Protective effect of brain-derived neurotrophic factor on retinal neurovascular unit / 国际眼科杂志(Guoji Yanke Zazhi)

Based on the neurovascular unit(NVU), neurovascular coupling functions as a barrier to maintain the homeostasis of the microenvironment by regulating the signaling and metabolic activity of nerve cells and capillaries. Widely dispersed across the retina, the NVU is essential to preserving its normal physiological function. A disturbance in retinal neurovascular homeostasis produced by a range of factors can result in a variety of retinal disorders, such as diabetic retinopathy(DR), glaucoma, retinitis pigmentosa(RP)and age-related macular degeneration(ARMD). The retina also has a widespread distribution of brain-derived neurotrophic factor(BDNF), which functions to promote neuron growth and repair damage by binding to its receptor TrkB. In recent years, BDNF was found to play a protective role against damage in the early stage of retinal neurovascular homeostasis imbalance, often known as the neurodegenerative stage. It also helps to reduce the production of pro-angiogenic substances of neurological origin and offers a fresh approach for the early detection and treatment of associated eye disorders.

Neurovascular unit and diabetic retinopathy / 国际眼科杂志(Guoji Yanke Zazhi)

The concept of neurovascular unit(NVU), formalized in 2001 at a stroke conference, emphasizes the intimate relationship between the brain and its vessels, i.e., symbiotic relationship between brain cells and cerebral blood vessels in the developmental, structural and functional interdependence. The retina is a piece of brain. Several researchers have introduced the concept of NVU to the retina since 2007. The NVU in the retina includes neurons, glial cells, microvascular endothelial cells and pericytes. Dysfunctional NVU plays a critical role in diabetic retinopathy(DR). The current limited treatments for DR focus on the late-stage complications, i.e., diabetic macular edema and proliferative DR. While the further study on retinal NVU will develop efficacious therapeutic options for the early and all stages of DR.

Altered neurovascular coupling in arteriosclerotic cerebral small vessel disease and the correlation with cognitive function / 中华神经科杂志

Objective:To investigate the global and local changes of neurovascular coupling in arteriosclerotic cerebral small vessel disease (aCSVD) and the correlation with cognitive function.Methods:Forty-three patients with confirmed aCSVD from the outpatient department or ward of the Department of Neurology, the First Affiliated Hospital of Anhui Medical University between June 2020 and June 2021 were enrolled in this study. Meanwhile, 48 healthy subjects were selected as controls. Cognitive evaluation, resting-state functional magnetic resonance imaging and 3D pseudo-continuous arterial spin labeling magnetic resonance imaging scanning were performed in all subjects. The global cerebral blood flow-regional homogeneity (ReHo) correlation coefficient and the cerebral blood flow/ReHo ratio were used to evaluate global and local neurovascular coupling. Meanwhile, correlations between the cerebral blood flow/ReHo ratio and neuropsychological assessments were explored in aCSVD patients.Results:Global cerebral blood flow-ReHo coupling was decreased in aCSVD patients compared to healthy controls [aCSVD patients: 0.942(0.933, 0.950), healthy controls: 0.947(0.939, 0.954), Z=-2.11, P=0.035]. aCSVD patients showed decreased cerebral blood flow/ReHo ratio in the right lingual gyrus ( t=-4.45, P<0.05) and increased cerebral blood flow/ReHo ratio in the left ( t=4.91, P<0.05) and right ( t=4.72, P<0.05) inferior parietal lobule. Cerebral blood flow/ReHo ratio of the right inferior parietal lobule was negatively correlated with total score ( r=-0.33, P=0.031) and praxis score ( r=-0.43, P=0.004) in Cambridge Cognitive Examination-Chinese Version subitems and positively correlated with scores of Stroop Color Word Test (SCWT)-color ( r=0.33, P=0.032), SCWT-word ( r=0.34, P=0.025) and Trail Making Test-B ( r=0.31, P=0.043) in aCSVD patients. While the cerebral blood flow/ReHo ratio of the right lingual gyrus was negatively correlated with Visual Replicate-Immediate Recall score ( r=-0.36, P=0.017). Conclusion:aCSVD patients showed abnormal global and local neurovascular coupling, which was associated with attention, executive function, and visual space function.

Neurovascular coupling analysis of working memory based on electroencephalography and functional near-infrared spectroscopy / 生物医学工程学杂志

Working memory is an important foundation for advanced cognitive function. The paper combines the spatiotemporal advantages of electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) to explore the neurovascular coupling mechanism of working memory. In the data analysis, the convolution matrix of time series of different trials in EEG data and hemodynamic response function (HRF) and the blood oxygen change matrix of fNIRS are extracted as the coupling characteristics. Then, canonical correlation analysis (CCA) is used to calculate the cross correlation between the two modal features. The results show that CCA algorithm can extract the similar change trend of related components between trials, and fNIRS activation of frontal pole region and dorsolateral prefrontal lobe are correlated with the delta, theta, and alpha rhythms of EEG data. This study reveals the mechanism of neurovascular coupling of working memory, and provides a new method for fusion of EEG data and fNIRS data.

Role of neurovascular units in cerebral small vessel disease / 国际脑血管病杂志

Cerebral small vessel disease (CSVD) is a common cerebrovascular disease in clinical practice. Its onset is hidden and its clinical manifestations are diverse. Studies have shown that there are pleiotropic effects and recurrent activation phenomenon between the functional imbalance of neurovascular unit (NVU) and a series of pathophysiological processes, such as vascular endothelial dysfunction, blood-brain barrier permeability change and glial cell activation, which jointly promote the progress of CSVD under the action of inflammatory and immune factors. This article reviews the role of NVU in the occurrence and development of CSVD.

Role of neurovascular dysfunction in vascular cognitive impairment and Alzheimer's disease / 国际脑血管病杂志

The neurovascular unit consists of neurons, glial cells and cerebral blood vessels. Each eomponent synergistically regulates vasomotion and maintains the blood-brain barrier function to maintain the microenvironment homeostasis and ensure normal brain function. Cognitive impairment, especially in the advanced stage of dementia, places heavy economic and mental burdens on society and families. From the perspective of holistic view, this article expounds the role of neurovascular dysfuntion in the two major causes of cognitive impairment, including Alzheimer's disease and vascular cognitive impairment, and aims to provide possible clues for early prevention and treatment of these diseases.

Research progress on the mechanism of the neurovascular coupling modulation / 中国脑血管病杂志

The neural activity and cognitive function require sophisticated regulation of blood flow in order to supply enough oxygen and glucose to the human brain. As a vital mechanism of cerebral blood flow autoregulation, neurovascular coupling (NVC) has characteristics of multiple channels and rapid response. Three physiological mechanisms in cortex, subcortex and postganglion were summarized, and the relationship between ischemia or hypoxia and NVC dysfunction was discussed in this article. In addition,the prospect of NVC mechanism study was addressed so as to provide new idea and target for treating cerebrovascular diseases.

Influences of different frequencies of repetitive transcranial magnetic stimulation on neurovascular coupling in contralateral motor region / 医疗卫生装备

Object To investigate the changes of neurovascular coupling (NVC) in the contralateral cerebral motor region under the action of repetitive transcranial magnetic stimulation (rTMS) at different frequencies. Methods Some experiments were designed, the electroencephalography (EEG) signals and the near-infrared spectra (NIRS) of the subjects were obtained under different rTMS stimulation frequencies, and EEG power spectrum of each frequency band and NIRS blood oxygen signals to the contralateral movement area were computed and the change characteristics and correlation were analyzed.Results For different stimulation frequencies, the energy of each frequency band of EEG increased after the stimulation, and then decreased rapidly. The oxyhemoglobin (HbO2) concentration was decreased during stimulation, and then raised. The change rate of the two signals varied with different stimulation frequencies, while the change trend was the same.The EEG power spectrum was negatively correlated with the change of HbO2 concentration after stimulation, and it had delayed effect in varying degrees in the period after stimulation.Conclusion The effect of rTMS on the coupling of nerves and vessels in the contralateral cerebral motor region can be reliably revealed by the study of EEG combined with NIRS. This study will be helpful to the development of effective RTMS treatment parameters, and the results are expected to be applied in clinical treatment.

Application value of functional transcranial Doppler ultrasound in the evaluation of neurovascular coupling function / 国际脑血管病杂志

Neurovascular coupling (NVC) is the basis of neuronal activity and metabolism, and its dysfunction may be closely associated with the occurrence and development of the nervous system diseases. Functional transcranial doppler ultrasonography (fTCD) can evaluate the NVC function. FTCD researches have shown that ischemic stroke, vascular cognitive impairment and other patients have NVC dysfunction. This article reviews the methods of fTCD examination of NVC and its clinical application.

Interrelationships between the Retinal Neuroglia and Vasculature in Diabetes

For years, diabetic retinopathy has been defined based on vascular lesions, and neural abnormalities were not regarded as important. This review summarizes evidence that the neural retina has important effects on the retinal vasculature under normal conditions, and the interaction between the retinal neuroglial cells and vascular function is altered in diabetes. Importantly, new evidence raises a possibility that abnormalities within retinal neuroglial cells (notably photoreceptors) might actually be causing or initiating the vascular disease in diabetic retinopathy.

Cerebral hemodynamics: concepts of clinical importance / Hemodinâmica encefálica: conceitos de importância clínica

Cerebral hemodynamics and metabolism are frequently impaired in a wide range of neurological diseases, including traumatic brain injury and stroke, with several pathophysiological mechanisms of injury. The resultant uncoupling of cerebral blood flow and metabolism can trigger secondary brain lesions, particularly in early phases, consequently worsening the patient's outcome. Cerebral blood flow regulation is influenced by blood gas content, blood viscosity, body temperature, cardiac output, altitude, cerebrovascular autoregulation, and neurovascular coupling, mediated by chemical agents such as nitric oxide (NO), carbon monoxide (CO), eicosanoid products, oxygen-derived free radicals, endothelins, K+, H+, and adenosine. A better understanding of these factors is valuable for the management of neurocritical care patients. The assessment of both cerebral hemodynamics and metabolism in the acute phase of neurocritical care conditions may contribute to a more effective planning of therapeutic strategies for reducing secondary brain lesions. In this review, the authors have discussed concepts of cerebral hemodynamics, considering aspects of clinical importance.

Alterações hemodinâmicas e metabólicas do encéfalo ocorrem frequentemente em diversas doenças neurológicas, principalmente em condições de traumatismo cranioencefálico e acidente vascular encefálico, com vários mecanismos patofisiológicos lesionais. O desacoplamento resultante do fluxo sanguíneo e do metabolismo encefálico pode resultar em lesões encefálicas secundárias, principalmente nas primeiras fases, e, consequentemente, no agravamento do desfecho neurológico dos pacientes. Diversos fatores influenciam o fluxo sanguíneo encefálico, entre eles, a concentração sanguínea de gases, viscosidade sanguínea, temperatura corpórea, débito cardíaco, altitude, autorregulação cerebrovascular e acoplamento neurovascular, que é mediado por óxido nítrico (ON), monóxido de carbono (CO), eicosanoides, radicais livres derivados do oxigênio, endotelinas, potássio, íons hidrogênio e adenosinas. Melhor compreensão destes fatores é fundamental para o manejo clínico dos pacientes neurológicos críticos. A avaliação hemodinâmica e metabólica do encéfalo nas lesões encefálicas agudas pode contribuir para o planejamento de estratégias de redução das lesões encefálicas secundárias. Nesta revisão, os autores discutiram princípios da hemodinâmica encefálica, considerando os aspectos de importância clínica.

Neurovascular coupling and functional neuroimaging in epilepsy / Acoplamento neurovascular e neuroimagem funcional em epilepsia

INTRODUCTION: The neural regulation of the microcirculation is done by the functional neurovascular unit that is composed of vascular, astroglial and neuronal cells. The neurovascular unit represents the interface between the Central Nervous System and the Vascular System. OBJECTIVE: This paper reviews the literature on functional neuroimaging with a particular focus on the mechanisms of the neurovascular coupling. CONCLUSIONS: Functional neuroimaging techniques as functional MRI, SPECT and PET distinguish metabolic and physiological processes underlying normal and abnormal events, based on neurovascular coupling. Although these techniques still have limitations in temporal and spatial resolution, they have considerably reduced the need for intracranial electrodes or invasive functional tests in the presurgical evaluation for intractable epilepsy. Recently, new techniques as optical approaches (measurement of intrinsic optical signals and near infrared spectroscopy) have increased both temporal and spatial resolutions. The use of such techniques in animal models has yielded experimental evidence for a neurovascular coupling in normal and epileptic conditions.

INTRODUÇÃO: A regulação da microcirculação cerebral é realizada pela unidade neurovascular, que é composta por vasos sangüíneos, células astrogliais e neuronais. A unidade neurovascular representa a interface funcional entre o Sistema Nervoso Central e o sistema vascular. OBJETIVO: Este trabalho revisa a literatura sobre técnicas de neuroimagem funcional com especial enfoque nos mecanismos do acoplamento neurovascular. CONCLUSÃO: Técnicas de neuroimagem como a Ressonância Magnética funcional, SPECT e PET baseiam-se no acoplamento neurovascular para explorarem os processos metabólicos e fisiológicos subjacentes a eventos cerebrais normais e anormais. Embora estas técnicas apresentem limitações de resolução temporal e espacial, sua aplicabilidade em epilepsia tem reduzido consideravelmente a necessidade de eletrodos intracranianos e de outros métodos funcionais invasivos na avaliação pré-cirúrgica de pacientes com epilepsia intratável. Recentemente, novos procedimentos ópticos (mensuração do sinal intrínseco óptico e espectroscopia por raio infravermelho) que possuem excelente resolução espacial e temporal têm fornecido evidências experimentais do acoplamento neurovascular no cérebro normal e epiléptico.