Enhancing immune reconstitution after implantation of postnatal allogeneic thymus

描述（由申请人提供）：由于胸腺发育缺陷导致的严重先天性T淋巴细胞减少症发生在迪乔治异常。手术植入出生后，异体，培养胸腺碎片已被执行，试图提供一个适当的微环境，为这些患者的胸腺发育。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，自身免疫性疾病是一个常见的问题。在临床环境中，对胸腺重建的细胞机制进行详细分析是不可能的。我们的目标是在免疫缺陷小鼠模型中使用人类骨髓-胸腺嵌合体来创建一个平台，从细胞水平上描述胸腺细胞是如何在人类胸腺植入物中产生的，以及如何改善胸腺生成。为了实现这一目标，我们将汇集来自正常人类胸腺发育和胸腺血管生态位研究的信息。使用免疫缺陷小鼠模型，我们注意到新生儿胸腺为造血干细胞移植后快速胸腺播种和胸腺生成提供了独特的接受环境。我们的数据表明，新生儿和成人胸腺血管存在质的差异，这些差异是由高水平的血管内皮生长因子（VEGF）介导的。我们假设，新生胸腺的血管内皮生长因子反应介导快速和强大的胸腺发育。此外，我们提出在植入胸腺组织中表达VEGF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：目的：探讨出生后培养胸腺植入后建立人胸腺功能重建的细胞机制。2. 目的：确定人出生后胸腺植入物中VEGF的表达是否会改善植入物的存活和胸腺发育。除了这些研究与diggeorge异常的治疗直接相关外，这些研究将提供一种技术上可行的方法来实验地操纵人类胸腺微环境，并在内源性人类造血的背景下检查这种操作的生物学。了解血管生态位在胸腺重构中的作用，可以为胸腺细胞区室内的串扰机制提供新的见解。

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.