X-ray & MR-visible Microencapsulation of Allogeneic Arteriogenic Cell Therapeutic

描述(申请人提供)：外周动脉疾病(PAD)影响大约800万至1200万美国人。由于疾病的范围和分布模式，许多患者不适合进行传统的治疗，例如外科搭桥或血管成形术。闭合性垫不仅可能导致休息时或行走时的疼痛(跛行)，如果足够严重，还可能导致肢体远端溃疡，最终需要截肢。此外，严重肢体缺血患者的生活质量评分与晚期癌症患者相当。由于新血管形成的线索放错了地方(因为缺血最严重的区域发生在四肢远端，即足部，而狭窄或闭塞的动脉更近端，即髂骨或股骨疾病)，外源性细胞疗法提供了一种将细胞管理到可能最有帮助的区域的方法。这可以通过直接分化成血管或通过释放适当的细胞因子来帮助新生血管来实现。由于患者的天然干细胞通常是功能障碍的，异基因干细胞可能是为PAD患者提供现成的、高质量的细胞治疗的最佳选择。细胞疗法的临床试验将需要以非侵入性方式监测输送、植入和治疗效果的方法。此外，目前的细胞疗法都存在植入率极低的问题，主要原因是给药后24小时内细胞被破坏。因此，保护干细胞不被早期破坏的方法，以及免疫保护患者免受非侵入性监测的同种异体细胞治疗的排斥反应的方法将是非常有益的。在目前的方案中，我们将开发一种新的方法来组合同种异体间充质干细胞(MSCs)的放射不透明、MR可见微囊化(XMRCap)，该方法可以使用X射线透视、计算机断层扫描(CT)和磁共振成像(MRI)无创地输送和跟踪。对于应用程序的R21阶段，我们将重点关注三个具体目标：1)(1)优化的XMRCap配方可保持细胞活性，具有生物兼容性，并表现出足够的敏感性，可用于非侵入性成像传输；展示使用CT连续跟踪XMRCaps的能力；以及3.证明XMRCaps具有免疫保护作用并提高细胞存活率。在达到R21里程碑后，R33应用程序将在给药后7天通过相对于裸MSCs增强动脉生成的能力来确定在给药后7天的增强植入程度和治疗效果，以增强相关的兔后肢缺血模型的动脉生成。由于XMRCaps由临床级别的产品组成，我们预计这些临床前数据将成为FDA将XMRCaps转化为PAD中的治疗性动脉形成临床试验的安全性和活性数据的基础。将一种新的微胶囊技术用于临床级药物，目前应用的目标是封装来自无关捐赠者的干细胞，这些干细胞可以通过X射线成像和磁共振成像(MRI)看到，以便准确地输送和跟踪患者。微胶囊将：1。)防止异体细胞排斥；2.)与未包裹的细胞相比，提高细胞的存活率；以及使干细胞能够帮助动脉狭窄或闭塞且无法用传统手术或药物治疗的患者形成新的血管。

DESCRIPTION (provided by applicant): Peripheral arterial disease (PAD) affects approximately 8-12 million Americans. Many patients are not candidates for conventional treatments, e.g., surgical bypass or angioplasty, due to the extent and distribution pattern of their disease. Occlusive PAD may not only lead to pain at rest or with walking (claudication), but, if severe enough, may lead to distal limb ulceration and, ultimately, the need for amputation. Moreover, patients with critical limb ischemia have quality of life scores that are comparable to terminal cancer patient. Because the cues for new vessel formation are misplaced (due to the most ischemic areas occurring in the distal limb, i.e., foot, whereas the stenotic or occlusive artery is more proximal, i.e., iliac or femoral disease), exogenous cellular therapy offers a means to administer cells to the regions where they might be most helpful. This can be accomplished by either direct differentiation into blood vessels or by the release the appropriate cytokines to assist in neovascularization. Because patients' native stem cells are often dysfunction, allogeneic stem cells may offer the best choice of cellular products to provide off-the-shelf, high quality, cellular therapy for PAD patients. Clinical trials of cellular therapy will require methods to monitor delivery, engraftment, and therapeutic benefit in a non-invasive manner. In addition, current cellular therapies all suffer from extremely low engraftment primarily due to destruction of the cells in the first 24 hours after administration. Therefore, methods to protect stem cells from early destruction and also immunoprotect the patient from rejection of allogeneic cellular therapies that could be monitored non-invasively would be of tremendous benefit. In the current proposal, we will develop a novel method of combined radiopaque, MR-visible microencapsulation (XMRCap) of allogeneic mesenchymal stem cells (MSCs) that can be delivered and tracked non-invasively using x-ray fluoroscopy, computed tomography (CT), and magnetic resonance imaging (MRI). For the R21 phase of the application, we will focus on three specific aims: 1.) the formulation of an optimized XMRCap that maintains cellular viability, is biocompatible, and demonstrates sufficient sensitivity for non-invasive imaging for delivery; 2.) demonstrate the ability to serially track XMRCaps with CT; and 3.) demonstrate that XMRCaps are immunoprotective and enhance cell survival. After achieving the R21 milestones, the R33 application will determine the degree of enhanced engraftment at 7 days post- administration and therapeutic efficacy by the ability to enhance arteriogenesis relative to naked MSCs in a relevant rabbit model of hindlimb ischemia. Because XMRCaps are composed of clinical grade products, we anticipate that these preclinical data will form the basis of safety and activity data for the FDA for translation of XMRCaps to therapeutic arteriogenesis clinical trials in PAD. Using a novel microencapsulation technique with clinical grade pharmaceuticals, the goal of the current application is to encapsulate stem cells from unrelated donors that can be seen by X-ray imaging and magnetic resonance imaging (MRI) for precise delivery and tracking in patients. The microencapsulation will: 1.) prevent the rejection of foreign cells; 2.) enhance the survival of the cells compared to cells that are not encapsulated; and 3.) enable the stem cells to assist in the development of new vessels in patients whose arteries that are narrowed or occluded and who cannot be treated with conventional surgery or medical therapies.