Fluids and Barriers of the CNS最新文献

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.

Brain metastases (BMs) are the most common intracranial tumors in adults and occur 3-10 times more frequently than primary brain tumors. Despite intensive multimodal therapies, including resection, radiotherapy, and chemotherapy, BMs are associated with poor prognosis and remain challenging to treat. BMs predominantly originate from primary lung (20-56%), breast (5-20%), and melanoma (7-16%) tumors, although they can arise from other cancer types less frequently. The metastatic cascade is a multistep process involving local invasion, intravasation into the bloodstream or lymphatic system, extravasation into normal tissue, and colonization of the distal site. After reaching the brain, circulating tumor cells (CTCs) breach the blood-brain barrier (BBB).The selective permeability of the BBB poses a significant challenge for therapeutic compounds, limiting the treatment efficacy of BMs. Understanding the mechanisms of tumor cell interactions with the BBB is crucial for the development of effective treatments. This review provides an in-depth analysis of the brain barriers, including the BBB, blood-spinal cord barrier, blood-meningeal barrier, blood-arachnoid barrier, and blood-cerebrospinal fluid barrier. It explores the molecular and cellular components of these barriers and their roles in brain metastasis, highlighting the importance of this knowledge for identifying druggable targets to prevent or limit BM formation.

Background: The pressure gradient between the ventricles and the subarachnoid space (transmantle pressure) is crucial for understanding CSF circulation and the pathogenesis of certain neurodegenerative diseases. This pressure can be approximated by the pressure difference across the aqueduct (ΔP). Currently, no dedicated platform exists for quantifying ΔP, and no research has been conducted on the impact of breathing on ΔP. This study aims to develop a post-processing platform that balances accuracy and ease of use to quantify aqueduct resistance and, in combination with real-time phase contrast MRI, quantify ΔP driven by free breathing and cardiac activities.

Methods: Thirty-four healthy participants underwent 3D balanced fast field echo (BFFE) sequence and real-time phase contrast (RT-PC) imaging on a 3T scanner. We used the developed post-processing platform to analyse the BFFE images to quantify the aqueduct morphological parameters such as resistance. RT-PC data were then processed to quantify peak flow rates driven by cardiac and free breathing activity (Qc and Qb) in both directions. By multiplying these Q by resistance, ΔP driven by cardiac and breathing activity was obtained (ΔPc and ΔPb). The relationships between aqueduct resistance and flow rates and ΔP driven by cardiac and breathing activity were analysed, including a sex difference analysis.

Results: The aqueduct resistance was 78 ± 51 mPa·s/mm³. The peak-to-peak cardiac-driven ΔP (Sum of ΔPc⁺ and ΔPc^-) was 24.2 ± 11.4 Pa, i.e., 0.18 ± 0.09 mmHg. The peak-to-peak breath-driven ΔP was 19 ± 14.4 Pa, i.e., 0.14 ± 0.11 mmHg. Males had a longer aqueduct than females (17.9 ± 3.1 mm vs. 15 ± 2.5 mm, p < 0.01) and a larger average diameter (2.0 ± 0.2 mm vs. 1.8 ± 0.3 mm, p = 0.024), but there was no gender difference in resistance values (p = 0.25). Aqueduct resistance was negatively correlated with stroke volume and the peak cardiac-driven flow (p < 0.05); however, there was no correlation between aqueduct resistance and breath-driven peak flow rate.

Conclusions: The highly automated post-processing software developed in this study effectively balances ease of use and accuracy for quantifying aqueduct resistance, providing technical support for future research on cerebral circulation physiology and the exploration of new clinical diagnostic methods. By integrating real-time phase contrast MRI, this study is the first to quantify the aqueduct pressure difference under the influence of free breathing. This provides an important physiological reference for further studies on the impact of breathing on transmantle pressure and cerebral circulation mechanisms.

Hydrocephalus is a neurological disorder that impacts approximately 85 per 100,000 individuals worldwide and is associated with motor and cognitive impairments. While many advances in surgical interventions have helped substantially improve the survival rates and quality of life of those affected, there continues to be significant gaps in our understanding of the etiology of this heterogeneous condition as well as its specific neuropsychological and functional challenges across different phases of life. To address these limitations, the Hydrocephalus Association and Rudi Schulte Research Institute organized a workshop titled, "Improving Cognitive and Psychological Outcomes in Hydrocephalus", composed of top academics in the fields of hydrocephalus, cognition, and neuropsychology, as well as individuals with hydrocephalus or their caregivers. The purpose was to review the available evidence and propose pertinent areas of further research to improve the cognitive functioning, functional status, and quality of life of individuals with hydrocephalus. These topics included cognitive and neuropsychological assessments and daily-life function of children and adults living with hydrocephalus, biomarkers of cognitive function, animal modeling of hydrocephalus, and the longitudinal impact of hydrocephalus treatment. The following paper outlines four primary areas that warrant research: (1) neuropsychological phenotypes, (2) treatment-focused research considerations, (3) translational pre-clinical tools, and (4) establishing pathways for longitudinal care. Through the efforts of this group, the goal of this manuscript is to inspire and direct scientific and clinical inquiry towards these noted research priorities to further improve the lives of individuals with hydrocephalus and their families.

Background: Disproportionately enlarged subarachnoid space hydrocephalus (DESH) is one of the neuroradiological characteristics of idiopathic normal pressure hydrocephalus (iNPH), which makes statistical analyses of brain images difficult. This study aimed to develop and validate methods of accurate brain segmentation and spatial normalisation in patients with DESH by using the Computational Anatomy Toolbox (CAT12).

Methods: Two hundred ninety-eight iNPH patients with DESH and 25 healthy controls (HCs) who underwent cranial MRI were enrolled in this study. We selected the structural images of 169 patients to create customised tissue probability maps and diffeomorphic anatomical registration through exponentiated Lie algebra (DARTEL) templates for patients with DESH (DESH-TPM and DESH-Template). The structural images of 38 other patients were used to evaluate the validity of the DESH-TPM and DESH-Template. DESH-TPM and DESH-Template were created using the 114 well-segmented images after the segmentation processing of CAT12. In the validation study, we compared the accuracy of brain segmentation and spatial normalisation among three conditions: customised condition, applying DESH-TPM and DESH-Template to CAT12 and patient images; standard condition, applying the default setting of CAT12 to patient images; and reference condition, applying the default setting of CAT12 to HC images.

Results: In the validation study, we identified three error types during segmentation. (1) The proportions of misidentifying the dura and/or extradural structures as brain structures in the customised, standard, and reference conditions were 10.5%, 44.7%, and 13.6%, respectively; (2) the failure rates of white matter hypointensity (WMH) cancellation in the customised, standard, and reference conditions were 18.4%, 44.7%, and 0%, respectively; and (3) the proportions of cerebrospinal fluid (CSF)-image deficits in the customised, standard, and reference conditions were 97.4%, 84.2%, and 28%, respectively. The spatial normalisation accuracy of grey and white matter images in the customised condition was the highest among the three conditions, especially in terms of superior convexity.

Conclusions: Applying the combination of the DESH-TPM and DESH-Template to CAT12 could improve the accuracy of grey and white matter segmentation and spatial normalisation in patients with DESH. However, this combination could not improve the CSF segmentation accuracy. Another approach is needed to overcome this challenge.

Background: Cerebrospinal fluid (CSF) motion and pulsatility has been proposed to play a crucial role in clearing brain waste. Although its driving forces remain debated, increasing evidence suggests that large amplitude vasomotion drives such CSF fluctuations. Recently, a fast blood-oxygen-level-dependent (BOLD) fMRI sequence was used to measure the coupling between CSF fluctuations and low-frequency hemodynamic oscillations in the human cortex. However, this technique is not quantitative, only captures unidirectional flow and is sensitive to B0-fluctuations. Real-time phase contrast (pcCSF) instead measures CSF flow dynamics in a fast, quantitative, bidirectional and B0-insensitive manner, but lacks information on hemodynamic brain oscillations. In this study we propose to combine the strengths of both sequences by interleaving real-time phase contrast with a cortical BOLD scan, thereby enabling the quantification of the interaction between CSF flow and cortical BOLD.

Methods: Two experiments were performed. First, we compared the CSF flow measured using real-time phase contrast (pcCSF) with the inflow-sensitized BOLD (iCSF) measurements by interleaving both techniques at the repetition level and planning them at the same location. Next, we compared the BOLD-CSF coupling obtained using the novel pcCSF interleaved with cortical BOLD to the coupling obtained with the original iCSF. To time-lock the CSF fluctuations, participants were instructed to perform slow, abdominal paced breathing.

Results: pcCSF captures bidirectional CSF dynamics with a more pronounced in- and outflow curve than the original iCSF method. With the pcCSF method, the BOLD-CSF coupling was stronger (mean cross-correlation peak increase = 0.22, p = .008) and with a 1.9 s shorter temporal lag (p = .016), as compared to using the original iCSF technique.

Conclusions: In this study, we introduce a new method to study the coupling of CSF flow measured in the fourth ventricle to cortical BOLD fluctuations. In contrast to the original approach, the use of phase contrast MRI to measure CSF flow provides a quantitative in- and outflow curve, and improved BOLD-CSF coupling metrics.