周邊動脈疾病所引起的血管阻塞會造成下肢缺血，並使得缺血區域的組織無法獲得足夠的氧氣與養分供應而逐漸壞死，最終導致肢體喪失。當組織缺血發生時，該區域內的細胞會面臨缺氧的微環境，而缺血所導致的發炎反應及其伴隨而來的免疫細胞會使得局部區域內累積大量的活性氧化物質，傷害細胞中的核酸、蛋白質與脂質，使細胞不易存活。硫化氫為一氣體訊號分子，可做為抗氧化劑，並具有降低氧化壓力、減少細胞凋亡與促進血管新生等生理功能，因此針對缺血部位提供外源性硫化氫，成為一極具潛能的缺血性疾病治療方式。然而硫化氫在體內的存在時間極短，很快就會被代謝成為其他產物，故投遞可以產生硫化氫的前驅物是較為可行的方式。但多數硫化氫前驅物仍有反應速率過快的問題，投遞至體內後可能短時間內就反應完畢，因此無法持續供給組織硫化氫；此外，過高的反應速率可能導致短時間內組織中的硫化氫濃度大幅提升，造成負面影響，反而不利於細胞的生存與生長。在本論文中，我們使用聚乳酸-甘醇酸(poly latic-co-glycotic acid, PLGA)做為藥物載體，用以攜帶疏水性的硫化氫前驅物二烯丙基三硫(diallyl trisulfide, DATS)，期望藉由控制其在體內的釋放情形，以提升治療效果。實驗結果顯示我們成功製備出包覆有DATS之PLGA微米粒子，並能釋放DATS長達一週以上。在體外實驗中，我們發現DATS確實能夠提升細胞在缺氧環境與氧化壓力下的存活率，並藉由調控抗氧化基因之表現以降低氧化壓力，且具有促進血管新生的潛能。而在動物實驗裡，我們以外科手術方式將小鼠左腿股動脈結紮，建立下肢缺血的模式後，再將包覆有DATS之PLGA微米粒子注射至缺血組織周圍，並以單光子放射電腦斷層掃描與組織病理切片染色等方式評估其治療效果。我們發現注射包覆有DATS之PLGA微米粒子可以有效降低缺血組織的氧化壓力、減少細胞凋亡的情形，並能夠誘導組織血管新生，改善患部血液灌流情況，減緩小鼠下肢萎縮。由以上實驗結果可知，本論文所開發出的包覆有DATS之PLGA微米粒子可以有效提升缺血細胞的存活率並促進組織的血管新生，具有應用於缺血性疾病治療的潛能。

In critical limb ischemia, the occlusion of blood vessels results in tissue hypoxia, followed by intense inflammatory response and increased oxidative stress, which ultimately limits the survival of the suffered cells. Hydrogen sulfide (H2S) has become recognized as an important signaling molecule, contributing to many physiological and pathological processes. The protective role in combating cellular apoptosis, oxidative stress, as well as promoting angiogenesis prompted vast interest in the possibility of developing new therapies by delivery exogenous H2S for the treatment of ischemic diseases. In this study, a drug delivery system employed poly(lactic-co-glycolic acid) (PLGA) was employed to load diallyl trisulfide (DATS), an organosulfide that can generate H2S upon reacting with glutathione, to administer exogenous H2S for treating ischemic diseases. By providing exogenous H2S, a receptive cell environment in the target tissue can be realized, and thus the survival rate of the suffered cells as well as the therapeutic effects can be improved considerably. The DATS-loaded PLGA microparticles (MPs) was fabricated by single emulsion. Our in vitro results demonstrate that the DATS-loaded PLGA MPs can enhance cell viability of C2C12 mouse myoblasts under hypoxia/oxidative stresses. In the in vivo experiments, intramuscular injection of the DATS-loaded MPs was performed for the treatment of ischemic mouse hindlimb. The animals that received saline, free DATS or empty MPs serve as controls. We found that therapeutic angiogenesis was enhanced and blood flow recovery and limb salvage were ultimately achieved. The strategy that uses DATS-loaded PLGA MPs may provide a new means of delivering the exogenous H2S for the treatment of ischemic diseases.

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