ROLE OF ENDOTHELIUM IN GRAFT INTIMAL HYPERPLASIA

本建议的长期目标是了解 血管移植物内膜增生中的内皮。 内皮 细胞（EC）衬里的假体移植被认为是因为它已经 显示出降低移植物血栓形成性和血小板活化，以及 提高小口径移植物的短期通畅率。 然而，EC有 潜在的不希望的功能，如生产光滑 肌肉细胞（SMC）有丝分裂原，可能会诱导过度增殖， 内皮下组织中的细胞。 事实上，内膜增生是 通常在首先内皮化的移植区域最为严重，在 邻近的区域。 此外，我们的初步研究 已经提出，接种到移植物上的EC产生血小板衍生的 生长因子样蛋白（PDGFc）在非常高的利率。 这种增长 因子刺激培养的SMC增殖，并被认为是 参与动脉粥样硬化病变的发展。 在这方面的实验 一项提案将检验欧共体扩大的假设， 聚四氟乙烯（ePTFE）移植物产生有丝分裂原，包括PDGFc， 这是负责增加SMC增殖， 内皮下内膜增生。 我们进一步建议， EC活化产生SMC有丝分裂原可能受改变 接枝基质的物理和生物化学性质，或通过 体液环境的变化。 为了验证这些假设，我们采用了体外培养的方法， EC种植的ePTFE假体将与移植物的程度相关 在长达6个月的犬研究中进行内皮化。 在 在内皮化的中间阶段，移植物将被移除，并且 将测量PDGFc的产生并与相邻的细胞的PDGFc产生进行比较。 血管和培养的细胞。 由于SMC和巨噬细胞在一定的 条件下也产生PDGFc，负责PDGFc的移植细胞 将通过使用PDGF A链的原位杂交来鉴定生产 和B链cDNA探针。 此外，还将培养EC和SMC 分别并在体外测量PDGFc的产生。 确定 底物对总有丝分裂原和PDGFc产生、生长因子 将在修饰的底物上研究体外和体内分泌素。 此外，由于鱼油已被证明可以减少移植物内膜 增生，以及最近在体外抑制PDGFc产生， 这些油对种子EC产生生长因子的影响 将研究移植物。如果拟议的研究表明， 血管移植物上细胞的产量仍然很高，即使在 实现稳定的内皮细胞衬里，然后开发 抑制有丝分裂原的产生可能是控制 吻合口内膜增生。

The long-term objective of this proposal is to understand the role of the endothelium in intimal hyperplasia of vascular grafts. An endothelial cell (EC) lining on a prosthetic graft is considered since it has been shown to reduce graft thrombogenicity and platelet activation, as well as improve the short-term patency of small caliber grafts. HOwever, EC have potentially undesirable functions, such as the production of smooth muscle cell (SMC) mitogens which may induce excessive proliferation of cells in the subendothelial tissue. In fact, intimal hyperplasia is often most severe in graft regions that are firs endothelialized, in the areas adjacent to the anastomoses. Furthermore, our preliminary studies have suggested that EC seeded onto grafts produce a platelet-derived growth factor-like protein (PDGFc) at very high rates. This growth factor stimulates the proliferation of cultured SMC and is thought to be involved in atherosclerotic lesion development. Experiments in this proposal will test the hypothesis that EC o expanded polytetrafluoroethylene (ePTFE) grafts produce mitogens, including PDGFc, which are responsible for increased SMC proliferation causing subendothelial intimal hyperplasia. We further propose that this activation of EC to produce SMC mitogens may be regulated by alteration of the physical and biochemical properties of the graft substrate, or by changes in the humoral environment. To test these hypotheses, the production of EC-derived growth factors on EC seeded ePTFE prostheses will be related to the degree of graft endothelialization in canine studies extending up to 6 months. At intermediate stages of endothelialization, the graft will be removed, and PDGFc production will be measured and compared to that of adjacent vessels and to cultured cells. Since SMC and macrophages under certain conditions also produce PDGFc, the graft cells responsible for PDGFc production will be identified by in situ hybridization using PDGF A-chain and B-chain cDNA probes. In addition, EC and SMC will be cultured separately and PDGFc production measured in vitro. To determine the effects of substrate on total mitogen and PDGFc production, growth factor secretin in vitro and in vivo will be studied on modified substrates. Furthermore, since fish oils have been shown to reduce graft intimal hyperplasia, and more recently to inhibit PDGFc production in vitro, the effect of these oils on production of growth factors by EC on seeded grafts will be studied. If the proposed studies show that growth factor production by cells on vascular grafts remains high, even after achievement of a stable endothelial lining, then development of means of inhibiting mitogen production may be necessary to control development of anastomotic intimal hyperplasia.