Classification, risk factors, and outcomes of patients with progressive hemorrhagic injury after traumatic brain injury.

BACKGROUND: According to the pathoanatomic classification system, progressive hemorrhagic injury (PHI) can be categorized into progressive intraparenchymal contusion or hematoma (pIPCH), epidural hematoma (pEDH), subdural hematoma (pSDH), and traumatic subarachnoid hemorrhage (ptSAH). The clinical features of each type differ greatly. The objective of this study was to determine the predictors, clinical management, and outcomes of PHI according to this classification. METHODS: Multivariate logistic regression analysis was used to identify independent risk factors for PHI and each subgroup. Patients with IPCH or EDH were selected for subgroup propensity score matching (PSM) to exclude confounding factors before evaluating the association of hematoma progression with the outcomes by classification. RESULTS: In the present cohort of 419 patients, 123 (29.4%) demonstrated PHI by serial CT scan. Of them, progressive ICPH (58.5%) was the most common type, followed by pEDH (28.5%), pSDH (9.8%), and ptSAH (3.2%). Old age (≥ 60 years), lower motor Glasgow Coma Scale score, larger primary lesion volume, and higher level of D-dimer were independent risk factors related to PHI. These factors were also independent predictors for pIPCH, but not for pEDH. The time to first CT scan and presence of skull linear fracture were robust risk factors for pEDH. After PSM, the 6-month mortality and unfavorable survival rates were significantly higher in the pIPCH group than the non-pIPCH group (24.2% vs. 1.8% and 12.1% vs. 7.3%, respectively, p < 0.001), but not significantly different between the pEDH group and the non-pEDH group. CONCLUSIONS: Understanding the specific patterns of PHI according to its classification can help early recognition and suggest targeted prevention or treatment strategies to improve patients' neurological outcomes.

MicroRNA-126-3p/-5p Overexpression Attenuates Blood-Brain Barrier Disruption in a Mouse Model of Middle Cerebral Artery Occlusion.

Background and Purpose- Blood-brain barrier (BBB) disruption is a critical pathological feature after stroke. MicroRNA-126 (miR-126) maintains BBB integrity by regulating endothelial cell function during development. However, the role of miR-126-3p and -5p in BBB integrity after stroke is unclear. Here, we investigated whether miR-126-3p and -5p overexpression regulates BBB integrity after cerebral ischemia. Methods- A lentivirus carrying genes encoding miR-126-3p or -5p was stereotactically injected into adult male Institute of Cancer Research mouse brains (n=36). Permanent middle cerebral artery occlusion was performed 2 weeks after virus injection. Brain infarct volume, edema volume, and modified neurological severity score were assessed at 1 and 3 days after ischemia. Immunostaining of ZO-1 (zonula occludens-1) and occludin was used to evaluate BBB integrity. IL-1ß (interleukin-1ß), TNF-α (tumor necrosis factor-α), VCAM-1 (vascular cell adhesion molecule-1), and E-selectin expression levels were determined by real-time polymerase chain reaction and Western blot analysis. Results- The expression of miR-126-3p and -5p decreased at 1 and 3 days after ischemia (P<0.05). Injection of lentiviral miR-126-3p or -5p reduced brain infarct volume and edema volume (P<0.05) and attenuated the decrease in ZO-1/occludin protein levels and IgG leakage at 3 days after stroke (P<0.05). Injection of lentiviral miR-126-5p improved behavioral outcomes at 3 days after stroke (P<0.05). miR-126-3p and -5p overexpression downregulated the expression of proinflammatory cytokines IL-1ß and TNF-α and adhesion molecules VCAM-1 and E-selectin, as well as decreased MPO+ (myeloperoxidase positive) cell numbers at 3 days after ischemia (P<0.05). Conclusions- miR-126-3p and -5p overexpression reduced the expression of proinflammatory cytokines and adhesion molecules, and attenuated BBB disruption after ischemic stroke, suggesting that miR-126-3p and -5p are new therapeutic targets in the acute stage of stroke.

Sesamin alleviates blood-brain barrier disruption in mice with experimental traumatic brain injury.

Sesamin, a major lignan of sesame oil, was reported to have neuroprotective effects in several brain injury models. However, its protective action in maintaining blood-brain barrier (BBB) integrity has not been studied. In this study we investigated the effects of sesamin on the BBB in a mouse model of traumatic brain injury (TBI) and explored the underlying mechanisms. Adult male C57BL/6 mice were subjected to a controlled cortical impact (CCI) injury and then received sesamin (30 mg·kg-1·d-1, ip). The mice were euthanized on the 1st and 3rd days after CCI injury and samples were collected for analysis. Sesamin treatment significantly attenuated CCI-induced brain edema on the 1st and 3rd days after the injury, evidenced by the decreases in water content, tissue hemoglobin levels, Evans blue extravasation and AQP4 expression levels in the ipsilateral cortical tissue compared with the vehicle-treated group. Furthermore, sesamin treatment significantly alleviated CCI-induced loss of the tight junction proteins ZO-1 and occludin in the brain tissues. The neuroprotective mechanisms of sesamin were further explored in cultured mouse brain microvascular bEnd.3 cells subjected to biaxial stretch injury (SI). Pretreatment with sesamin (50 µmol/L) significantly alleviated SI-induced loss of ZO-1 in bEnd.3 cells. Furthermore, we revealed that pretreatment with sesamin significantly attenuated SI-induced oxidative stress and early-stage apoptosis in bEnd.3 cells by decreasing the activation of ERK, p-38 and caspase-3. In conclusion, sesamin alleviates BBB disruption at least partly through its anti-oxidative and anti-apoptotic effects on endothelial cells in CCI injury. These findings suggest that sesamin may be a promising potential therapeutic intervention for preventing disruption of the BBB after TBI.

Predicting posttraumatic hydrocephalus: derivation and validation of a risk scoring system based on clinical characteristics.

Posttraumatic hydrocephalus (PTH) is a disorder of disturbed cerebrospinal fluid (CSF) dynamics after traumatic brain injury (TBI). It can lead to brain metabolic impairment and dysfunction and has a high risk of clinical deterioration and worse outcomes. The incidence and risk factors for the development of PTH after decompressive craniectomy (DC) has been assessed in previous studies, but rare studies identify patients with higher risk for PTH among all TBI patients. This study aimed to develop and validate a risk scoring system to predict PTH after TBI. Demographics, injury severity, duration of coma, radiologic findings, and DC were evaluated to determine the independent predictors of PTH during hospitalization until 6 months following TBI through logistic regression analysis. A risk stratification system was created by assigning a number of points for each predictor and validated in an independent cohort. The model accuracy was assessed by the area under the receiver operating characteristic curve (AUC). Of 526 patients in the derivation cohort, 57 (10.84%) developed PTH during 6 months follow up. Age > 50 yrs (Odd ratio [OR] = 1.91, 95% confidence interval [CI] 1.09-3.75, 4 points), duration of coma ≥1 w (OR = 5.68, 95% CI 2.57-13.47, 9 points), Fisher grade III (OR = 2.19, 95% CI 1.24-4.36, 5 points) or IV (OR = 3.87, 95% CI 1.93-8.43, 7 points), bilateral DC (OR = 6.13, 95% CI 2.82-18.14, 9 points), and extra herniation after DC (OR = 2.36, 95% CI 1.46-4.92, 5 points) were independently associated with PTH. Rates of PTH for the low- (0-12 points), intermediate- (13-22 points) and high-risk (23-34 points) groups were 1.16%, 35.19% and 78.57% (p < 0.0001). The corresponding rates in the validation cohort, where 17/175 (9.71%) developed PTH, were 1.35%, 37.50% and 81.82% (p < 0.0001). The risk score model exhibited good-excellent discrimination in both cohorts, with AUC of 0.839 versus 0.894 (derivation versus validation) and good calibration (Hosmer-Lemshow p = 0.56 versus 0.68). This model will be useful to identify patients at high risk for PTH who may be candidates for preventive interventions, and to improve their outcomes.

SIRT2 inhibition exacerbates neuroinflammation and blood-brain barrier disruption in experimental traumatic brain injury by enhancing NF-κB p65 acetylation and activation.

Sirtuin 2 (SIRT2) is a member of the sirtuin family of NAD(+) -dependent protein deacetylases. In recent years, SIRT2 inhibition has emerged as a promising treatment for neurodegenerative diseases. However, to date, there is no evidence of a specific role for SIRT2 in traumatic brain injury (TBI). We investigated the effects of SIRT2 inhibition on experimental TBI using the controlled cortical impact (CCI) injury model. Adult male mice underwent CCI or sham surgery. A selective brain-permeable SIRT2 inhibitor, AK-7, was administrated 30 min before injury. The volume of the brain edema lesion and the water content of the brain were significantly increased in mice treated with AK-7 (20 mg/kg), compared with the vehicle group, following TBI (p < 0.05 at 1 day and p < 0.05 at 3 days, respectively). Concomitantly, AK-7 administration greatly worsened neurobehavioral deficits on days 3 and 7 after CCI. Furthermore, blood-brain barrier disruption and matrix metalloproteinases (MMP)-9 activity increased following SIRT2 inhibition. AK-7 treatment increased TBI-induced microglial activation both in vivo and in vitro, accompanied by a large increase in the expression and release of inflammatory cytokines. Mechanistically, SIRT2 inhibition increased both K310 acetylation and nuclear translocation of NF-κB p65, leading to enhanced NF-κB activation and up-regulation of its target genes, including aquaporin 4 (AQP4), MMP-9, and pro-inflammatory cytokines. Together, these data demonstrate that SIRT2 inhibition exacerbates TBI by increasing NF-κB p65 acetylation and activation. Our findings provide additional evidence of an anti-inflammatory effect of SIRT2. SIRT2 is a member of the sirtuin family of NAD+-dependent protein deacetylases. Our study suggests that the SIRT2 inhibitor AK-7 exacerbates traumatic brain injury (TBI) via a potential mechanism involving increased acetylation and nuclear translocation of NF-κB p65, resulting in up-regulation of NF-κB target genes, including aquaporin 4 (AQP4), matrix metalloproteinase 9 (MMP-9), and pro-inflammatory cytokines. Our findings provide additional evidence of an anti-inflammatory effect of SIRT2.

Relationship between trauma-induced coagulopathy and progressive hemorrhagic injury in patients with traumatic brain injury.

Progressive hemorrhagic injury (PHI) can be divided into coagulopathy-related PHI and normal coagu- lation PHI. Coagulation disorders after traumatic brain injuries can be included in trauma-induced coagulopathy (TIC). Some studies showed that TIC is associated with PHI and increases the rates of disability and mortality. In this review, we discussed some mechanisms in TIC, which is of great importance in the development of PHI, including tissue factor (TF) hypothesis, protein C pathway and thrombocytopenia. The main mechanism in the relation of TIC to PHI is hypocoagulability. We also reviewed some coagulopathy parameters and proposed some possible risk factors, predictors and therapies.

Endogenous TGFß1 Plays a Crucial Role in Functional Recovery After Traumatic Brain Injury Associated with Smad3 Signal in Rats.

Transforming growth factor-ß 1 (TGFß1) has a diverse role in astrogliosis and neuronal survival, but the underlying mechanism remains to be elucidated, especially in traumatic brain injury (TBI). Here, we show that the expression of TGFß1 was increased in the pericontusional region, accompanied with astrogliosis and neuronal loss in TBI rats. Moreover, TGFß1 knockdown not only reduced the number of neurons and inhibited astrogliosis but also resulted in a significant neurological dysfunction in rats with TBI. Subsequently, Smad3, a key downstream signal of TGFß1, was involved in pericontusional region after TBI. These findings therefore indicate that TGFß1 is involved in neuroprotection and astrogliosis, via activation of down stream Smad3 signal in the brain after injury.

Neuroglobin and Nogo-a as biomarkers for the severity and prognosis of traumatic brain injury.

OBJECTIVE: To identify the early changes of serum neuroglobin and Nogo-A concentrations and the relations to traumatic brain injury (TBI) severity and prognosis. METHODS: Serum samples were obtained and analyzed from 34 patients with TBI within the first 96 h after injury. Comparative analysis combined with Glasgow Coma Scale (GCS) scores and the 6-month prognosis of these patients was performed. RESULTS: Significant correlations were found between peak serum neuroglobin and Nogo-A concentrations and a patient's GCS score on admission (p < 0.001). The mean peak serum neuroglobin and Nogo-A concentrations were both significantly higher in patients with an unfavorable outcome at 6 months after injury (p < 0.05). CONCLUSIONS: Serum neuroglobin and Nogo-A levels could be suggested as biomarkers for predicting TBI severity and prognosis.

Quantitative assessment of the association between XRCC3 C18607T polymorphism and glioma risk.

XRCC3 has an important function in the DNA double-strand break, and XRCC3 C18607T polymorphism is a common polymorphism at exon 7 of the XRCC3 gene. Published data on the association between XRCC3 C18607T polymorphism and glioma risk were inconclusive. Electronic databases of PubMed, and Embase were searched for studies assessing the association between XRCC3 C18607T polymorphism and glioma risk. Pooled odds ratio (OR) and 95 % confidence interval (95 % CI) were calculated to estimate the association. Ten studies with five studies from Caucasians and five studies from Asians were included, including 9,369 subjects. Meta-analysis of total included studies showed that XRCC3 C18607T polymorphism was associated with increased risk of glioma (T vs. C: OR = 1.14, 95 % CI 1.02-1.28, P = 0.02; TT vs. CC: OR = 1.37, 95 % CI 1.03-1.83, P = 0.03; TT vs. CC/CT: OR = 1.31, 95 % CI 1.00-1.71, P = 0.05; TT/CT vs. CC: OR = 1.12, 95 % CI 1.02-1.22, P = 0.02). Meta-analysis of the five studies from Asians showed that XRCC3 C18607T polymorphism was associated with increased risk of glioma (T vs. C: OR = 1.22, 95% CI 1.09-1.36, P < 0.01; TT vs. CC: OR = 1.89, 95 % CI 1.38-2.57, P < 0.01; TT vs. CC/CT: OR = 1.78, 95 % CI 1.31-2.40, P < 0.01; TT/CT vs. CC: OR = 1.19, 95 % CI 1.04-1.36, P = 0.01). Meta-analysis of the five studies from Caucasians didn't find the association. In conclusion, the finding from the meta-analysis provides strong evidence for the association between XRCC3 C18607T polymorphism and glioma risk.

Transplantation of astrocyte-derived mitochondria into injured astrocytes has a protective effect following stretch injury.

Traumatic brain injury (TBI) is a global public-health problem. Astrocytes, and their mitochondria, are important factors in the pathogenesis of TBI-induced secondary injury. Mitochondria extracted from healthy tissues and then transplanted have shown promise in models of a variety of diseases. However, the effect on recipient astrocytes is unclear. Here, we isolated primary astrocytes from newborn C57BL/6 mice, one portion of which was used to isolate mitochondria, and another was subjected to stretch injury (SI) followed by transplantation of the isolated mitochondria. After incubation for 12 h, cell viability, mitochondrial dysfunction, calcium overload, redox stress, inflammatory response, and apoptosis were improved. Live-cell imaging showed that the transplanted mitochondria were incorporated into injured astrocytes and fused with their mitochondrial networks, which was in accordance with the changes in the expression levels of markers of mitochondrial dynamics. The astrocytic IKK/NF-κB pathway was decelerated whereas the AMPK/PGC-1α pathway was accelerated by transplantation. Together, these results indicate that exogenous mitochondria from untreated astrocytes can be incorporated into injured astrocytes and fuse with their mitochondrial networks, improving cell viability by ameliorating mitochondrial dysfunction, redox stress, calcium overload, and inflammation.

Dose-dependent protective effect of bisperoxovanadium against acute cerebral ischemia in a rat model of ischemia/reperfusion injury.

PTEN (phosphatase and tensin homologue deleted on chromosome 10) is a dual-specificity lipid and protein phosphatase. The loss of PTEN was originally discovered in numerous human cancers. PTEN inhibition by bisperoxovanadium (bpV) reduces neurological damage after ischemic brain injury. The purpose of this study was to identify the optimal neuroprotective dose of bpV when administrated after focal ischemia/reperfusion (I/R) injury in rats. Focal I/R injury was induced using the middle cerebral artery occlusion method. bpV at doses of 0.25, 0.50 and 1.0 mg/kg were injected intraperitoneally just after reperfusion, with saline serving as a vehicle control. A maximal reduction in brain injury was observed with 1.0 mg/kg bpV. This dose of bpV also significantly blocked apoptosis in the penumbral cortex of rats. This beneficial effect was associated with the increasing levels of Akt phosphorylation in the penumbral cortex. These results demonstrate that the pharmacological inhibition of PTEN protects against I/R injury in a dose-dependent manner and the protective effect might be induced through upregulation of the phosphoinositide-3 kinase/Akt pro-survival pathway, suggesting a new therapeutic strategy to combat ischemic brain injury.

Knockout of Sirt2 alleviates traumatic brain injury in mice.

Sirtuin 2 (SIRT2) inhibition or Sirt2 knockout in animal models protects against the development of neurodegenerative diseases and cerebral ischemia. However, the role of SIRT2 in traumatic brain injury (TBI) remains unclear. In this study, we found that knockout of Sirt2 in a mouse model of TBI reduced brain edema, attenuated disruption of the blood-brain barrier, decreased expression of the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome, reduced the activity of the effector caspase-1, reduced neuroinflammation and neuronal pyroptosis, and improved neurological function. Knockout of Sirt2 in a mechanical stretch injury cell model in vitro also decreased expression of the NLRP3 inflammasome and pyroptosis. Our findings suggest that knockout of Sirt2 is neuroprotective against TBI; therefore, Sirt2 could be a novel target for TBI treatment.

Progranulin released from microglial lysosomes reduces neuronal ferroptosis after cerebral ischemia in mice.

The cellular redox state is essential for inhibiting ferroptosis. Progranulin (PGRN) plays an important role in maintaining the cellular redox state after ischemic brain injury. However, the effect of PGRN on ferroptosis and its underlying mechanism after cerebral ischemia remains unclear. This study assesses whether PGRN affects ferroptosis and explores its mechanism of action on ferroptosis after cerebral ischemia. We found endogenous PGRN expression in microglia increased on day 3 after ischemia. In addition, PGRN agonists chloroquine and trehalose upregulated PGRN expression, reduced brain infarct volume, and improved neurobehavioral outcomes after cerebral ischemia compared to controls (p < 0.05). Moreover, PGRN upregulation attenuated ferroptosis by decreasing malondialdehyde and increasing Gpx4, Nrf2, and Slc7a11 expression and glutathione content (p < 0.05). Furthermore, chloroquine induced microglial lysosome PGRN release, which was associated with increased neuron survival. Our results indicate that PGRN derived from microglial lysosomes effectively inhibits ferroptosis during ischemic brain injury, identifying it as a promising target for ischemic stroke therapy.

Inhibiting phosphatase and actin regulator 1 expression is neuroprotective in the context of traumatic brain injury.

Studies have found that the phosphatase actin regulatory factor 1 expression can be related to stroke, but it remains unclear whether changes in phosphatase actin regulatory factor 1 expression also play a role in traumatic brain injury. In this study we found that, in a mouse model of traumatic brain injury induced by controlled cortical impact, phosphatase actin regulatory factor 1 expression is increased in endothelial cells, neurons, astrocytes, and microglia. When we overexpressed phosphatase actin regulatory factor 1 by injection an adeno-associated virus vector into the contused area in the traumatic brain injury mice, the water content of the brain tissue increased. However, when phosphatase actin regulatory factor 1 was knocked down, the water content decreased. We also found that inhibiting phosphatase actin regulatory factor 1 expression regulated the nuclear factor kappa B signaling pathway, decreased blood-brain barrier permeability, reduced aquaporin 4 and intercellular adhesion molecule 1 expression, inhibited neuroinflammation, and neuronal apoptosis, thereby improving neurological function. The findings from this study indicate that phosphatase actin regulatory factor 1 may be a potential therapeutic target for traumatic brain injury.

Optogenetic Activation of Astrocytes Reduces Blood-Brain Barrier Disruption via IL-10 In Stroke.

Optogenetics has been used to regulate astrocyte activity and modulate neuronal function after brain injury. Activated astrocytes regulate blood-brain barrier functions and are thereby involved in brain repair. However, the effect and molecular mechanism of optogenetic-activated astrocytes on the change in barrier function in ischemic stroke remain obscure. In this study, adult male GFAP-ChR2-EYFP transgenic Sprague-Dawley rats were stimulated by optogenetics at 24, 36, 48, and 60 h after photothrombotic stroke to activate ipsilateral cortical astrocytes. The effects of activated astrocytes on barrier integrity and the underlying mechanisms were explored using immunostaining, western blotting, RT-qPCR, and shRNA interference. Neurobehavioral tests were performed to evaluate therapeutic efficacy. The results demonstrated that IgG leakage, gap formation of tight junction proteins, and matrix metallopeptidase 2 expression were reduced after optogenetic activation of astrocytes (p<0.05). Moreover, photo-stimulation of astrocytes protected neurons against apoptosis and improved neurobehavioral outcomes in stroke rats compared to controls (p<0.05). Notably, interleukin-10 expression in optogenetic-activated astrocytes significantly increased after ischemic stroke in rats. Inhibition of interleukin-10 in astrocytes compromised the protective effects of optogenetic-activated astrocytes (p<0.05). We found for the first time that interleukin-10 derived from optogenetic-activated astrocytes protected blood-brain barrier integrity by decreasing the activity of matrix metallopeptidase 2 and attenuated neuronal apoptosis, which provided a novel therapeutic approach and target in the acute stage of ischemic stroke.

A prospective clinical study of routine repeat computed tomography (CT) after traumatic brain injury (TBI).

PURPOSE: To discuss the repeated CT scanning in patients with traumatic brain injury (TBI) and to identify the conditions under which this approach is necessary. METHODS: One hundred and seventy-one patients who suffered TBI but were not surgically treated were divided into two groups: the routine-repeat CT group (n = 89) and the non-routine-repeat CT group (n = 82). The patients' clinical characteristics were compared. T-tests and stepwise logistic regression were used for analysis. Patients in the routine-repeat CT group were divided into three groups according to GCS scores to determine the need for routinely repeated CT scans. RESULTS: The results revealed statistically significant differences between the two groups in terms of neuro-ICU-LOS and LOS (p < 0.01). No significant differences emerged with respect to hospital charges and GCS scores at discharge (p > 0.05). AGE, international normalized ratio (INR), D-dimer concentration (DD), GCS scores and number of hours between the first CT scan and the injury (HCT1) were influential factors of developing progressive haemorrhage. CONCLUSION: The routine-repeat CT group fared better than did the non-routine-repeat CT group. Routinely repeated CTs were minimally effective among those with mild TBI, whereas this procedure demonstrated a significant effect on patients with moderate and severe TBI.

Cell cycle exit and neuronal differentiation 1-engineered embryonic neural stem cells enhance neuronal differentiation and neurobehavioral recovery after experimental traumatic brain injury.

Our previous study showed that cell cycle exit and neuronal differentiation 1 (CEND1) may participate in neural stem cell cycle exit and oriented differentiation. However, whether CEND1-transfected neural stem cells can improve the prognosis of traumatic brain injury remained unclear. In this study, we performed quantitative proteomic analysis and found that after traumatic brain injury, CEND1 expression was downregulated in mouse brain tissue. Three days after traumatic brain injury, we transplanted CEND1-transfected neural stem cells into the area surrounding the injury site. We found that at 5 weeks after traumatic brain injury, transplantation of CEND1-transfected neural stem cells markedly alleviated brain atrophy and greatly improved neurological function. In vivo and in vitro results indicate that CEND1 overexpression inhibited the proliferation of neural stem cells, but significantly promoted their neuronal differentiation. Additionally, CEND1 overexpression reduced protein levels of Notch1 and cyclin D1, but increased levels of p21 in CEND1-transfected neural stem cells. Treatment with CEND1-transfected neural stem cells was superior to similar treatment without CEND1 transfection. These findings suggest that transplantation of CEND1-transfected neural stem cells is a promising cell therapy for traumatic brain injury. This study was approved by the Animal Ethics Committee of the School of Biomedical Engineering of Shanghai Jiao Tong University, China (approval No. 2016034) on November 25, 2016.

Urolithin A alleviates blood-brain barrier disruption and attenuates neuronal apoptosis following traumatic brain injury in mice.

Urolithin A (UA) is a natural metabolite produced from polyphenolics in foods such as pomegranates, berries, and nuts. UA is neuroprotective against Parkinson's disease, Alzheimer's disease, and cerebral hemorrhage. However, its effect against traumatic brain injury remains unknown. In this study, we established adult C57BL/6J mouse models of traumatic brain injury by controlled cortical impact and then intraperitoneally administered UA. We found that UA greatly reduced brain edema; increased the expression of tight junction proteins in injured cortex; increased the immunopositivity of two neuronal autophagy markers, microtubule-associated protein 1A/B light chain 3A/B (LC3) and p62; downregulated protein kinase B (Akt) and mammalian target of rapamycin (mTOR), two regulators of the phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR signaling pathway; decreased the phosphorylation levels of inhibitor of NFκB (IκB) kinase alpha (IKKα) and nuclear factor kappa B (NFκB), two regulators of the neuroinflammation-related Akt/IKK/NFκB signaling pathway; reduced blood-brain barrier permeability and neuronal apoptosis in injured cortex; and improved mouse neurological function. These findings suggest that UA may be a candidate drug for the treatment of traumatic brain injury, and its neuroprotective effects may be mediated by inhibition of the PI3K/Akt/mTOR and Akt/IKK/NFκB signaling pathways, thus reducing neuroinflammation and enhancing autophagy.

M2 microglial small extracellular vesicles reduce glial scar formation via the miR-124/STAT3 pathway after ischemic stroke in mice.

Rationale: Glial scars present a major obstacle for neuronal regeneration after stroke. Thus, approaches to promote their degradation and inhibit their formation are beneficial for stroke recovery. The interaction of microglia and astrocytes is known to be involved in glial scar formation after stroke; however, how microglia affect glial scar formation remains unclear. Methods: Mice were treated daily with M2 microglial small extracellular vesicles through tail intravenous injections from day 1 to day 7 after middle cerebral artery occlusion. Glial scar, infarct volume, neurological score were detected after ischemia. microRNA and related protein were examined in peri-infarct areas of the brain following ischemia. Results: M2 microglial small extracellular vesicles reduced glial scar formation and promoted recovery after stroke and were enriched in miR-124. Furthermore, M2 microglial small extracellular vesicle treatment decreased the expression of the astrocyte proliferation gene signal transducer and activator of transcription 3, one of the targets of miR-124, and glial fibrillary acidic protein and inhibited astrocyte proliferation both in vitro and in vivo. It also decreased Notch 1 expression and increased Sox2 expression in astrocytes, which suggested that astrocytes had transformed into neuronal progenitor cells. Finally, miR-124 knockdown in M2 microglial small extracellular vesicles blocked their effects on glial scars and stroke recovery. Conclusions: Our results showed, for the first time, that microglia regulate glial scar formation via small extracellular vesicles, indicating that M2 microglial small extracellular vesicles could represent a new therapeutic approach for stroke.