Strategies for prenatal stem cell transplantation

描述(申请人提供)：宫内造血细胞移植(IUHCT)是一种很有前途的治疗方法，可能适用于大量的遗传性疾病。利用IUHCT小鼠模型，我们建立了跨越全部MHC屏障的混合造血嵌合体，并对植入要求和相关的供者特异性耐受获得了理解。我们已经确定了IUHCT后耐受的机制，并利用产前耐受来促进出生后骨髓移植和免疫治疗，将供者的部分嵌合转换为完全嵌合，跨越全部MHC屏障，而没有毒性。我们的长期目标是将这些成功的策略转化为临床应用，并开发新的、安全的新方法，以实现仅由IUHCT进行治疗性植入。在这个方案中，我们的具体目标是：1)确定决定IUHCT后同种异体移植成败的获得性免疫反应的成分和机制。我们观察到同种异体IUHCT在BM和HSC的植入频率上有明显的差异。这些差异已经被我们目前的大剂量血管内注射细胞技术所掩盖。为了达到这个目的，我们将探讨这样一种假设，即许多供体反应细胞逃脱克隆删除，嵌合体的维持依赖于在供体细胞排斥之前产生足够的外周调节反应。2)通过有针对性的产前免疫治疗来促进植入。我们将研究使用主要表达在造血细胞上的次要组织相容免疫优势抗原作为特定免疫治疗的靶点，以增强无移植物抗宿主病胎儿的植入。3)探讨提高供体细胞归巢和植入的选择性策略。我们还发现了一种通过阻断二肽基肽酶CD26来改善子宫内移植后供体细胞归巢和植入的机制。这项建议中的研究旨在开发和优化IUHCT的新方法，这些方法将安全地移植到大型动物和人类系统。这些研究的最终目标是开发安全有效的策略，可用于广泛的人类遗传性血液病的宫内治疗，包括镰刀细胞病和地中海贫血。

DESCRIPTION (provided by applicant): In utero hematopoietic cell transplantation (IUHCT) is a promising therapeutic approach potentially applicable to a large number of genetic diseases. Utilizing the murine model of IUHCT, we have established mixed hematopoietic chimerism across full MHC barriers and gained understanding into the requirements for engraftment and associated donor specific tolerance. We have determined the mechanism of tolerance after IUHCT, and utilized prenatal tolerance to facilitate postnatal bone marrow transplantation and immunotherapy with conversion of partial to complete donor chimerism across full MHC barriers without toxicity. Our long-term objective is the translation of these successful strategies to clinical application, and the development of novel and safe new approaches to achieve therapeutic engraftment by IUHCT alone. In this proposal our specific aims are: 1) To define the components and mechanism of the adaptive immune response that determine the success or failure of allogeneic engraftment after IUHCT. We have observed that there are clear differences in the frequency of engraftment between congenic and allogeneic IUHCT using BM and HSC. These differences have been unmasked by our current technique of intravascular injection of large doses of cells. In this aim we will investigate the hypothesis that many donor reactive cells escape clonal deletion, and that the maintenance of chimerism is dependent upon generation of an adequate peripheral regulatory response prior to rejection of donor cells. 2) To enhance engraftment by specifically targeted prenatal immunotherapy. We will investigate the use of minor histocompatibility immunodominant antigens expressed predominantly on hematopoietic cells as a target for specific immunotherapy to enhance engraftment in the fetus without GVHD. 3) To investigate selective strategies to improve homing and engraftment of donor cells. We have also identified a mechanism to improve homing and engraftment of donor cells after in utero transplantation by blockade of the dipeptidylpeptidase CD26. The studies in this proposal are designed to develop and optimize novel approaches to IUHCT that will be safely translatable to large animal and human systems. The ultimate goal of these studies is to develop safe and effective strategies that can be translated to the in utero treatment of a broad range of human genetic hematologic disorders including Sickle Cell Disease and Thalassemia.