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

描述（由申请人提供）：外周动脉疾病（PAD）影响了大约800 - 1200万美国人。由于疾病的范围和分布模式，许多患者不适合常规治疗，例如手术搭桥或血管成形术。PAD闭塞不仅会导致休息或行走时疼痛（跛行），而且，如果严重到一定程度，可能会导致远端肢体溃疡，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是错位的（由于大多数缺血区域发生在远端肢体，如足，而狭窄或闭塞的动脉更近端，如髂或股疾病），外源性细胞治疗提供了一种将细胞输送到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。由于患者的原生干细胞经常出现功能障碍，异体干细胞可能为PAD患者提供现成的、高质量的细胞治疗提供最佳的细胞产品选择。细胞治疗的临床试验需要以非侵入性的方式监测移植物的输送、植入和治疗效果。此外，目前的细胞疗法都有极低的植入性，主要是由于在给药后的最初24小时内细胞被破坏。因此，保护干细胞免受早期破坏的方法和免疫保护患者免受异体细胞治疗的排斥反应，这些方法可以无创地监测，将是巨大的益处。在目前的提案中，我们将开发一种结合放射不透明，mr可见的异体间充质干细胞（MSCs）微胶囊化（XMRCap）的新方法，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）进行无创递送和跟踪。对于R21阶段的应用，我们将专注于三个具体目标：1.优化XMRCap的配方，保持细胞活力，具有生物相容性，并表现出足够的灵敏度，用于非侵入性成像；2)演示用CT连续跟踪xmrcap的能力；3.)证明xmrcap具有免疫保护作用并能提高细胞存活率。在达到R21里程碑后，R33的应用将在给药后7天确定增强的植入程度和治疗效果，通过增强相对于裸MSCs在相关兔后肢缺血模型中的动脉生成能力。由于XMRCaps是由临床级产品组成，我们预计这些临床前数据将成为FDA将XMRCaps转化为PAD治疗性动脉发生临床试验的安全性和活性数据的基础。使用一种新型的临床级药物微胶囊技术，当前应用的目标是封装来自非亲属供体的干细胞，这些干细胞可以通过x射线成像和磁共振成像（MRI）看到，以便在患者中精确输送和跟踪。微囊化将：1.)防止外来细胞的排斥反应；2)与未包被的细胞相比，提高细胞的存活率；3)使干细胞能够帮助那些动脉狭窄或闭塞，无法通过常规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.