Bioengineering A Bioartificial Pancreas

描述（由申请人提供）：尽管埃德蒙顿方案承诺，但需要使用免疫抑制药物和人类胰岛的严重短缺仍然是临床胰岛移植的主要障碍。克服这两个障碍的一个有吸引力的策略是在移植前对胰岛进行微胶囊化技术。尽管如此，在这种方法成为临床现实之前，仍有许多问题需要解决。微囊化胰岛移植目前是在未修饰的腹膜腔中进行的，因为需要大的空间来容纳大的移植物体积，而传统的胰岛移植部位，如肝脏，不适合。微胶囊相对较大的表面体积比和腹膜腔内缺乏血液供应，给被包裹的胰岛提供足够的氧气和营养以及被包裹的胰岛与体循环之间的葡萄糖和胰岛素交换带来了挑战。我们将验证一个假设，即由于有足够的氧气和营养供应，囊化胰岛移植的新生血管会提高胰岛的活力。本课题的具体目标是：1)设计一种血管生成蛋白的最佳递送系统，以诱导海藻酸盐微胶囊周围的新血管形成。将新型HBGAM-R136K血管原包埋在藻酸盐-多鸟氨酸-藻酸盐微胶囊的藻酸盐层中，我们将首先利用荧光和图像处理技术研究其体外释放动力学以及体外微血管的性质和水平。然后，我们将在体内研究中检查组织血管生成和纤维化对蛋白质的反应。2)研究血管生成蛋白包封移植胰岛诱导新生血管的功能。利用正常Lewis大鼠胰岛供体和链ptozotocin糖尿病Lewis大鼠受体的等移植模型，我们将用血管生成蛋白包埋胰岛，并评估移植后90天内受体大网膜囊内的血糖和胰岛素水平。3)确定优化后的生物人工胰腺模型在大鼠同种异体移植中的效果。我们将从正常Wistar-Furth大鼠中分离并包封胰岛，并将其移植到糖尿病Lewis大鼠中。4)评估生物人工胰腺在异种移植动物模型中的功能——首先，将人胰岛移植到糖尿病Lewis大鼠体内90天；第二，在患有糖尿病的猴子身上移植人类胰岛180天。公共卫生相关性：现在很清楚胰岛移植为1型糖尿病患者提供了最好的治疗选择。然而，人类胰岛的短缺和需要使用危险药物来防止移植排斥反应仍然是糖尿病患者常规使用胰岛移植的主要障碍。该项目的目的是开发一种可行的策略来克服这两个障碍，使胰岛移植成为糖尿病患者更有吸引力和广泛使用的治疗选择。

DESCRIPTION (provided by applicant): Despite the promise of the Edmonton protocol, the need to use immunosuppressive drugs and the severe shortage of human islets remain major barriers to clinical islet transplantation. An attractive strategy to overcome these two barriers is the technique of microencapsulation of islets prior to transplantation. Still, there are a number of issues that need to be resolved before this approach can become a clinical reality. Microencapsulated islet transplantation is currently performed in the unmodified peritoneal cavity because of the need for a large space to accommodate the large graft volume for which conventional islet transplant sites, such as the liver, are not suitable. The relatively large surface-to-volume ratio of microcapsules and the absence of a blood supply in the peritoneal cavity pose challenges to adequate supply of oxygen and nutrients to the encapsulated islets as well as exchange of glucose and insulin between the encapsulated islets and the systemic circulation. We will test the hypothesis that neovascularization of encapsulated islet transplants would enhance the viability of the islets because of adequate supply of oxygen and nutrients. The specific aims of this proposal are: 1) To design an optimum delivery system for angiogenic proteins to induce neovascularization around alginate microcapsules. After encapsulating the novel HBGAM-R136K angiogen in either of the alginate layers of alginate-polyornithine- alginate microcapsules, we will first study its release kinetics in vitro and the nature and level of microvasculature in vitro using fluorescence and image processing techniques. We will then examine tissue angiogenic and fibrotic responses to the protein in in vivo studies. 2) To determine the function of islets encapsulated and transplanted with the angiogenic protein to induce neovascularization. Using an isograft model of normal Lewis rat islet donors and Streptozotocin-diabetic Lewis rat recipients, we will co- encapsulate islets with angiogenic protein, and will assess blood glucose and insulin levels for 90 days after transplantation in omentum pouches of recipients. 3) To determine the efficacy of the optimized model of this bioartificial pancreas in a rat allograft. We will isolate and encapsulate islets from normal Wistar-Furth rats and transplant them in diabetic Lewis rats. 4) To assess the bioartificial pancreas function in xenograft animal models - first, human islets transplanted in diabetic Lewis rats for 90 days; and second, human islet transplants in diabetic monkeys for 180 days. PUBLIC HEALTH RELEVANCE: It is now clear that islet transplantation provides the best treatment option for individuals afflicted with Type 1 diabetes. However, the shortage of human islets and the need to use risky drugs to prevent transplant rejection remain major obstacles to routine use of islet transplantation in diabetic patients. The purpose of this project is to develop a viable strategy to overcome these two barriers and make islet transplantation a more appealing and widely used treatment option for diabetic patients.