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標題: Physical stimulation and repair in small diameter vascular grafts
作者: 黃琮濱
Huang, Tsung Bin
關鍵字: 超音波;ultrasound;低功率雷射;內皮細胞;人工小血管;骨髓間葉幹細胞;lower power laser;endothelial cell;vascular graft;mescenchymal stem cell
出版社: 化學工程學系
EC dysfunction is a main cause of the severity of cardiovascular disease, a substitute for blood vessel is needed to replace the damaged vessel. However, the low long-term patency of small-diameter vascular grafts has been a challenge to researchers in this area. This limitation is due in large part to lack of endothelization and to the frequency of intima hyperplasia near anastomosis. The purpose of this project is to employ physical stimulation to increase the endothelization and thus to improve the long-term patency of the small-diameter vascular grafts.
Specifically, physical stimulations such as ultrasound and low-power laser will be employed to enhance the tissue repair. First, we want to evaluate the effect of therapeutic ultrasound on endothelial cells. Second, RGD-containing protein (CBD-RGD), as well as ultrasonic stimulation to enhance the seeding of endothelial cells on the luminal surface of polyurethane small-diameter vascular grafts was evaluated. Third, evaluate the effect of ultrasound on the nitride oxide synthase expression in endothelial cells. Fourth, we will go further into the effect of ultrasound combined low-power laser on endothelial cells. Finally, we evaluated the effects of ultrasound on the differentiation of the mesenchymal stem cells.
Based on our results, low-intensity ultrasound could change the morphology, enhanced the NO and Ca2+ release and matrix secretion of endothelial cells and such effects persisted when pre-exposed cells were seeded to another substrate. The cells pre-exposed to ultrasound were more spread on the substrate. The actin stress fibers of ultrasound pre-exposed cells on RGD-modified surfaces were especially intense and well oriented. Ultrasound could probably activate cellular integrins and subsequently allowing RGD to bind them. A much firmer adhesion of ultrasound pre-exposed endothelial cells to the biomaterial surface coated with the RGD-containing protein was demonstrated. Furthermore, polyurethane small diameter vascular grafts seeded with ultrasound pre-exposed endothelial cells showed enhanced cell retention on graft surfaces upon flushing. The bioeffect of ultrasound is associated with eNOS gene upregulation. Laser stimulation enhanced the NO and Ca2+ release from the endothelial cells and influenced the cell morphology and matrix secretion but did not promote cell growth. Finally, chondrocyte differentiation was enhanced in the presence of transforming growth factorβ1(TGF-β1) by ultrasound pre-exposure mesenchymal stem cells. In future, we hope to investigate the differentiation of mesenchymal stem cells into cells with phenotypic and function features of endothelial cells by ultrasound pre-exposure.

研究發現超音波與低功率雷射對組織修復有不錯的效果,本研究利用物理刺激產生組織修復功能,來探討超音波和低功率雷射對細胞的作用關係。整個研究主體分成五部分; 一是探討超音波對內皮細胞的作用。二是結合超音波與RGD基因工程蛋白質與明膠共同改質的表面,評估經超音波刺激細胞與RGD作用,以及改善人工小血管內皮細胞植覆之評估。三是評估超音波對一氧化氮合成酶基因調控。四是將結合超音波和低能量雷射作用,評估兩者對細胞的作用機制。最後是評估超音波對提升骨髓間葉幹細胞分化的影響。
超音波對內皮細胞之生物效應,結果發現對內皮細胞生長速率影響成效不大,但形態改變,NO釋放量、細胞外鈣離子濃度、細胞外基質分泌增加,細胞骨架蛋白改變,這些結果會在超音波刺激後會持續存在。也就是經超音波刺激細胞後再與RGD蛋白質結合,更能增加細胞在PU人工血管貼附能力。而超音波對內皮細胞一氧化氮合成酶(eNOS)影響,結果發現,經超音波刺激,會使eNOS基因表現增加。此外,低功率雷射對內皮細胞影響和超音波相同,會使內皮細胞NO釋放量、細胞外鈣離子濃度、細胞外基質分泌增加,對細胞生長會有抑制影響。而超音波與雷射結合仍具有一樣的效果,但在細胞型態上變化較為明顯。最後發現骨髓間葉幹細胞經超音波刺激後再加入TGF-β1 分化劑,結果會使骨髓間葉幹細胞加速分化成軟骨細胞。未來研究希望利用超音波效應使幹細胞加速分化成內皮細胞。
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