Enhancing immune reconstitution after implantation of postnatal allogeneic thymus

描述（由申请方提供）：由于胸腺发育缺陷，DiGeorge异常发生重度先天性T淋巴细胞减少症。为了给这些患者的胸腺生成提供合适的微环境，已经进行了出生后同种异体培养胸腺片段的手术植入。尽管这种方法取得了一些成功，但外周T细胞数量一直很低，自身免疫性疾病是常见的问题。在临床环境中不可能对植入物内发生的胸腺重建的细胞机制进行详细分析。我们的目标是在免疫缺陷小鼠模型中使用人骨髓-胸腺嵌合体来创建一个平台，从该平台我们可以在细胞水平上描绘胸腺细胞如何在人胸腺植入物中产生，以及如何改善胸腺生成。为了实现这一目标，我们将汇集我们的研究信息正常人胸腺，胸腺血管生态位。使用免疫缺陷小鼠模型，我们已经注意到，新生儿胸腺提供了一个独特的接受环境，快速胸腺播种和造血干细胞移植后的胸腺生成。我们的数据表明，新生儿和成人胸腺血管之间存在质的差异，这些差异是由高水平的血管内皮生长因子（VEGF）介导的。我们推测新生儿胸腺的VEGF反应性血管系统介导快速和稳健的胸腺生成。此外，我们认为VEGF在移植胸腺组织中的表达将提高宿主造血细胞胸腺重建的速度和质量。我们提出以下具体目标：1。目的：探讨人胸腺移植后造血重建的细胞学机制。2.确定人出生后胸腺植入物中VEGF表达是否会改善植入物存活和胸腺生成。除了这些研究与DiGeorge异常治疗的直接相关性外，这些研究还将提供一种技术上可行的方法，以体外实验方式操纵人类胸腺微环境，并在内源性人类造血的背景下检查此类操纵的生物学。了解胸腺重建中的血管龛的作用，可能会提供新的见解串扰的胸腺细胞室内的机制。 公共卫生相关性：将分子特异性靶向表达至人胸腺的能力对于原发性免疫缺陷如DiGeorge异常和在整个出生后生活中发展的获得性胸腺功能不全状态具有广泛的治疗潜力。

DESCRIPTION (provided by applicant): Severe congenital T lymphopenia occurs in DiGeorge anomaly as a result of a developmental defect of the thymus gland. Surgical implantation of postnatal, allogeneic, cultured thymic fragments has been performed in an attempt to provide an appropriate microenvironment for thymopoiesis in these patients. Despite some success with this approach, peripheral T cell numbers have remained consistently low and autoimmune disease is a frequent problem. Detailed analysis of the cellular mechanisms of thymic reconstitution that occur within the implants is not possible in the clinical setting. Our goal in this proposal is to use a human marrow- thymus chimera in an immune deficient mouse model to create a platform from which we can delineate on a cellular level how thymocytes are generated in the human thymic implants, and how thymopoiesis might be improved. To achieve this goal, we will bring together information from our studies of normal human thymopoiesis, and of the thymic vascular niche. Using immune deficient murine models, we have noted that the neonatal thymus provides a uniquely receptive environment for rapid thymic seeding and thymopoiesis after hematopoietic stem cell transplantation. Our data shows that qualitative differences exist between the neonate and adult thymic vasculature, and that these differences are mediated by high levels of Vascular Endothelial Growth Factor (VEGF). We hypothesize that the VEGF responsive vasculature of the neonatal thymus mediates rapid and robust thymopoiesis. Furthermore, we propose that expression of VEGF in implanted thymic tissue will improve the speed and quality of thymic reconstitution from host hematopoietic cells. We propose the following Specific Aims: 1. To determine the cellular mechanisms by which reconstitution of human thymopoiesis is established after implantation of postnatal cultured thymus. 2. To determine if VEGF expression in human postnatal thymic implants will improve implant survival and thymopoiesis. In addition to the direct relevance of these studies to the treatment of DiGeorge anomaly, these studies will provide a technically feasible approach to manipulate the human thymic microenvironment experimentally ex vivo, and examine the biology of such manipulations in the context of endogenous human hematopoiesis. Understanding the role of the vascular niche in thymic reconstitution may provide novel insight into mechanisms of cross-talk within the cellular compartments of the thymus. PUBLIC HEALTH RELEVANCE: The ability to target expression of molecules specifically to the human thymus has broad therapeutic potential for both primary immune deficiencies like DiGeorge anomaly and for acquired states of thymic insufficiency that develop throughout postnatal life.