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-αand 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.

Plasma from healthy donors protects blood-brain barrier integrity via FGF21 and improves the recovery in a mouse model of cerebral ischaemia

Background Healthy plasma therapy reverses cognitive deficits and promotes neuroplasticity in ageing brain disease.However,whether healthy plasma therapy improve blood-brain barrier integrity after stroke remains unknown.Methods Here,we intravenously injected healthy female mouse plasma into adult female ischaemic stroke C57BL/6 mouse induced by 90 min transient middle cerebral artery occlusion for eight consecutive days.Infarct volume,brain atrophy and neurobehavioural tests were examined to assess the outcomes of plasma treatment.Cell apoptosis,blood-brain barrier integrity and fibroblast growth factor 21 knockout mice were used to explore the underlying mechanism.Results Plasma injection improved neurobehavioural recovery and decreased infarct volume,brain oedema and atrophy after stroke.Immunostaining showed that the number of transferase dUTP nick end labelling+/NeuN+cells decreased in the plasma-injected group.Meanwhile,plasma injection reduced ZO-1,occluding and claudin-5 tight junction gap formation and IgG extravasation at 3 days after ischaemic stroke.Western blot results showed that the FGF21 expression increased in the plasma-injected mice.However,using FGF21 knockout mouse plasma injecting to the ischaemic wild-type mice diminished the neuroprotective effects.Conclusions Our study demonstrated that healthy adult plasma treatment protected the structural and functional integrity of blood-brain barrier,reduced neuronal apoptosis and improved functional recovery via FGF21,opening a new avenue for ischaemic stroke therapy.