Fluids and Barriers of the CNS最新文献

Background: Patients with the genetic disorder Niemann-Pick type C2 disease (NP-C2) suffer from lysosomal accumulation of cholesterol causing both systemic and severe neurological symptoms. In a murine NP-C2 model, otherwise successful intravenous Niemann-Pick C2 protein (NPC2) replacement therapy fails to alleviate progressive neurodegeneration as infused NPC2 cannot cross the blood-brain barrier (BBB). Genetic modification of brain endothelial cells (BECs) is thought to enable secretion of recombinant proteins thereby overcoming the restrictions of the BBB. We hypothesized that an adeno-associated virus (AAV-BR1) encoding the Npc2 gene could cure neurological symptoms in Npc2-/- mice through transduction of BECs, and possibly neurons via viral passage across the BBB.

Methods: Six weeks old Npc2-/- mice were intravenously injected with the AAV-BR1-NPC2 vector. Composite phenotype scores and behavioral tests were assessed for the following 6 weeks and visually documented. Post-mortem analyses included gene expression analyses, verification of neurodegeneration in Purkinje cells, determination of NPC2 transduction in the CNS, assessment of gliosis, quantification of gangliosides, and co-detection of cholesterol with NPC2 in degenerating neurons.

Results: Treatment with the AAV-BR1-NPC2 vector improved motor functions, reduced neocortical inflammation, and preserved Purkinje cells in most of the mice, referred to as high responders. The vector exerted tropism for BECs and neurons resulting in a widespread NPC2 distribution in the brain with a concomitant reduction of cholesterol in adjacent neurons, presumably not transduced by the vector. Mass spectrometry imaging revealed distinct lipid alterations in the brains of Npc2-/- mice, with increased GM2 and GM3 ganglioside accumulation in the cerebellum and hippocampus. AAV-BR1-NPC2 treatment partially normalized these ganglioside distributions in high responders, including restoration of lipid profiles towards those of Npc2+/+ controls.

Conclusion: The data suggests cross-correcting gene therapy to the brain via delivery of NPC2 from BECs and neurons.

Primary ciliary dyskinesia (PCD) is a genetic disorder causing motile ciliary dysfunction primarily affecting the respiratory and reproductive systems. However, the impact of PCD on the central nervous system remains poorly understood. Rodent models of PCD exhibit marked hydrocephalus leading to early animal mortality, however, most humans with PCD do not develop hydrocephalus for unknown reasons. We hypothesized that patients with PCD exhibit sub-clinical ventriculomegaly related to ependymal motile ciliary dysfunction. We demonstrated highly specific expression levels of known PCD-related genes in human brain multiciliated ependymal cells (p < 0.0001). To assess ventricular size, computed tomography sinus images from patients with PCD (n = 33) and age/sex-matched controls (n = 64) were analysed. Patients with PCD displayed significantly larger ventricular areas (p < 0.0001) and Evans index (p < 0.01), indicating ventriculomegaly that was consistent across all genetic subgroups. Ventricular enlargement correlated positively with increasing age in patients with PCD compared to controls (p < 0.001). Additionally, chart review demonstrated a high prevalence (39%) of neuropsychiatric/neurological disorders in adult PCD patients that did not correlate with degree of ventriculomegaly. Our findings suggest that patients with PCD may have unrecognized, mild ventriculomegaly which correlates with ageing, potentially attributable to ependymal ciliary dysfunction. Further study is required to determine causality, and whether ventricular enlargement contributes to neuropsychiatric/neurological or other morbidity in PCD.

Background: Therapeutic antibodies for the treatment of neurological disease show great potential, but their applications are rather limited due to limited brain exposure. The most well-studied approach to enhance brain influx of protein therapeutics, is receptor-mediated transcytosis (RMT) by targeting nutrient receptors to shuttle protein therapeutics over the blood-brain barrier (BBB) along with their endogenous cargos. While higher brain exposure is achieved with RMT, the timeframe is short due to rather fast brain clearance. Therefore, we aim to increase the brain half-life of antibodies by binding to myelin oligodendrocyte glycoprotein (MOG), a CNS specific protein.

Methods: Alpaca immunization with mouse/human MOG, and subsequent phage selections and screenings for MOG binding single variable domain antibodies (VHHs) were performed to find mouse/human cross-reactive VHHs. Their ability to increase the brain half-life of antibodies was evaluated in healthy wild-type mice by coupling two different MOG VHHs (low/high affinity) in a mono- and bivalent format to a β-secretase 1 (BACE1) inhibiting antibody or a control (anti-SARS-CoV-2) antibody, fused to an anti-transferrin receptor (TfR) VHH for active transport over the BBB. Brain pharmacokinetics and pharmacodynamics, CNS and peripheral biodistribution, and brain toxicity were evaluated after intravenous administration to balb/c mice.

Results: Additional binding to MOG increases the C_max and brain half-life of antibodies that are actively shuttled over the BBB. Anti-SARS-CoV-2 antibodies coupled with an anti-TfR VHH and two low affinity anti-MOG VHHs could be detected in brain 49 days after a single intravenous injection, which is a major improvement compared to an anti-SARS-CoV-2 antibody fused to an anti-TfR VHH which cannot be detected in brain anymore one week post treatment. Additional MOG binding of antibodies does not affect peripheral biodistribution but alters brain distribution to white matter localization and less neuronal internalization.

Conclusions: We have discovered mouse/human/cynomolgus cross-reactive anti-MOG VHHs which have the ability to drastically increase brain exposure of antibodies. Combining MOG and TfR binding leads to distinct PK, biodistribution, and brain exposure, differentiating it from the highly investigated TfR-shuttling. It is the first time such long brain antibody exposure has been demonstrated after one single dose. This new approach of adding a binding moiety for brain specific targets to RMT shuttling antibodies is a huge advancement for the field and paves the way for further research into brain half-life extension.

Background: Acute and critical neurological diseases are often accompanied with elevated intracranial pressure (ICP), leading to insufficient cerebral perfusion, which may cause severe secondary lesion. Existing ICP monitoring techniques often fail to effectively meet the demand for real-time noninvasive ICP monitoring and warning. This study aimed to explore the use of electrical impedance tomography (EIT) to provide real-time early warning of elevated ICP by observing cerebral perfusion.

Methods: An intracranial hypertension model was prepared by injecting autologous un-anticoagulated blood into the brain parenchyma of twelve Landrace swine. Invasive ICP monitoring was used as a control method, and a high-precision EIT system was used to acquire and analyze the changing patterns of cerebral perfusion EIT image parameters with respect to ICP. Four EIT parameters related to cerebral perfusion were extracted from the images, and their potential application in detecting ICP elevation was analyzed.

Results: When ICP increased, all EIT perfusion parameters decreased significantly (P < 0.05). When the subjects were in a state of intracranial hypertension (ICP > 22 mmHg), the correlation between EIT perfusion parameters and ICP was more significant (P < 0.01), with correlation coefficients ranging from -0.72 to -0.83. We tested the objects when they were in baseline ICP and in ICP of 15-40 mmHg. Under both circumstances, ROC curve analysis showed that the comprehensive model of perfusion parameters based on the random forest algorithm had a sensitivity and specificity of more than 90% and an area under the curve (AUC) of more than 0.9 for detecting ICP increments of both 5 and 10 mmHg.

Conclusion: This study demonstrates the feasibility of using perfusion EIT to detect ICP increases in real time, which may provide a new method for real-time non-invasive monitoring of patients with increased ICP.

Background: The approval of new disease-modifying therapies by the U.S. Food and Drug Administration and the European Medicine Agency makes it necessary to optimize non-invasive and cost-effective tools for the identification of subjects at-risk of developing Alzheimer's Disease (AD). Plasma biomarkers are excellent candidates. However, their ability to reflect the cerebrospinal fluid (CSF) profile - that remains to date the gold standard for the biochemical diagnosis of AD - needs to be confirmed and validated before their implementation in clinical practice. The aims of this study are to analyse the correlation between CSF and plasma Aβ40, Aβ42, Aβ42/Aβ40 and pTau181, and to assess the diagnostic performance of plasma biomarkers in a cohort of subjects affected by Mild Cognitive Impairment (MCI).

Methods: The study was performed on 306 subjects affected by MCI, enrolled in the context of the Italian Interceptor Project. Aβ40, Aβ42 and pTau181 were analysed in plasma and CSF, and pTau217 was measured in plasma. The fully automated chemiluminescence enzyme immunoassay and the Lumipulse^® G600II (Fujirebio) instrument were used for all measurements. We analysed the correlations between CSF and plasma biomarkers and the differences of plasma biomarker concentrations after grouping MCI cases according to AT classification of CSF AD biomarker profiles.

Results: We found statistically significant positive correlations between CSF and plasma Aβ42, Aβ42/Aβ40 ratio and pTau181. All the biomarkers, except Aβ40, showed differences in A+ vs. A-, A+T+ vs. A-T- and A+T- vs. A-T- patients. Moreover, Aβ42 and Aβ42/Aβ40 plasma levels were lower in A+T- compared to A-T- and A-T+ groups, and pTau181 and pTau217 plasma levels were higher in A+T+ compared to A+T-. Aβ42/Aβ40 and pTau217 showed a robust performance in distinguishing A+ from A- (AUC = 0.857 and 0.862, respectively) and A+T+ from A-T- (AUC = 0.866 and 0.911) subjects.

Conclusions: Our results suggest that plasma biomarkers, and especially Aβ42/Aβ40 ratio and pTau217, are promising candidates for the early detection of AD pathology.

Oxidative stress and neuronal apoptosis could be an important factor leading to post-hemorrhagic consequences after germinal matrix hemorrhage (GMH). Previously study have indicated that relaxin 2 receptor activation initiates anti-oxidative stress and anti-apoptosis in ischemia-reperfusion injury. However, whether relaxin 2 activation can attenuate oxidative stress and neuronal apoptosis after GMH remains unknown. To investigate the beneficial effect of relaxin 2 on oxidative stress injury and neuronal apoptosis by GMH, a total of 150 rat pups were subjected to GMH by an intraparenchymal injection of bacterial collagenase. Recombinant human relaxin-2 (rh-relaxin-2) was administered intraperitoneally injections at 1 h and 13 h after GMH. Lenti-virus with sgRXFP1 and sgCtrl was administered intracerebroventricular (i.c.v.) on the left side of the brain to inhibit the RXFP1 at 2d prior to GMH induction, and LY321499, ERK inhibitor, was administered by i.c.v. injection at 1 h on the left side of the brain prior to GMH induction, respectively. Co-immunoprecipitation, immunofluorescence, TUNEL, Fluoro-Jade C, DHE staining, western blot, Nitrix Oxide (NO) quantification and side effect experiments were performed to evaluate post-GMH. We found endogenous relaxin-2 interacts with RXFP1 and both protein colocalized in neurons on the first day after GMH. Additionally, RXFP1 activation with rh-relaxin-2 significantly inhibited oxidative stress and neuronal apoptosis in GMH + rh-relaxin-2 group compared with GMH + vehicle group. Moreover, rh-relaxin-2 treatment significantly inhibited the phosphorylation of ERK and nNOS, as well as upregulated expression of Bcl2 and NO and downregulated expression of Bax and Romo 1. The beneficial effects of rh-relaxin-2 were reversed by i.c.v. injection of lenti-virus with sgRXFP1 and LY321499, respectively. Furthermore, the side effect experiment showed rh-relaxin-2 did not affect neurological behavior and the function of liver and kidney. In conclusion, our finding showed that rh-relaxin-2 attenuated oxidative stress and neuronal apoptosis after GMH through RXFP1-ERK-nNOS-NO signaling pathway.

Background: Iduronate-2-sulfatase (IDS) deficiency (MPS II; Hunter syndrome) is a disorder that exhibits peripheral and CNS pathology. The blood brain barrier (BBB) prevents systemic enzyme replacement therapy (ERT) from alleviating CNS pathology. We aimed to enable brain delivery of systemic ERT by using molecular BBB-Trojans targeting endothelial transcytosis receptors.

Methods: Single-domain antibody (sdAb)-enzyme fusion protein constructs were prepared in Yarrowia lipolytica. sdAb affinity and BBB permeability were characterized using SPR and an in vitro rodent BBB assay, respectively. In vivo pharmacokinetic (PK) analysis was performed in rats. Quantification of fusion protein amounts were performed using LC-MS.

Results: Fusion proteins consisting of IDS and BBB-transmigrating sdAbs, albumin binding sdAbs or human serum albumin (HSA) were evaluated for their in vitro BBB permeability. IGF1R3H5-IDS was selected for in vivo PK analysis in rats. IDS and IGF1R3H5-IDS exhibited very short (< 10 min) serum half-life (t_1/2α), while constructs containing either HSA or anti-serum albumin sdAbs (R28 or M79) showed 8-11 fold increases in the area under the curve (AUC) in serum. CSF analysis indicated that IGF1R3H5 increased brain exposure by 9 fold (AUC) and constructs containing HSA or R28 exhibited 42-52 fold increases. Quantitation of brain levels confirmed the increased and sustained delivery of IDS to the brain of HSA- and R28-containing constructs. Lastly, analysis of brain fractions demonstrated that the increases in brain tissue were due to parenchymal delivery without fusion protein accumulation in brain vessels.

Conclusions: These results demonstrate the utility of IGF1R-targeting sdAbs to effect brain delivery of lysosomal enzymes, as well as the utility of serum albumin-targeting sdAbs in t_1/2 extension, to increase brain delivery of rapidly cleared enzymes.

Background: Traumatic spinal cord injury (SCI) causes spinal cord swelling and occlusion of the subarachnoid space (SAS). SAS occlusion can change pulsatile cerebrospinal fluid (CSF) dynamics, which could have acute clinical management implications. This study aimed to characterise SAS occlusion and investigate CSF dynamics over 14 days post-SCI in the pig.

Methods: A thoracic contusion SCI was induced in female domestic pigs (22-29 kg) via a weight drop apparatus (N = 5, 10 cm; N = 5, 20 cm). Magnetic resonance imaging (MRI) was performed pre-SCI and 3, 7 and 14 days post-SCI. SAS occlusion length (cranial-caudal), and injury site SAS area (cross-sectional), were measured on T2-weighted MRI. CSF dynamics, specifically peak cranial/caudal mean velocity (cm/s), and the corresponding time to peak (% of cardiac cycle), were measured on cardiac gated, axial phase-contrast MRI obtained at C2/C3, T8/T9, T11/T12 and L1/L2. Linear-mixed effects models, with a significance level of α = 0.05, were developed to assess the effect of: (1) injury group and time point on SAS occlusion measures; and (2), time point and spinal level, adjusted by injury group, on CSF dynamics.

Results: For both injury groups, SAS occlusion length decreased from 3 to 7 days post-SCI, and 7 to 14 days post-SCI. The cross-sectional SAS area decreased after SCI, and increased to 14 days post-SCI, in both groups. At all spinal levels, peak cranial/caudal mean velocity and the time to peak caudal mean velocity decreased at day 3 post-SCI. From 3 to 14 days post-SCI, peak caudal mean velocity and the time to peak caudal mean velocity increased towards baseline values, at all spinal levels.

Conclusions: Spinal-level specific changes to CSF dynamics, with concurrent changes to SAS occlusion, occurred after SCI in the pig, suggesting that CSF pulsatility and craniospinal compliance were altered in the sub-acute post-traumatic period. These results suggest that PC-MRI derived CSF dynamics may provide a non-invasive method to investigate functional alterations to the spinal intrathecal space following traumatic SCI.

Background: Cerebral autoregulation is a robust regulatory mechanism that stabilizes cerebral blood flow in response to reduced blood pressure, thereby preventing cerebral ischaemia. Scientists have long believed that cerebral autoregulation also stabilizes cerebral blood flow against increases in intracranial pressure, which is another component that determines cerebral perfusion pressure. However, this idea was inconsistent with the complex pathogenesis of normal pressure hydrocephalus, which includes components of chronic cerebral ischaemia due to mild increases in intracranial pressure.

Methods: Twenty-one patients who underwent ventriculoperitoneal shunt surgery for normal pressure hydrocephalus were included in this study. To determine the pressure setting of the Codman-Hakim programmable valve, intracranial pressure was measured after shunt surgery by puncturing the Ommaya reservoir, which formed a closed circuit with the needle and the syringe. Then, intracranial pressure was continuously measured with intermittent infusion of cerebrospinal fluid from the same closed circuit. We also continuously measured oximetry data, such as regional cerebral oxygen saturation derived from near-infrared spectroscopy monitoring. These data were digitized, recorded, and used for calculating intracranial compliance and the relationship between cerebrospinal fluid volume loading and intracranial pressure.

Results: This study demonstrates that in patients with normal pressure hydrocephalus, cerebral venous vascular bed compression induces mild cerebral ischaemia when intracranial pressure is slightly higher than physiological venous pressure. Cerebral venous compression impairs cerebral blood flow by quadratically increasing circulatory resistance according to Poiseuille's law. Furthermore, chronic cerebral ischaemia occurred even at low or normal intracranial pressures when deep and subcortical white matter hyperintensities (DSWMHs) were severe.

Conclusion: The fact that cerebral blood flow impairment begins at very low intracranial pressures indicates that cerebral autoregulation to compensate for reduced venous blood flow is not functioning adequately in NPH. These processes provide a link between impaired cerebrospinal fluid circulation, cerebral autoregulation, and neurological dysfunction, which has been missing in patients with NPH involving small vessel arteriosclerosis. These findings may provide insight into similar conditions, such as normal-tension glaucoma and chronic kidney disease, in which a mild increase in local compartment pressure leads to chronic ischemia in organs protected by autoregulatory mechanisms.

Background: Blood-brain barrier dysfunction is one characteristic of Alzheimer's disease (AD) and is recognized as both a cause and consequence of the pathological cascade leading to cognitive decline. The goal of this study was to assess markers for barrier dysfunction in postmortem tissue samples from research participants who were either cognitively normal individuals (CNI) or diagnosed with AD at the time of autopsy and determine to what extent these markers are associated with AD neuropathologic changes (ADNC) and cognitive impairment.

Methods: We used postmortem brain tissue and plasma samples from 19 participants: 9 CNI and 10 AD dementia patients who had come to autopsy from the University of Kentucky AD Research Center (UK-ADRC) community-based cohort; all cases with dementia had confirmed severe ADNC. Plasma samples were obtained within 2 years of autopsy. Aβ40, Aβ42, and tau levels in brain tissue samples were quantified by ELISA. Cortical brain sections were cleared using the X-CLARITY^™ system and immunostained for neurovascular unit-related proteins. Brain slices were then imaged using confocal microscopy and analyzed for microvascular diameters and immunoreactivity coverage using Fiji/ImageJ. Isolated human brain microvessels were assayed for tight-junction protein expression using the JESS™ automated Western blot system. S100 calcium-binding protein B (S100β), matrix metalloproteinase (MMP)-2, MMP-9, and neuron-specific enolase (NSE) levels in plasma were quantified by ELISA. All outcomes were assessed for linear associations with global cognitive function (MMSE, CDR) and cerebral atrophy scores by Pearson, polyserial, or polychoric correlation, as appropriate, along with generalized linear modeling or generalized linear mixed-level modeling.

Results: As expected, we detected elevated Aβ and tau pathology in brain tissue sections from AD patients compared to CNI. However, we found no differences in microvascular diameters in cleared AD and CNI brain tissue sections. We also observed no differences in claudin-5 protein levels in capillaries isolated from AD and CNI tissue samples. Plasma biomarker analysis showed that AD patients had 12.4-fold higher S100β plasma levels, twofold lower NSE plasma levels, 2.4-fold higher MMP-9 plasma levels, and 1.2-fold lower MMP-2 plasma levels than CNI. Data analysis revealed that elevated S100β plasma levels were predictive of AD pathology and cognitive impairment.

Conclusion: Our data suggest that among different markers relevant to barrier dysfunction, plasma S100β is the most promising diagnostic biomarker for ADNC. Further investigation is necessary to assess how plasma S100β levels relate to these changes and whether they may predict clinical outcomes, particularly in the prodromal and early stages of AD.