Vascular repair extends therapeutic window for ischemic stroke

 描述（申请人提供）：平均每40秒就有一名美国人中风，每4分钟就有一人死亡。在不同类型的中风中，急性缺血性中风是最常见的，成功治疗这种疾病仍然非常具有挑战性。“凝块破坏”药物组织纤溶酶原激活剂（tPA）是唯一批准用于急性缺血性中风临床使用的药物。然而，药物必须在中风发作后4.5小时内开始，否则会产生有害的副作用，包括脑内出血性转化（HT）。因此，重要的临床问题是开发将延长tPA的有限治疗时间窗或减少与tPA的延迟治疗相关的并发症的方法。粒细胞集落刺激因子（G-CSF）已被证明在缺血的动物模型中发挥神经保护作用。目前尚不清楚该药物是否可以减轻缺血性卒中中延迟tPA治疗的有害副作用。此外，我们在大鼠创伤性脑损伤（TBI）模型中发现，G-CSF单药治疗可减少灰质和白色区的神经炎症，并改善TBI诱导的内源性神经发生障碍。这些发现与所报道的G-CSF在缺血动物模型中的神经保护作用一起使我们假设G-CSF的治疗也将减少与tPA的延迟治疗相关的HT（目的1）。用G-CSF治疗将细胞从骨髓动员到外周血，包括含有内皮祖细胞（EPC）的CD 34+骨髓干细胞。几项研究表明，G-CSF在卒中中的有益作用（例如血管生成、血管发生等）由EPCs介导。此外，在以前的研究中，我们也表明，移植人脑内皮细胞通过增强血管生成来减轻大鼠中风引起的运动和神经功能缺损。根据这些发现，我们假设G-CSF在中风中tPA诱导的HT的情况下动员EPCs，并且EPCs通过增强血管发生或血管生成来减弱HT，这是保护血管系统的过程（目的2）。延迟的tPA诱导的HT已归因于tPA对神经血管单元的影响，并且还通过破坏血脑屏障（BBB）。我们假设G-CSF神经保护作用的另一个机制是通过募集的EPCs的血管生成和血管生成作用来保护BBB的完整性。本研究的长期目标是证明G-CSF联合tPA将减少迟发性tPA相关并发症，并延长tPA的溶栓疗效。总体影响是，在本研究完成时，这项工作的结果将为G-CSF减轻与tPA延迟治疗相关的HT的临床评价奠定基础。

 DESCRIPTION (provided by applicant): On average, one American has stroke every 40 seconds, and one dies every 4 minutes. Of the different types of stroke, acute ischemic stroke is the most common, and successful treatment of this medical condition remains very challenging. The "clot busting" drug tissue plasminogen activator (tPA) is the only drug approved for clinical use for acute ischemic stroke. However the drug must be initiated within 4.5 h of stroke onset or risk detrimental side effects including intracerebral hemorrhagic transformation (HT). Therefore, an important clinical problem is to develop methods that will extend the limited therapeutic time window of tPA or reduce complications associated with delayed treatment of tPA. The granulocyte-colony stimulating factor (G-CSF) has been shown to exert neuroprotective effects in animal models of ischemia. It is not yet known if the drug could attenuate detrimental side effects of delayed tPA treatment in ischemic stroke. Furthermore, we have shown in a rat model of traumatic brain injury (TBI) that G-CSF monotherapy reduced neuroinflammation in the gray and white matter areas and also ameliorated TBI-induced impairment in endogenous neurogenesis. These findings taken together with reported neuroprotective effects of G-CSF in animal models of ischemia led us to hypothesize that the treatment of G-CSF will also reduce HT associated with delayed treatment of tPA (Aim 1). Treatment with G-CSF mobilizes cells from the bone marrow to the peripheral blood including CD34+ bone marrow stem cells which contain endothelial progenitor cells (EPCs). Several studies suggested that beneficial effects of G-CSF in stroke (e.g. angiogenesis, vasculogenesis, etc.) are mediated by EPCs. Moreover, in a previous study, we have also shown that transplantation of human cerebral endothelial cells attenuated stroke-induced motor and neurological deficits in rats via enhancement of vasculogenesis. In light of these findings, we hypothesized that G-CSF mobilizes EPCs in the setting of tPA-induced HT in stroke, and EPCs attenuate HT via enhancement of vasculogenesis or angiogenesis, processes that preserve the cerebrovasculature (Aim 2). Delayed tPA-induced HT has been attributed to effects of tPA on the neurovascular unit and also via disruption of the blood brain barrier (BBB). We hypothesized that another mechanism underlying neuroprotective effects of G-CSF is via preservation of the integrity of the BBB through vasculogenic and angiogenic effects of recruited EPCs. The long-term goal of this study is to demonstrate that G-CSF in tandem with tPA will reduce delayed tPA-associated complications and also extend the thrombolytic efficacy of tPA. The overall impact is that at the completion of this study, the findings from this work will lay the foundation for the clinical evaluation of G-CSF in attenuating HT associated with delayed treatment of tPA.