Neurovascular Unit-Derived Extracellular Vesicles: From Their Physiopathological Roles to Their Clinical Applications in Acute Brain Injuries

Small Extracellular Vesicles From Hypoxia-Neuron Maintain Blood-Brain Barrier Integrity

BACKGROUND

Acute ischemic stroke disrupts communication between neurons and blood vessels in penumbral areas. How neurons and blood vessels cooperate to achieve blood-brain barrier repair remains unclear. Here, we reveal crosstalk between ischemic penumbral neurons and endothelial cells (ECs) mediated by circular RNA originating from oxoglutarate dehydrogenase (CircOGDH).

METHODS

We analyzed clinical data from patients with acute ischemic stroke to explore the relationship between CircOGDH levels and hemorrhagic transformation events. In addition, a middle cerebral artery occlusion and reperfusion mouse model with neuronal CircOGDH suppression was used to assess endothelial permeability. ECs with increased CircOGDH expression were analyzed for changes in COL4A4 (collagen type IV alpha 4) levels, and in vitro coculture experiments were conducted to examine small extracellular vesicle-mediated CircOGDH transfer between neurons and ECs.

RESULTS

Clinical data indicated that reduced CircOGDH levels were correlated with increased hemorrhagic transformation in patients with acute ischemic stroke. In the middle cerebral artery occlusion and reperfusion model, neuronal CircOGDH suppression impaired the restoration of endothelial permeability. ECs with increased CircOGDH expression exhibited higher COL4A4 levels, which helped maintain vascular stability. In vitro, hypoxic neurons transferred CircOGDH to ECs via small extracellular vesicles, leading to elevated COL4A4 expression and enhanced endothelial integrity.

CONCLUSIONS

Our findings highlight the significance of CircOGDH in neuron-EC crosstalk via small extracellular vesicles in the ischemic penumbra, emphasizing the need for balanced intervention strategies in acute ischemic stroke management.

Alzheimer's, Parkinson's, Frontotemporal Lobar Degeneration, and Amyotrophic Lateral Sclerosis Start in Pediatric Ages: Ultrafine Particulate Matter and Industrial Nanoparticles Are Key in the Early-Onset Neurodegeneration: Time to Invest in Preventive Medicine

Billions of people are exposed to fine particulate matter (PM2.5) levels above the USEPA's annual standard of 9 μg/m3. Common emission sources are anthropogenic, producing complex aerosolized toxins. Ultrafine particulate matter (UFPM) and industrial nanoparticles (NPs) have major detrimental effects on the brain, but the USA does not measure UFPM on a routine basis. This review focuses on the development and progression of common neurodegenerative diseases, as diagnosed through neuropathology, among young residents in Metropolitan Mexico City (MMC). MMC is one of the most polluted megacities in the world, with a population of 22 million residents, many of whom are unaware of the brain effects caused by their polluted atmosphere. Fatal neurodegenerative diseases (such as Alzheimer's and Parkinson's) that begin in childhood in populations living in air polluted environments are preventable. We conclude that UFPM/NPs are capable of disrupting neural homeostasis and give rise to relentless neurodegenerative processes throughout the entire life of the highly exposed population in MMC. The paradigm of reaching old age to have neurodegeneration is no longer supported. Neurodegenerative changes start early in pediatric ages and are irreversible. It is time to invest in preventive medicine.

Molecular Pathogenesis of Ischemic and Hemorrhagic Strokes: Background and Therapeutic Approaches

Stroke represents one of the neurological diseases most responsible for death and permanent disability in the world. Different factors, such as thrombus, emboli and atherosclerosis, take part in the intricate pathophysiology of stroke. Comprehending the molecular processes involved in this mechanism is crucial to developing new, specific and efficient treatments. Some common mechanisms are excitotoxicity and calcium overload, oxidative stress and neuroinflammation. Furthermore, non-coding RNAs (ncRNAs) are critical in pathophysiology and recovery after cerebral ischemia. ncRNAs, particularly microRNAs, and long non-coding RNAs (lncRNAs) are essential for angiogenesis and neuroprotection, and they have been suggested to be therapeutic, diagnostic and prognostic tools in cerebrovascular diseases, including stroke. This review summarizes the intricate molecular mechanisms underlying ischemic and hemorrhagic stroke and delves into the function of miRNAs in the development of brain damage. Furthermore, we will analyze new perspectives on treatment based on molecular mechanisms in addition to traditional stroke therapies.

Unraveling the Emerging Niche Role of Extracellular Vesicles (EVs) in Traumatic Brain Injury (TBI)

Extracellular vesicles or exosomes, often known as EVs, have acquired significant attention in the investigations of traumatic brain injury (TBI) and have a distinct advantage in actively researching the fundamental mechanisms underlying various clinical symptoms and diagnosing the wide range of traumatic brain injury cases. The mesenchymal stem cells (MSCs) can produce and release exosomes, which offer therapeutic benefits. Exosomes are tiny membranous vesicles produced by various cellular entities originating from endosomes. Several studies have reported that administering MSC-derived exosomes through intravenous infusions improves neurological recovery and promotes neuroplasticity in rats with traumatic brain damage. The therapeutic advantages of exosomes can be attributed to the microRNAs (miRNAs), which are small non-coding regulatory RNAs that significantly impact the regulation of posttranscriptional genes. Exosome-based therapies, which do not involve cells, have lately gained interest as a potential breakthrough in enhancing neuroplasticity and accelerating neurological recovery for various brain injuries and neurodegenerative diseases. This article explores the benefits and drawbacks of exosome treatment for traumatic brain injury while emphasizing the latest advancements in this field with clinical significance.

Exosomal miRNAs as Biomarkers of Ischemic Stroke

Exosomes are small lipid bilayer membrane particles released from all living cells into the extracellular environment. They carry several molecules and have a critical role in cell-cell communication under physiological and pathological conditions. In recent decades, exosomes, and especially their cargo, have emerged as a promising tool for several clinical conditions. However, the literature has become increasingly unambiguous in defining the role of exosomes in chronic cerebrovascular diseases. Because they can pass through the blood-brain barrier, they have great potential to reflect intracerebral changes. They can, thus, provide valuable insight into the mechanisms of central nervous system diseases. The purpose of this review is to describe the literature on the role of exosomal miRNA, which represents the most widely investigated exosomal biomarker, in strokes. First, we provide an overview of exosomes, from biology to isolation and characterization. Then, we describe the relationship between exosomes and stroke pathogenesis. Finally, we summarize the human studies evaluating exosomal miRNA biomarkers of stroke. Although the collective literature supports the potential use of exosomal miRNA as biomarkers of ischemic stroke, there are still several limitations hampering their introduction into clinical practice.

Immune regulation in neurovascular units after traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Survivors may experience movement disorders, memory loss, and cognitive deficits. However, there is a lack of understanding of the pathophysiology of TBI-mediated neuroinflammation and neurodegeneration. The immune regulation process of TBI involves changes in the peripheral and central nervous system (CNS) immunity, and intracranial blood vessels are essential communication centers. The neurovascular unit (NVU) is responsible for coupling blood flow with brain activity, and comprises endothelial cells, pericytes, astrocyte end-feet, and vast regulatory nerve terminals. A stable NVU is the basis for normal brain function. The concept of the NVU emphasizes that cell-cell interactions between different types of cells are essential for maintaining brain homeostasis. Previous studies have explored the effects of immune system changes after TBI. The NVU can help us further understand the immune regulation process. Herein, we enumerate the paradoxes of primary immune activation and chronic immunosuppression. We describe the changes in immune cells, cytokines/chemokines, and neuroinflammation after TBI. The post-immunomodulatory changes in NVU components are discussed, and research exploring immune changes in the NVU pattern is also described. Finally, we summarize immune regulation therapies and drugs after TBI. Therapies and drugs that focus on immune regulation have shown great potential for neuroprotection. These findings will help us further understand the pathological processes after TBI.