Elastin-derived Scaffolds for Tissue Engineered Small Diameter Vascular Grafts

描述(申请人提供)：外周或冠状动脉搭桥术每年需要100多万个小直径血管移植物。选择的管道是自体静脉或动脉，但由于先前存在的疾病或以前的收获，这些管道并不总是可用的。商业上可用的生物材料，如膨体聚四氟乙烯(EPTFE)，在最初的5年内可以很好地发挥大直径血管移植的作用，但此后由于愈合不全和缺乏保护性内皮层而显着失败。临床使用直径小于6 mm的ePTFE移植物与近端吻合口的高度狭窄相关，并最终由于血栓形成和内膜增生而闭塞。因此，需要能够支持管腔内皮层的新的生物材料来开发功能性的小直径血管移植物。这项研究与公共卫生高度相关，因为在美国和南非等第三世界国家，血管疾病是卫生保健的一个非常重要的章节。长期目标：开发“现成”的小直径移植物，以促进稳定的、抗剪切的内皮细胞层的形成，以保护移植物免受闭塞。种植后血管内皮细胞的自发覆盖可能通过两种独立的机制发生：1)跨吻合口内皮化，即内皮细胞横向迁移，覆盖移植物的管腔表面；2)跨壁内皮化，即内皮细胞通过支架的厚度迁移，建立新的内膜的血管生成过程。由于经吻合口内皮化在人类植入物中似乎是有限的(与动物模型相比)，这两种机制都将在拟议的研究中进行研究。工作假设：植入后促进内皮化的工程弹性蛋白支架可以制造出专利的小直径血管移植物。克莱姆森大学的PI正在开发多孔弹性蛋白衍生血管移植物(EDVGs)，并用五没食子酰葡萄糖(PGG)治疗以实现可逆稳定。在短期植入研究中，EDVGs被发现是非血栓形成的，表现出足够的弹性、破裂压力和顺应性，并且降解缓慢，在皮下研究中促进愈合和支持细胞再生。方法：PI‘s组制备的弹性蛋白管道将在开普敦大学植入大鼠肾下动脉，以评估：(I)生物相容性、通畅性和支持跨吻合口内皮化的能力(Aim 1)，以及(Ii)跨壁内皮化，该模型由开普敦大学开发，通过在植入前将测试段插入ePTFE移植物材料的两节之间(Aim 2)。在啮齿动物模型中进行评估后，EDVGs将被植入猪的颈动脉间置移植物，这是一种更具临床意义的大型动物模型(目标3)。展示这些弹性蛋白衍生支架的通畅性和内皮化具有未来临床应用的巨大潜力。拟议的研究将主要在南非开普敦大学心血管研究股与高级讲师Deon Bezuidenout博士和系主任Peter Zilla教授合作进行，作为NIH补助金R01HL093399(PI，Dan Simion escu博士)和R21EB009835(PI，本提案的共同研究员)在2011年1月1日至2013年12月31日期间的合乎逻辑的延伸。

DESCRIPTION (provided by applicant): More than 1 million small diameter vascular grafts are needed every year for peripheral or coronary bypass surgery. The conduit of choice is an autologous vein or artery, but these are not always available due to pre-existing conditions or previous harvesting. Commercially available biomaterials such as expanded polytetrafluoroethylene (ePTFE) function well as large diameter vascular grafts in the first 5 years but fail dramatically thereafter because of incomplete healing and lack of a protective endothelial layer. Clinical use of ePTFE grafts below 6 mm in diameter is associated with a high rate of narrowing at the proximal anastomosis and ultimately occlusion due to thrombosis and intimal hyperplasia. Thus, new biomaterials capable of supporting a luminal endothelial layer are needed for development of functional small diameter vascular grafts. This study is highly relevant to public health because vascular disease is a very important chapter of health care in the US as well as in third world countries such as South Africa. Long term objective: To develop "off-the-shelf" small diameter grafts that would promote formation of a stable, shear-resistant, endothelial layer to protect the graft from occlusion. Spontaneous luminal coverage with endothelial cells after implantation may occur via two independent mechanisms: 1) Trans-anastomotic endothelialization, whereby endothelial cells migrate laterally across the anastomosis to cover the luminal graft surface and 2) Trans-mural endothelialization, an angiogenic process by which endothelial cells migrate through the thickness of the scaffold to establish a neo-intima. Since trans-anastomotic endothelialization appears to be limited in human implants (as compared to animal models), both mechanisms will be investigated in proposed studies. Working hypothesis: Patent small diameter vascular grafts can be produced by engineering elastin scaffolds that promote endothelialization after implantation. The PI at Clemson University is developing porous elastin-derived vascular grafts (EDVGs) and treatment with penta-galloyl-glucose (PGG) for reversible stabilization. EDVGs were found to be non-thrombogenic in short term implantation studies, exhibited adequate elasticity, burst pressure and compliance, and also degraded slowly, facilitating healing and supporting cell repopulations in subcutaneous studies. Approach: Elastin conduits prepared in the PI's group will be implanted at the University of Cape Town into the rat infrarenal aorta to assess: (i) biocompatibility, patency and ability to support trans- anastomotic endothelialization (Aim 1), and (ii) trans-mural endothelialization in an isolated composite loop model developed by the University of Cape Town whereby the test segment is interposed in between two sections of ePTFE graft material before implantation (Aim 2). After evaluation in the rodent models, EDVGs will be implanted as carotid interposition grafts in pigs, a more clinically relevant large animal model (Aim 3). Demonstration of patency and endothelialization of these elastin-derived scaffolds has great potential for future clinical applications. The proposed research will be performed primarily in the Cardiovascular Research Unit, University of Cape Town, South Africa, in collaboration with Dr. Deon Bezuidenhout, senior lecturer and Professor Peter Zilla, head of department, both acting as co-investigators, as a logical extension of NIH grants R01HL093399 (PI, Dr. Dan Simionescu) and R21EB009835 (PI, Dr. Agneta Simionescu, co-investigator for this proposal), during the period 01/01/2011 to 12/31/2013.