Time Course of Changes in the Neurovascular Unit after Hypoxic-Ischemic Injury in Neonatal Rats

Neurovascular protection of alisol A on cerebral ischemia mice through activating the AKT/GSK3β pathway

Alisol A, a triterpene isolated from Alisma Orientale, has been shown to exhibit anti-inflammatory effects and vascular protection. This study was designed to observe the effect of alisol A on cerebral ischemia (CI)-induced neurovascular dysfunction in the hippocampus and to further explore the potential mechanisms. The results showed that alisol A treatment improved the neurological deficits and cognitive impairment of CI mice. Alisol A reduced gliosis and improved neuronal/glial metabolism. Accordingly, alisol A inhibited inflammatory factors IL-6 and IL-1β induced by overactivation of astrocytes and microglia, thus protecting the neurovasculature. Furthermore, alisol A promoted the survival of neurons by decreasing the ratio of Bax/Bcl-2, and protected brain microvascular endothelial cells (BMECs) by upregulating the expression of ZO-1, Occludin and CD31. The phosphorylation of protein kinase B (AKT) and glycogen synthase kinase 3β (GSK3β) increased after treatment with alisol A. To explore the underlying mechanism, AKT was inhibited. As expected, the neurovascular protection of alisol A above was eliminated by AKT inhibition. The present study primarily suggested that alisol A could exert neurovascular protection in the hippocampus of CI mice by activating the AKT/GSK3β pathway and may potentially be used for the treatment of CI.

Brain organoids for hypoxic-ischemic studies: from bench to bedside

Our current knowledge regarding the development of the human brain mostly derives from experimental studies on non-human primates, sheep, and rodents. However, these studies may not completely simulate all the features of human brain development as a result of species differences and variations in pre- and postnatal brain maturation. Therefore, it is important to supplement the in vivo animal models to increase the possibility that preclinical studies have appropriate relevance for potential future human trials. Three-dimensional brain organoid culture technology could complement in vivo animal studies to enhance the translatability of the preclinical animal studies and the understanding of brain-related disorders. In this review, we focus on the development of a model of hypoxic-ischemic (HI) brain injury using human brain organoids to complement the translation from animal experiments to human pathophysiology. We also discuss how the development of these tools provides potential opportunities to study fundamental aspects of the pathophysiology of HI-related brain injury including differences in the responses between males and females.

Inter-Alpha Inhibitor Proteins Modify the Microvasculature after Exposure to Hypoxia-Ischemia and Hypoxia in Neonatal Rats

Microvasculature develops during early brain development. Hypoxia-ischemia (HI) and hypoxia (H) predispose to brain injury in neonates. Inter-alpha inhibitor proteins (IAIPs) attenuate injury to the neonatal brain after exposure to HI. However, the effects of IAIPs on the brain microvasculature after exposure to HI have not been examined in neonates. Postnatal day-7 rats were exposed to sham treatment or right carotid artery ligation and 8% oxygen for 90 min. HI comprises hypoxia (H) and ischemia to the right hemisphere (HI-right) and hypoxia to the whole body, including the left hemisphere (H-left). Human IAIPs (hIAIPs, 30 mg/kg) or placebo were injected immediately, 24 and 48 h after HI/H. The brains were analyzed 72 h after HI/H to determine the effects of hIAIPs on the microvasculature by laminin immunohistochemistry and calculation of (1) the percentage area stained by laminin, (2) cumulative microvessel length, and (3) density of tunneling nanotubes (TNTs), which are sensitive indicators of the earliest phases of neo-vascularization/collateralization. hIAIPs mainly affected the percent of the laminin-stained area after HI/H, cumulative vessel length after H but not HI, and TNT density in females but not males. hIAIPs modify the effects of HI/H on the microvasculature after brain injury in neonatal rats and exhibit sex-related differential effects. Our findings suggest that treatment with hIAIPs after exposure to H and HI in neonatal rats affects the laminin content of the vessel basal lamina and angiogenic responses in a sex-related fashion.

Potential pharmacological target of tight junctions to improve the BBB permeability in neonatal Hypoxic-Ischemic encephalopathy Diseases

Neonatal encephalopathy (NE) is a pathological condition that describes a neurocognitive malfunction in the newborn that arises from fetal, peripartum, or intrapartum events of multifactorial nature, having a poor prognosis and accounting for an incidence of 5-8 per 1000 live births. Neonatal hypoxic-ischemic encephalopathy (HIE) is one of the most studied paradigms of NE, caused by a scarce cerebral perfusion and oxygen supply during perinatal life. The cerebral hypoxic-ischemic insult promotes a loss of permeability of the blood-brain barrier (BBB), an essential structural intermediary of blood-brain communication. This permeability disruption is associated with an increase in inflammatory cytokines, an increase of adhesion molecules, and oxidative stress which disturb the tight junction (TJ) performance and enable transcytosis and paracellular leakage, ultimately leading to death from brain cells. In this context, TJs proteins are essential to preserving the barrier mechanical stability and signaling that modulates the brain-blood vessel multicellular domains, known as neurovascular units (NVU). Recent studies have proposed different strategies with neuroprotective effects that allow for maintaining or restoring the integrity and permeability of the BBB. This review identifies and discusses regulator mechanisms and novel aspects of TJs in the BBB disruption induced by cerebral hypoxic insults during the perinatal period, evaluating potential pharmacological strategies to safeguard BBB integrity.

The impairment of intramural periarterial drainage in brain after subarachnoid hemorrhage

Interstitial fluid (ISF) from brain drains along the basement membranes of capillaries and arteries as Intramural Periarterial Drainage (IPAD); failure of IPAD results in cerebral amyloid angiopathy (CAA). In this study, we test the hypothesis that IPAD fails after subarachnoid haemorrhage (SAH). The rat SAH model was established using endovascular perforation method. Fluorescence dyes with various molecular weights were injected into cisterna magna of rats, and the pattern of IPAD after SAH was detected using immunofluorescence staining, two-photon fluorescent microscope, transmission electron microscope and magnetic resonance imaging tracking techniques. Our results showed that fluorescence dyes entered the brain along a periarterial compartment and were cleared from brain along the basement membranes of the capillaries, with different patterns based on individual molecular weights. After SAH, there was significant impairment in the IPAD system: marked expansion of perivascular spaces, and ISF clearance rate was significantly decreased, associated with the apoptosis of endothelial cells, activation of astrocytes, over-expression of matrix metalloproteinase 9 and loss of collagen type IV. In conclusion, experimental SAH leads to a failure of IPAD, clinically significant for long term complications such as CAA, following SAH.

Early Rehabilitation Exercise after Stroke Improves Neurological Recovery through Enhancing Angiogenesis in Patients and Cerebral Ischemia Rat Model

Among cerebrovascular diseases, ischemic stroke is a leading cause of mortality and disability. Thrombolytic therapy with tissue plasminogen activator is the first choice for clinical treatment, but its use is limited due to the high requirements of patient characteristics. Therefore, the choice of neurological rehabilitation strategies after stroke is an important prevention and treatment strategy to promote the recovery of neurological function in patients. This study shows that rehabilitation exercise 24 h after stroke can significantly improve the neurological function (6.47 ± 1.589 vs. 3.21 ± 1.069 and 0.76 ± 0.852), exercise ability (15.68 ± 5.95 vs. 162.32 ± 9.286 and 91.18 ± 7.377), daily living ability (23.37 ± 5.196 vs. 66.95 ± 4.707 and 6.55 ± 2.873), and quality of life (114.39 ± 7.772 vs. 168.61 ± 6.323 and 215.95 ± 10.977) of patients after 1 month and 3 months, and its ability to promote rehabilitation is better than that of rehabilitation exercise administered to patients 72 h after stroke (p < 0.001). Animal experiments show that treadmill exercise 24 h after middle cerebral artery occlusion and reperfusion can inhibit neuronal apoptosis, reduce the volume of cerebral infarction on the third (15.04 ± 1.07% vs. 30.67 ± 3.06%) and fifth (8.33 ± 1.53% vs. 30.67 ± 3.06%) days, and promote the recovery of neurological function on the third (7.22 ± 1.478 vs. 8.28 ± 1.018) and fifth (4.44 ± 0.784 vs. 6.00 ± 0.767) days. Mechanistic studies have shown that treadmill exercise increases the density of microvessels, regulates angiogenesis, and promotes the recovery of nerve function by upregulating the expression of vascular endothelial growth factor and laminin. This study shows that rehabilitation exercise 24 h after stroke is conducive to promoting the recovery of patients’ neurological function, and provides a scientific reference for the clinical rehabilitation of stroke patients.