Simultaneous ischemic regions targeting and BBB crossing strategy to harness extracellular vesicles for therapeutic delivery in ischemic stroke.

Extracellular vesicles (EVs) derived from adipose-derived stem cells (ADSC-EVs) hold great promise for ischemic stroke treatment, but their therapeutic efficacy is greatly limited due to insufficient targeting ability. Previous reports focused on single ischemic targeting or blood-brain barrier (BBB) penetration, precise delivery to the brain parenchyma has not been fully considered. This study leveraged the targeting ability of RGD peptide and the cell penetrating ability of Angiopep-2 peptide to deliver ADSC-EVs precisely to the impaired brain parenchyma. We found that dual-modified EVs (RA-EVs) significantly enhanced the transcellular permeability across BBB in vitro, and not only targeted ischemic blood vessels but also achieved rapid accumulation in the ischemic lesion area after intravenous administration in vivo. RA-EVs further decreased the infarct volume, apoptosis, BBB disruption, and neurobehavioral deficits. RNA sequencing revealed the molecular regulation mechanism after administration. These findings demonstrate that dual-modification optimizes brain parenchymal targeting and highlights the significance of recruitment and penetration as a previously unidentified strategy for harnessing EVs for therapeutic delivery in ischemic stroke.

Microglia and astrocytes mediate synapse engulfment in a MER tyrosine kinase-dependent manner after traumatic brain injury.

Recent studies have shown that microglia/macrophages and astrocytes can mediate synaptic phagocytosis through the MER proto-oncokinase in developmental or stroke models, but it is unclear whether the same mechanism is also active in traumatic brain injury. In this study, we established a mouse model of traumatic brain injury and found that both microglia/macrophages and astrocytes phagocytosed synapses and expression of the MER proto-oncokinase increased 14 days after injury. Specific knockout of MER in microglia/macrophages or astrocytes markedly reduced injury volume and greatly improved neurobehavioral function. In addition, in both microglia/macrophages-specific and astrocytes-specific MER knock-out mice, the number of microglia/macrophage and astrocyte phagocytosing synapses was markedly decreased, and the total number of dendritic spines was increased. Our study suggested that MER proto-oncokinase expression in microglia/macrophages and astrocytes may play an important role in synaptic phagocytosis, and inhibiting this process could be a new strategy for treating traumatic brain injury.

Transcranial focused ultrasound stimulation reduces vasogenic edema after middle cerebral artery occlusion in mice.

Blood-brain barrier (BBB) disruption underlies the vasogenic edema and neuronal cell death induced by acute ischemic stroke. Reducing this disruption has therapeutic potential. Transcranial focused ultrasound stimulation has shown neuromodulatory and neuroprotective effects in various brain diseases including ischemic stroke. Ultrasound stimulation can reduce inflammation and promote angiogenesis and neural circuit remodeling. However, its effect on the BBB in the acute phase of ischemic stroke is unknown. In this study of mice subjected to middle cerebral artery occlusion for 90 minutes, low-intensity low-frequency (0.5 MHz) transcranial focused ultrasound stimulation was applied 2, 4, and 8 hours after occlusion. Ultrasound stimulation reduced edema volume, improved neurobehavioral outcomes, improved BBB integrity (enhanced tight junction protein ZO-1 expression and reduced IgG leakage), and reduced secretion of the inflammatory factors tumor necrosis factor-α and activation of matrix metalloproteinase-9 in the ischemic brain. Our results show that low-intensity ultrasound stimulation attenuated BBB disruption and edema formation, which suggests it may have therapeutic use in ischemic brain disease as a protector of BBB integrity.

Oligodendrocyte precursor cell transplantation promotes angiogenesis and remyelination via Wnt/ß-catenin pathway in a mouse model of middle cerebral artery occlusion.

White matter injury is a critical pathological characteristic during ischemic stroke. Oligodendrocyte precursor cells participate in white matter repairing and remodeling during ischemic brain injury. Since oligodendrocyte precursor cells could promote Wnt-dependent angiogenesis and migrate along vasculature for the myelination during the development in the central nervous system, we explore whether exogenous oligodendrocyte precursor cell transplantation promotes angiogenesis and remyelination after middle cerebral artery occlusion in mice. Here, oligodendrocyte precursor cell transplantation improved motor and cognitive function, and alleviated brain atrophy. Furthermore, oligodendrocyte precursor cell transplantation promoted functional angiogenesis, and increased myelin basic protein expression after ischemic stroke. The further study suggested that white matter repairing after oligodendrocyte precursor cell transplantation depended on angiogenesis induced by Wnt/ß-catenin signal pathway. Our results demonstrated a novel pathway that Wnt7a from oligodendrocyte precursor cells acting on endothelial ß-catenin promoted angiogenesis and improved neurobehavioral outcomes, which facilitated white matter repair and remodeling during ischemic stroke.

P2Y6 receptor inhibition aggravates ischemic brain injury by reducing microglial phagocytosis.

INTRODUCTION: Clearance of damaged cells and debris is beneficial for the functional recovery after ischemic brain injury. However, the specific phagocytic receptor that mediates microglial phagocytosis after ischemic stroke is unknown. AIM: To investigate whether P2Y6 receptor-mediated microglial phagocytosis is beneficial for the debris clearance and functional recovery after ischemic stroke. RESULTS: The expression of the P2Y6 receptor in microglia increased within 3 days after transient middle cerebral artery occlusion. Inhibition of microglial phagocytosis by the selective inhibitor MRS2578 enlarged the brain atrophy and edema volume after ischemic stroke, subsequently aggravated neurological function as measured by modified neurological severity scores and Grid walking test. MRS2578 treatment had no effect on the expression of IL-1α, IL-1ß, IL-6, IL-10, TNF-α, TGF-ß, and MPO after ischemic stroke. Finally, we found that the expression of myosin light chain kinase decreased after microglial phagocytosis inhibition in the ischemic mouse brain, which suggested that myosin light chain kinase was involved in P2Y6 receptor-mediated phagocytosis. CONCLUSION: Our results indicate that P2Y6 receptor-mediated microglial phagocytosis plays a beneficial role during the acute stage of ischemic stroke, which can be a therapeutic target for ischemic stroke.

L-glutamine protects mouse brain from ischemic injury via up-regulating heat shock protein 70.

INTRODUCTION: L-glutamine is an antioxidant that plays a role in a variety of biochemical processes. Given that oxidative stress is a key component of stroke pathology, the potential of L-glutamine in the treatment of ischemic stroke is worth exploring. AIMS: In this study, we investigated the effect and mechanisms of action of L-glutamine after cerebral ischemic injury. RESULTS: L-glutamine reduced brain infarct volume and promoted neurobehavioral recovery in mice. L-glutamine administration increased the expression of heat-shock protein 70 (HSP70) in astrocytes and endothelial cells. Such effects were abolished by the coadministration of Apoptozole, an inhibitor of the ATPase activity of HSP70. L-glutamine also reduced oxidative stress and neuronal apoptosis, and increased the level of superoxide dismutase, glutathione, and brain-derived neurotrophic factor. Cotreatment with Apoptozole abolished these effects. Cell culture study further revealed that the conditioned medium from astrocytes cultured with L-glutamine reduced the apoptosis of neurons after oxygen-glucose deprivation. CONCLUSION: L-glutamine attenuated ischemic brain injury and promoted functional recovery via HSP70, suggesting its potential in ischemic stroke therapy.

Dl-3-N-butylphthalide promotes angiogenesis and upregulates sonic hedgehog expression after cerebral ischemia in rats.

INTRODUCTION: Dl-3-N-butylphthalide (NBP), a small molecule drug used clinically in the acute phase of ischemic stroke, has been shown to improve functional recovery and promote angiogenesis and collateral vessel circulation after experimental cerebral ischemia. However, the underlying molecular mechanism is unknown. AIMS: To explore the potential molecular mechanism of angiogenesis induced by NBP after cerebral ischemia. RESULTS: NBP treatment attenuated body weight loss, reduced brain infarct volume, and improved neurobehavioral outcomes during focal ischemia compared to the control rats (P < 0.05). NBP increased the number of CD31+ microvessels, the number of CD31+ /BrdU+ proliferating endothelial cells, and the functional vascular density (P < 0.05). Further study demonstrated that NBP also promoted the expression of vascular endothelial growth factor and angiopoietin-1 (P < 0.05), which was accompanied by upregulated sonic hedgehog expression in astrocytes in vivo and in vitro. CONCLUSION: NBP treatment promoted the expression of vascular endothelial growth factor and angiopoietin-1, induced angiogenesis, and improved neurobehavioral recovery. These effects were associated with increased sonic hedgehog expression after NBP treatment. Our results broadened the clinical application of NBP to include the later phase of ischemia.

Opportunities and challenges: stem cell-based therapy for the treatment of ischemic stroke.

Stem cell-based therapy for ischemic stroke has been widely explored in animal models and provides strong evidence of benefits. In this review, we summarize the types of stem cells, various delivery routes, and tracking tools for stem cell therapy of ischemic stroke. MSCs, EPCs, and NSCs are the most explored cell types for ischemic stroke treatment. Although the mechanisms of stem cell-based therapies are not fully understood, the most possible functions of the transplanted cells are releasing growth factors and regulating microenvironment through paracrine mechanism. Clinical application of stem cell-based therapy is still in its infancy. The next decade of stem cell research in stroke field needs to focus on combining different stem cells and different imaging modalities to fully explore the potential of this therapeutic avenue: from bench to bedside and vice versa.

Postacute stromal cell-derived factor-1α expression promotes neurovascular recovery in ischemic mice.

BACKGROUND AND PURPOSE: Acute interventions of stroke are often challenged by a narrow treatment window. In this study, we explore treatments in the postacute phase of stroke with wider windows of opportunity. We investigated the effects of stromal cell-derived factor (SDF-1α) in neurovascular recovery during the postacute phase and downstream signaling pathways, underlying SDF-1α-mediated neurovascular recovery. METHODS: Adult male Institute of Cancer Research (ICR) mice underwent middle cerebral artery occlusion. One week after middle cerebral artery occlusion, the animals received stereotactic injection of adenoassociated virus (AAV) carrying SDF-1α gene as treatment or AAV-green fluorescent protein as control and were monitored for 5 weeks. Neurobehavioral outcomes were evaluated, and brain atrophy was measured. Neurogenesis and angiogenesis were examined. The proliferation and migration of neural progenitor cells were evaluated. Downstream pathways of SDF-1α were investigated. Inflammatory response was monitored. RESULTS: Neurobehavioral outcomes were improved, and brain atrophy was greatly reduced for ≤5 weeks in AAV-SDF-1α groups when compared with the control. SDF-1 receptor CXCR4 was upregulated and colocalized with neural and endothelial progenitor cells. The number of nestin(+) and doublecortin(+)/bromodeoxyuridine(+) cells in the subventricular zone, doublecortin(+) and neuron(+)/bromodeoxyuridine(+) cells in the perifocal region, and cluster of differentiation (CD)31(+) and bromodeoxyuridine(+)/CD31(+) microvessels are also significantly increased in AAV-SDF-1α groups. Administration of CXCR4 antagonist AMD3100 eliminated the beneficial effects of SDF-1α. SDF-1α/CXCR4 interaction activated AKT, extracellular signal-regulated kinases (ERK), and P38 mitogen-activated protein kinase (MAPK) signaling pathways but not the c-Jun N-terminal kinase (JNK) pathway. CONCLUSIONS: SDF-1α promoted neurogenesis and angiogenesis during the postacute phase of ischemia without eliciting an inflammatory response. AAV-SDF-1α expression represents a promising avenue for ischemic stroke therapy with a wider treatment window.

Overexpression of adiponectin improves neurobehavioral outcomes after focal cerebral ischemia in aged mice.

AIMS: To study whether adiponectin (APN) could improve neurological outcomes in aged mice after ischemic stroke. METHODS: Adeno-associated virus carrying APN gene was injected into aged and young adult mice 7 days before transient middle cerebral artery occlusion (tMCAO). Atrophic volumes and neurobehavioral deficiencies were determined up to 28 days after tMCAO. Focal angiogenesis was determined based on blood vessel number in the ischemic regions. RESULTS: Increased atrophic volume and more sever neurobehavioral deficits were found in the aged mice compared with young adult mice (P < 0.05). AAV-APN gene transfer attenuated atrophic volume and improved neurobehavioral outcomes, along with increased focal angiogenesis in both aged and young adult mice, compared with control animals (P < 0.05). In addition, the attenuation of atrophic volume and the improvement in neurobehavioral outcomes were much more significant in aged mice than in young adult mice after AAV-APN administration (P < 0.05). The number of microvessels in aged AAV-APN mouse ischemic brain was higher than in young adult AAV-APN treated mouse brain (P < 0.05). CONCLUSIONS: Our results demonstrate that APN overexpression reduces ischemic brain injury and improves neurobehavioral function recovery in aged mice than in young mice, suggesting APN is more beneficial in aged animals after ischemic stroke.