摘要:神經細胞有神經元(Neuron)和神經膠細胞(Glia)兩大類細胞。神經元細胞屬神經系統構造 和功能的基本單位,乃負責神經訊息的傳遞。而神經膠細胞種類繁多,數量遠大於神經元細 胞,本身不具神經訊息傳遞功能,負責維持神經元構造、供應所需養分、調節環境恆定、保 護或清除異物、協助神經元的生長發育、加速神經衝動的傳遞速率等功能。中風及腦血管相 關疾病造成的死亡人數高居世界十大死因中的第二位(在台灣為第三位),也是造成長期失能 最重要的疾病。因中風及腦血管相關疾病所造成的死亡、併發症、以及照護的需求,會造成 龐大的社會成本。據統計,初次腦中風後之5年内累積復發率為26.4%,10年内累積復發率 為39.2%。目前對缺血性腦中風較有效的積極性臨床治療僅有血栓溶解術(thrombolysis),但 此治療方法受限於較短的治療黃金期(三小時内)、以及腦出血之風險,所以在臨床上並無法 廣泛性使用。因此,預防勝於治療,如何找出有效對於腦中風高危險群例如有高血壓、心臟 病、高血脂、糖尿病等患者的預防或腦中風癒後患者復發(recurrence)防治是目前對缺血性腦 中風防治的當務之急,也是非常重要的研究課題。另一方面,超音波目前在一般臨床醫學上 的應用主要是作為診斷用的即時造影設備,或是作為侵入性治療的即時定位。近年來,超音 波也被發現可以做為治療疾病的一種方法,其主要應用有兩個方面,一種是高強度聚焦式超 音波(high-intensity focused ultrasound, HIFU),另一種是低強度脈衝式超音波(low-intensity puled ultrasound, LIPUS)。高強度聚焦式超音波可引發熱效應,在人體組織中具有良好的穿透 性,可以將能量傳至深層組織,可以造成聚焦區域溫度升高,燒灼破壞蛋白質或引起組織内 細胞凋亡及傷害等,此種大能量的累積可以應用在腫瘤細胞的熱燒灼治療上。但是以上的治 療方法只能利用高溫的熱治療來切除病灶發生的區域,可能無法達到完全治癒效果,通常對 周圍的正常細胞也會有所影響。LIPUS相較於HIFU,所造成傷害的可能性較低也可以恢復, 所以應用的範圍也可更為廣泛。運用LIPUS作為缺血性腦中風預防或復發防治是有其潛在意 義與應用價值,但目前很缺乏相關之研究,這也是我們感興趣而要積極探討的課題。本研究 計晝之確切目標:本研究旨在利用細胞及實驗動物模式來探討低強度脈衝式超音波是否對於 缺血性腦中風模式有預防或復發防治的效果及可能之作用機轉。如果實驗證實有治療效果, 則可以考慮應用於臨床,以尋求對缺血性腦中風之預防或復發防治有更進一步的發展。本研 究計晝為兩年期計晝,長期目標和研究重點為:1.利用神經細胞(包括神經元及神經膠細胞) 培養模式探討LIPUS對於缺氧/再灌流(hypoxia/reperfusion)誘導之腦細胞傷害之預防與可能作 用機轉。2.利用小鼠大腦動脈阻塞(middle cerebral artery occlusion, MCAO)引發缺血狀態而後 再引導血液再灌流之動物模式來模擬缺血性腦中風,進而探究LIPUS是否對於缺血性腦中風 有預防效果及可能之作用機轉。3.利用神經細胞(包括神經元及神經膠細胞)培養模式探討 LIPUS對於二次缺氧/再灌流傷害(模擬復發(再中風)情況)防治作用與可能作用機轉。4.利用 小鼠MCAO缺血/再灌流動物模式進行二次缺血性腦中風(stroke recurrence)模式來模擬中風 後再復發情形,進而探究LIPUS是否對於缺血性腦中風復發有防治效果及可能之作用機轉。 本計晝為一新的概念,利用非侵入性之診斷用途相當強度之LIPUS嘗試用於缺血性腦中風之 預防及再中風之防治的研究,若細胞及動物模式實驗可以證明此方法對於預防缺血性腦中風 或其復發的可能性,則未來進行臨床試驗或甚至應用於臨床上將是可預期或期待的。
Abstract: Nerve tissue is composed of neurons and glial cells. Neuron is the basic unit of structure and function in the nervous system and is responsible for nervous signaling transduction. Glial cells are belonging to the supporting cells, which numbers are much larger than neurons. The functions of glial cells contain: maintaining neuronal structure, supply the necessary nutrients, regulate the environment constant, protect or remove foreign bodies, assist the growth and development of neurons, and accelerate the conduction rate of nerve impulses and so on. According to World Health Organization, stroke and cardiovascular disease are the second leading causes of death worldwide. Stroke occurs because of interruption of blood flow due to thrombosis. Patients with stroke will experience sudden paralysis, loss of vision or death. Hypoxia/reperfusion (H/R) injury occurs when thrombosis is removed. H/R injury can cause damage to brain cells through ATP depletion, reactive oxygen species, inflammation or apoptosis. Moreover, the pooled cumulative risk of stroke recurrence has been reported to be 26.4% at 5 years and 39.2% at 10 years after initial stroke. Currently effective treatment for ischemic stroke is only thrombolysis, but this approach is limited by the treatment timing and the risk of cerebral hemorrhage. Therefore, prevention is better than treatment. How to find an effective method to prevent (1) the development of stroke in the patients with high-risk for stroke such as hypertension, heart disease, hypercholesterolemia, and diabetes or (2) the development of stroke recurrence is urgent. On the other hand, ultrasound is widely used for diagnostic medical imaging, and is a safe and effective modality to visualize pathological lesions in human body. In recent years, ultrasound has also been found to be used as a method for treating a disease, its main application has two aspects, one is a high intensity focused ultrasound formula (HIFU), and the other is a low-intensity pulsed ultrasound (LIPUS). HIFU can lead to thermal effects style, with good penetration in human tissues, energy can be transferred to the deep tissue, the focus area can cause the temperature rises, burning causing damage to proteins or cell injury/apoptosis within tissues. Accumulation of such large energy can be applied to the thermal cautery treatment of tumor cells. But the above method using high-temperature heat treatment usually might damage the surrounding normal cells or tissues. LIPUS, as compared to HIFU, is less likely to cause harm and can be restored, so the range of applications can be more extensive. However, the preventive effects of LIPUS on ischemic stroke and stroke recurrence are still unclear. The aims of this research project are to investigate the preventive effects of LIPUS on ischemic stroke and stroke recurrence using cell and animal models. This is a two-year project. The goals and key points of this project are: 1. cellular models of ischemia/reperfusion in neuronal cells and glial cells: To investigate the preventive effects and possible mechanisms of LIPUS on hypoxia/reperfusion-induced neuronal and glial cell injuries; 2. a cerebral ischemia/reperfusion mouse model: To investigate the effects and possible mechanisms of LIPUS on middle cerebral artery occlusion-induced brain injuries; 3. cellular models of recurrent ischemia/reperfusion in neuronal cells and glial cells: To investigate the preventive effects and possible mechanisms of LIPUS on recurrent hypoxia/reperfusion-induced neuronal and glial cell injuries; 4. a recurrent cerebral ischemia/reperfusion mouse model: To investigate the effects and possible mechanisms of LIPUS on recurrent stroke-induced brain injuries. This project is a new concept. The non-invasive LIPUS, which intensity is in the range of diagnostic ultrasound, will be used to test its effects on ischemic stroke. If these cell and animal model experiments can prove that this method is work for the prevention of ischemic stroke and stroke recurrence, the clinical trials or even used in clinical application will be expected or anticipated in the future.