The Role Of Pericyte In Blood Brain Barrier Damage After Subarachnoid Hemorrhage

Introduction:Subarachnoid hemorrhage refers to blood enter into subarachnoid space from a ruptured vessel, which is a kind of hemorrhagic stroke. About 30% patients die before admission,50% of survivors suffer from cognitive deficit,psychological disorder,memory impairment, hemiplegic paralysis, and loss of self-care ability to work and life due to secondary brain injury. Despite decades of efforts, mechanism behind secondary brain injury has not been fully elucidated. Previous research mainly focus on cerebral vasospasm,but a recent multicenter, randomised, double-blind, placebo-controlled phase 3 trial clinical trial(CONSCIOUS-2 and CONSCIOUS-3) found Clazosentan, a selective endothelin-1 inhibitor, had no significant effect on reducing mortality and vasospasm-related morbidity or functional outcome. Gradually appeared evidence suggest that brain damage occur at the time of blood enter into subarachnoid space, neurons apoptosis, necroptosis, overexcited several minutes after occurrence of SAH .John H. Zhang proposed to define "early brain injury (EBI)"as brain injury in 72 hours post-SAH. Treatment targeting on early brain injury became promising to reduce mortality and improve neurological outcome. However,failures of thousands of clinical trials for simply targeting on neuroprotection, promote us to consider decreasing damage of cells around neuron. Cells including neurons, astrocytes,endotheliocytes, pericytes, microglia, and supporting matrix like basement membrane comprise the neurovascular network. While, blood brain barrier which composed of endothelial cells, pericytes, basement membrane and astrocyte endfeet, is an important unit of neurovascular network, both pre-clinical and clinical trials show neurological deficit after blood brain barrier damage, and improving neurological function by repair it, and pericytes play a controller role in this process. So cure on blood brain barrier maybe promising to reduce EBI.Based on previous work, this study mainly focus on blood brain barrier and pericyte.Observing the role blood brain barrier and pericyte after SAH, and provide evidence and new treatment for patient.Materials and methods:1. Vascular puncturation were used to perform mice SAH model.2. CD 147 small interfering RNA(siRNA) and CypA siRNA was intracerebroventricularly injected 48h before SAH. CypA was administrated intracerebroventricularly 24h post-SAH.SAH scores, neurological outcomes, brain water content, evans blue extravasation, immunofluorescence,western blot, ELISA, flow cytomertry, were employed to study mechanism of CypA and its receptor CD147.3. Cyclosporine was injected i.p. 15min after SAH, neurological score, brain water content, evans blue extravasation, basement membrane integrity valuated after SAH.4. Mortality, neurological score, P/F ratio, HE stain, immunofluorescence, western blot,were measured after SAH in PDGF-ret mice.Results:1. We found CypA and CD 147 increased in pericytes post SAH both in vivo and in vitro. Exogenous CypA aggravated neurological outcome, brain edema, BBB damage, basal membrane breakdown by increasing pericytes NF-?B nuclear translocation and MMP9 secretion. CypA siRNA, CD 147 siRNA and CypA koncout can reverse those phenomenon.2. Cyclosporine effectively reduce neurological dysfunction, brain edema, BBB permeability and basal membrane damage through inhibit NF-?B nuclear transition and MMP9 secretion and 15mg/ml cyclosporine maybe an optimal dosage.3 . Blood brain barrier and pericytes play an important in pathophysiology after SAH.By targeting pericytes and blood brain barrier can effectively improving neurological outcome, and translational study on neurovascular network may find out new treatments for SAH patients.4. The mortality of PDGFB-ret mice after subarachnoid hemorrhage 72h was significantly higher than that of the wild type, and more severe alveolar collapse, a decrease in P/F, reduce the expression of lung SPB, SPC were observed. PDGFB signal are involved in acute lung injury after subarachnoid hemorrhage.Conclusion:1. Expression of CypA and CD147in percytes increased at 24h SAH. Exogenous CypA can aggravate the injury of blood brain barrier and neurological function, the mechanism may be mediated by CD 147 receptor, NF-?B nuclear translocation and the secretion of MMP9 in pericytes which induce degradation of basal membrane damage and tight junction protein. CD 147 siRNA may reduce blood brain barrier damage after SAH and improve the prognosis of patient.2. 15mg/kg cyclosporine can reduce blood brain barrier damage after SAH, probably by reducing nuclear tanslocation of NF-?B and secretion of MMP9, cyclosporine is commonly used in clinical medicine, may translate into a reliable treatment of early brain injury after SAH.3. Neurovascular network especially pericytes play an important role in the brain microcirculation homeostasis and the process of wound repair. The treatment target pericytes and neurovascular network is likely to reduce damage of early brain injury, then improve the prognosis of the patients. Based on the study of pericytes in neurovascular network may provide effective methods for clinical translation and treatment of SAH.4. Aggravation lung injury increase the mortality of subarachnoid hemorrhage, the mechanism may include PDGFB, SPB, SPC. By reducing the lung injury after subarachnoid hemorrhage can lower the mortality of patients.