and clearance, indicating an impaired glymphatic system due to GBM. Kinetic modeling and quantitative analyses consistently indicated significantly reduced infusion rate, clearance rate, and increased residual of CSF tracer in GBM rats compared to control rats, suggesting restricted glymphatic flow in the brain with GBM. In addition, our results identified compromised perineural pathway along the optic nerves in GBM rats. CONCLUSIONS: Our study demonstrates the presence of GBM-impaired glymphatic response in the rat brain and impaired perineural pathway along the optic nerves. Reduced glymphatic waste clearance may lead to the accumulation of toxic waste solutes and pro-inflammatory signaling molecules which may affect the progression of the GBM.

The Association between Glymphatic System and Perivascular Macrophages in Brain Waste Clearance.

The glymphatic system suggests the convective bulk flow of cerebrospinal fluid (CSF) through perivascular spaces and the interstitial spaces of the brain parenchyma for the rapid removal of toxic waste solutes from the brain. However, the presence of convective bulk flow within the brain interstitial spaces is still under debate. We first addressed this argument to determine the involvement of the glymphatic system in brain waste clearance utilizing contrast-enhanced 3D T1-weighted imaging (T1WI), diffusion tensor imaging (DTI), and confocal microscopy imaging. Furthermore, perivascular macrophages (PVMs), which are immune cells located within perivascular spaces, have not been thoroughly explored for their association with the glymphatic system. Therefore, we investigated tracer uptake by PVMs in the perivascular spaces of both the arteries/arterioles and veins/venules and the potential association of PVMs in assisting the glymphatic system for interstitial waste clearance. Our findings demonstrated that both convective bulk flow and diffusion are responsible for the clearance of interstitial waste solutes from the brain parenchyma. Furthermore, our results suggested that PVMs play an important function in glymphatic system-mediated interstitial waste clearance. The glymphatic system and PVMs could be targeted to enhance interstitial waste clearance in patients with waste-associated neurological conditions and aging.

Therapeutic effects of CD133 + Exosomes on liver function after stroke in type 2 diabetic mice.

Background and purpose: Non-alcoholic fatty liver disease (NAFLD) is known to adversely affect stroke recovery. However, few studies investigate how stroke elicits liver dysfunction, particularly, how stroke in type 2 diabetes mellitus (T2DM) exacerbates progression of NAFLD. In this study, we test whether exosomes harvested from human umbilical cord blood (HUCBC) derived CD133 + cells (CD133 + Exo) improves neuro-cognitive outcome as well as reduces liver dysfunction in T2DM female mice. Methods: Female, adult non-DM and T2DM mice subjected to stroke presence or absence were considered. T2DM-stroke mice were randomly assigned to receive PBS or Exosome treatment group. CD133 + Exo (20 µg/200 µl PBS, i.v.) was administered once at 3 days after stroke. Evaluation of neurological (mNSS, adhesive removal test) and cognitive function [novel object recognition (NOR) test, odor test] was performed. Mice were sacrificed at 28 days after stroke and brain, liver, and serum were harvested. Results: Stroke induces severe and significant short-term and long-term neurological and cognitive deficits which were worse in T2DM mice compared to non-DM mice. CD133 + Exo treatment of T2DM-stroke mice significantly improved neurological function and cognitive outcome indicated by improved discrimination index in the NOR and odor tests compared to control T2DM-stroke mice. CD133 + Exo treatment of T2DM stroke significantly increased vascular and white matter/axon remodeling in the ischemic brain compared to T2DM-stroke mice. However, there were no differences in the lesion volume between non-DM stroke, T2DM-stroke and CD133 + Exo treated T2DM-stroke mice. In T2DM mice, stroke induced earlier and higher TLR4, NLRP3, and cytokine expression (SAA, IL1ß, IL6, TNFα) in the liver compared to heart and kidney, as measured by Western blot. T2DM-stroke mice exhibited worse NAFLD progression with increased liver steatosis, hepatocellular ballooning, fibrosis, serum ALT activity, and higher NAFLD Activity Score compared to T2DM mice and non-DM-stroke mice, while CD133 + Exo treatment significantly attenuated the progression of NAFLD in T2DM stroke mice. Conclusion: Treatment of female T2DM-stroke mice with CD133 + Exo significantly reduces the progression of NAFLD/NASH and improves neurological and cognitive function compared to control T2DM-stroke mice.

Insight into the Contact Impedance between the Electrode and the Skin Surface for Electrophysical Recordings.

To obtain a performance improved dry electrode for bioelectrical activity detection is still a challenge, which is mainly due to the poor fundamental understanding on the impedance of the electrode-skin interface. Herein, the impedance between the electrode and the skin interface of three types of electrodes, which are the wet electrode, semidry electrode, and dry electrode, is investigated with electrochemical impedance spectroscopy combined with the spectra fitting technique. The parameters of performance duration, potential, and frequency associated with the impedance are explored for these three types of electrodes. The overall impedance is roughly constant within the performance duration and the potential applied in this study. Along with the frequency decreases, the impedance of the dry electrode reduces faster and is more complicated compared with the other two types of electrodes. Moreover, the results computed with the equivalent circuits show that the charge transfer resistance is additionally present compared to the wet and semidry electrodes. This large and additional charge transfer resistance may explain its relatively poorer electrophysiological properties.

MRI Metrics of Cerebral Endothelial Cell-Derived Exosomes for the Treatment of Cognitive Dysfunction Induced in Aging Rats Subjected to Type 2 Diabetes.

Ongoing neurovascular dysfunction contributes to type 2 diabetes mellitus (T2DM)-induced cognitive deficits. However, it is not known whether early post onset of T2DM interventions may reduce evolving neurovascular dysfunction and thereby lead to diminution of T2DM-induced cognitive deficits. Using multiple MRI metrics, we evaluated neurovascular changes in T2DM rats treated with exosomes derived from cerebral endothelial cells (CEC-Exos). Two months after induction of T2DM in middle-aged male rats by administration of streptozotocin nicotinamide, rats were randomly treated with CEC-Exos twice weekly or saline for 4 consecutive weeks (n = 10/group). MRI measurements were performed at the end of the treatment, which included cerebral blood flow (CBF), contrast-enhanced T1-weighted imaging, and relaxation time constants T1 and T2. MRI analysis showed that compared with controls, the CEC-Exo-treated T2DM rats exhibited significant elevation of T2 and CBF in white matter and significant augmentation of T1 and reduction of blood-brain barrier permeability in gray matter. In the hippocampus, CEC-Exo treatment significantly increased T1 and CBF. Furthermore, CEC-Exo treatment significantly reduced T2DM-induced cognitive deficits measured by the Morris water maze and odor recognition tests. Collectively, our corresponding MRI data demonstrate that treatment of T2DM rats with CEC-Exos robustly reduced neurovascular dysfunction in gray and white matter and the hippocampus.

Waste Clearance in the Brain.

Waste clearance (WC) is an essential process for brain homeostasis, which is required for the proper and healthy functioning of all cerebrovascular and parenchymal brain cells. This review features our current understanding of brain WC, both within and external to the brain parenchyma. We describe the interplay of the blood-brain barrier (BBB), interstitial fluid (ISF), and perivascular spaces within the brain parenchyma for brain WC directly into the blood and/or cerebrospinal fluid (CSF). We also discuss the relevant role of the CSF and its exit routes in mediating WC. Recent discoveries of the glymphatic system and meningeal lymphatic vessels, and their relevance to brain WC are highlighted. Controversies related to brain WC research and potential future directions are presented.

Connectivity characterization of the mouse basolateral amygdalar complex.

The basolateral amygdalar complex (BLA) is implicated in behaviors ranging from fear acquisition to addiction. Optogenetic methods have enabled the association of circuit-specific functions to uniquely connected BLA cell types. Thus, a systematic and detailed connectivity profile of BLA projection neurons to inform granular, cell type-specific interrogations is warranted. Here, we apply machine-learning based computational and informatics analysis techniques to the results of circuit-tracing experiments to create a foundational, comprehensive BLA connectivity map. The analyses identify three distinct domains within the anterior BLA (BLAa) that house target-specific projection neurons with distinguishable morphological features. We identify brain-wide targets of projection neurons in the three BLAa domains, as well as in the posterior BLA, ventral BLA, posterior basomedial, and lateral amygdalar nuclei. Inputs to each nucleus also are identified via retrograde tracing. The data suggests that connectionally unique, domain-specific BLAa neurons are associated with distinct behavior networks.

Allograft or Recipient ST2 Deficiency Oppositely Affected Cardiac Allograft Vasculopathy via Differentially Altering Immune Cells Infiltration.

The role of IL-33/ST2 signaling in cardiac allograft vasculopathy (CAV) is not fully addressed. Here, we investigated the role of IL-33/ST2 signaling in allograft or recipient in CAV respectively using MHC-mismatch murine chronic cardiac allograft rejection model. We found that recipients ST2 deficiency significantly exacerbated allograft vascular occlusion and fibrosis, accompanied by increased F4/80+ macrophages and CD3+ T cells infiltration in allografts. In contrast, allografts ST2 deficiency resulted in decreased infiltration of F4/80+ macrophages, CD3+ T cells and CD20+ B cells and thus alleviated vascular occlusion and fibrosis of allografts. These findings indicated that allografts or recipients ST2 deficiency oppositely affected cardiac allograft vasculopathy/fibrosis via differentially altering immune cells infiltration, which suggest that interrupting IL-33/ST2 signaling locally or systematically after heart transplantation leads different outcome.

Single Versus Multi-channel Dispersion Analysis of Ultrasonic Guided Waves Propagating in Long Bones.

Ultrasonic guided wave techniques have been applied to characterize cortical bone for osteoporosis assessment. Compared with the current gold-standard X-ray-based diagnostic methods, ultrasound-based techniques pose some advantages such as compactness, low cost, lack of ionizing radiation, and their ability to detect the mechanical properties of the cortex. Axial transmission technique with a source-receiver offset is employed to acquire the ultrasound data. The dispersion characteristics of the guided waves in bones are normally analyzed in the transformed domains using the dispersion curves. The transformed domain can be time-frequency map using a single channel or wavenumber-frequency (or phase velocity-frequency) map with multi-channels. In terms of acquisition effort, the first method is more cost- and time-effective than the latter. However, it remains unclear whether single-channel dispersion analysis can provide as much quantitative guided-wave information as the multi-channel analysis. The objective of this study is to compare the two methods using numerically simulated and ex vivo data of a simple bovine bone plate and explore their advantages and disadvantages. Both single- and multi-channel signal processing approaches are implemented using sparsity-constrained optimization algorithms to reinforce the focusing power. While the single-channel data acquisition and processing are much faster than those of the multi-channel, modal identification and analysis of the multi-channel data are straightforward and more convincing.

Epigenetic Mechanisms Underlying Adult Post Stroke Neurogenesis.

Stroke remains the leading cause of adult disability. Post-stroke neurogenesis contributes to functional recovery. As an intrinsic neurorestorative process, it is important to elucidate the molecular mechanism underlying stroke-induced neurogenesis and to develop therapies designed specifically to augment neurogenesis. Epigenetic mechanisms include DNA methylation, histone modification and its mediation by microRNAs and long-non-coding RNAs. In this review, we highlight how epigenetic factors including DNA methylation, histone modification, microRNAs and long-non-coding RNAs mediate stroke-induced neurogenesis including neural stem cell self-renewal and cell fate determination. We also summarize therapies targeting these mechanisms in the treatment of stroke.

Transplantable Carbonaceous Li+ Filtrating Membrane for Lithium Metal Protection.

Utilization of the lithium (Li) metal anode is seriously prevented by the undesirable side reactions with electrolyte solvents due to their mismatched energy gaps and easily lacerated SEI layer. In this work, we develop a transplantable carbonaceous membrane with a particular ability of filtrating Li+ ions by blocking organic solvents and use it as an independent protective component to isolate lithium metal anode from the electrolytes. This graphene-supported N-doped membrane (GNM) can separate organic carbonates of dimethyl carbonate (DMC) and diethyl carbonate (DEC) from H2O-DMC/DEC mixtures by holding back the organic solvents. When this membrane is used in a Li-Cu cell, a high Li Coulombic efficiency (CE) of 98.5% is maintained in carbonate electrolyte over 400 cycles. Application of GNM in Li-O2 full cell provides a sustainable use of Li metal for more than 200 cycles (2000 h) by keeping its shiny metal luster. Our results demonstrate that the use of an independent component with Li+ filtrating ability, such as the transplantable membrane of GNM developed in this work, should be a feasible remedy to protect Li metal anode in practical Li metal batteries.

Magnetic Resonance Imaging and Modeling of the Glymphatic System.

The glymphatic system is a newly discovered waste drainage pathway in the brain; it plays an important role in many neurological diseases. Ongoing research utilizing various cerebrospinal fluid tracer infusions, either directly or indirectly into the brain parenchyma, is investigating clearance pathways by using distinct imaging techniques. In the present review, we discuss the role of the glymphatic system in various neurological diseases and efflux pathways of brain waste clearance based on current evidence and controversies. We mainly focus on new magnetic resonance imaging (MRI) modeling techniques, along with traditional computational modeling, for a better understanding of the glymphatic system function. Future sophisticated modeling techniques hold the potential to generate quantitative maps for glymphatic system parameters that could contribute to the diagnosis, monitoring, and prognosis of neurological diseases. The non-invasive nature of MRI may provide a safe and effective way to translate glymphatic system measurements from bench-to-bedside.

Differences between normal and diabetic brains in middle-aged rats by MRI.

Normal aging is a risk factor for metabolic disorders such as diabetes, and diabetes is also a recognized cause of accelerated aging. Being able to distinguish changes caused by normal aging from those caused by diabetes, would provide insight into how the aging brain interacts with diabetes. Eight types of MRI metric maps (magnetization relaxation time constants of T1 and T2, cerebral blood flow, cerebrovascular permeability, mean diffusivity, diffusion fractional anisotropy, mean diffusion kurtosis and diffusion directional entropy) were generated for all rats from the three groups of normal young, healthy and 1.5-month diabetic middle-aged rats under investigation. Measurements of multiple MRI indices of cerebral white and gray matter from animals of the three groups provide complementary results and insight into differences between healthy and diabetic white / gray matter in the mid-aged rats. Our data indicate that MRI may distinguish between the normal and diabetes in mid-aged rat brains by measuring either T1 and T2 of gray matter, or fractional anisotropy of white matter and gray matter. Therefore, MRI can distinguish changes of cerebral tissue due to the normal aging from diabetic aging, which may lead to be able to better understand how diabetes accelerates aging in normal brain.

Role of the glymphatic system in ageing and diabetes mellitus impaired cognitive function.

Diabetes mellitus (DM) is a common metabolic disease in the middle-aged and older population, and is associated with cognitive impairment and an increased risk of developing dementia. The glymphatic system is a recently characterised brain-wide cerebrospinal fluid and interstitial fluid drainage pathway that enables the clearance of interstitial metabolic waste from the brain parenchyma. Emerging data suggest that DM and ageing impair the glymphatic system, leading to accumulation of metabolic wastes including amyloid-ß within the brain parenchyma, and consequently provoking cognitive dysfunction. In this review, we concisely discuss recent findings regarding the role of the glymphatic system in DM and ageing associated cognitive impairment.

Modeling glymphatic system of the brain using MRI.

The glymphatic system is functional waste clearance path from the brain parenchyma through dynamic exchange of cerebrospinal fluid (CSF) with interstitial fluid (ISF). Impairment of glymphatic waste clearance is involved in the development of neurodegenerative conditions. Despite many recent studies investigating the glymphatic system, few studies have tried to use a mathematical model to describe this system, quantitatively. In this study, we aim to model the glymphatic system from the kinetics of Gd-DTPA tracer measured using MRI in order to: 1) map the glymphatic system path, 2) derive kinetic parameters of the glymphatic system, and 3) provide quantitative maps of the structure and function of this system. In the proposed model, the brain is clustered to similar regions with respect to the profile of contrast agent (CA) density measured by MRI. Then, each region is described as a two-compartment kinetic model 'derived from' or 'clears to' its neighbors with local input function. We thus fit our model to the local cerebral regions rather than to the averaged time signal curve (TSC) of the whole brain. The estimated parameters showed distinctive differences between diabetes mellitus (DM) and control rats. The results suggest that in a typical DM brain the CSF bulk speed in the para-vasculature network is low. In addition, the resulting maps indicate that there may be increased binding and decreased absorbing of large molecules in a diabetic compared with a non-diabetic brain. The important contribution of this work was to fit the model to the local regions rather than to the averaged time signal curve (TSC) of the whole brain. This enabled us to derive quantitative maps of the glymphatic system from MRI.

MRI investigation of glymphatic responses to Gd-DTPA infusion rates.

The glymphatic system is a newly identified waste clearance pathway in brain discovered and investigated predominately using in vivo two-photon confocal microscopy. Magnetic resonance imaging (MRI), in contrast to two-photon confocal microscopy, provides dynamic and real-time pictures of the glymphatic system in whole brain. We employ MRI to investigate the response of the glymphatic system to the rate of infusion of Gd-DTPA (magnevist). Wistar rats were subjected to a surgery of inserting a tube into the cisterna magna for infusion during MRI. Three infusion rates were chosen for 20 min infusions of diluted magnevist into the cerebrospinal fluid (CSF) of rat brain. Glymphatic response was imaged using dynamic MRI 3D measurement for 5 hr. Robust correlations were found in all ventricles between the peak intensities of image enhancement and infusion rates, with additional correlations between the peak times of MRI image enhancement and infusion rates in the fourth ventricle. An infusion rate of 2.92 µL/min induced an evident accumulation of tracer in the fourth ventricle near the cisterna magna. In hippocampal tissue, image enhancements exhibited low correlation with the infusion rates. However, an infusion rate of 1.67 µL/min provided a high image enhancement, but less tracer accumulation near the cisterna magna. Contrast-enhanced MRI provides a suitable tool for investigating image contrast infusion rate response of the glymphatic system in rat brain. Considering both T1 and T2* effects in response to the infused magnevist into CSF, the infusion rate of 1.67 µL/min appears suitable for MRI study of the glymphatic system in rat.