Normalization of Sickle Cell Disease bone marrow niche defects by RBC transfusion

项目摘要 迄今为止，镰状细胞病（SCD）的唯一治疗选择是同种异体HSC移植。最近， 已经开始了利用基因校正的自体HSC的临床试验，并且有很大的希望。然而 在SCD患者中进行HSC移植仍然存在显著的局限性和挑战。人源化SCD小鼠 我们首次发现SCD对骨髓（BM）血管和血管周围的病理影响， 被认为对HSC移植和稳态造血至关重要的小生境。具体而言是 研究揭示了一种紊乱的和结构异常的BM新生血管网络， 高度迂曲的小动脉占据大部分BM腔，以及破碎的窦状血管 充满了红细胞和髓细胞的聚集体。此外，产生CXCL 12的数量 血管周围间充质小生境细胞减少，从而进一步支持了造血小生境的缺陷。 SCD小鼠。进一步的研究提供了SCD BM模型，其中RBC流动缓慢和血管闭塞 进一步减少生理缺氧BM腔中的局部氧可用性。这些事件引发了 有利于异常血管生长的血管生成环境。值得注意的是，扭曲的新生血管网络 通过6周的输血完全逆转，突出了血管生态位的可塑性。 此外，未发表的初步数据表明，长期（16周）HSC重建， 移植到SCD小鼠中的细胞明显受损。总的来说，这些研究让我们假设 HSPCs植入SCD BM的受损是由细胞的结构和功能异常引起的。 造血血管和/或间充质小生境;且关键血管小生境细胞缺陷校正将 改善HSPC植入。干细胞动员也可能受到骨髓小生境的影响，我们将寻求 了解干细胞如何从骨髓进入SCD的血液。因此，提出了三个目标来测试 这些假设：1.在分子和细胞水平上确定人源化SCD中的SCD生态位缺陷 小鼠2.确定哪些小生境缺陷通过输血得以正常化，并定义BM小生境 患者的缺陷; 3.以确定BM生态位缺陷和受损的HSCP植入之间的联系。 总的来说，这些研究将有助于优化有效和长期造血的方法。 在治愈性疗法的背景下植入。

Project Summary To date, the only curative option for Sickle Cell Disease (SCD) is transplantation of allogeneic HSC. Recently, clinical trials utilizing gene corrected autologous HSC have been initiated and hold much promise. However significant limitations and challenges remain for HSC transplantation in SCD patients. In humanized SCD mice we showed for the first time the pathologic impact of SCD on bone marrow (BM) vascular and perivascular niches that are deemed critical to HSC transplantation and steady state hematopoiesis. Specifically, the studies uncovered a disorganized and structurally abnormal BM neovascular network of increased numbers of highly tortuous arterioles occupying the majority of the BM cavity, as well as fragmented sinusoidal vessels filled with aggregates of erythroid and myeloid cells. Additionally, the number of CXCL12 producing perivascular mesenchymal niche cells, was reduced thus further supporting a defective hematopoietic niche in SCD mice. Further investigations provided a model of SCD BM, where slow RBC flow and vaso-occlusion further diminish local oxygen availability in the physiologically hypoxic BM cavity. These events trigger an angiogenic milieu conducive to aberrant vessel growth. Remarkably, the distorted neovascular network was completely reversed by a 6 weeks of blood transfusion highlighting the plasticity of the vascular niche. Additional, unpublished preliminary data indicate that long-term (16 weeks) HSC reconstitution when transplanted into SCD mice is significantly compromised. Collectively, these studies have led us to hypothesize that impaired engraftment of HSPCs into SCD BM is caused by structural and functional abnormalities of the hematopoietic vascular and/or mesenchymal niche; and that correction of key vascular niche cell defects will improve HSPC engraftment. Stem cell mobilization may also be affected by the BM niche and we will seek to understand how stem cells egress from the BM to the blood in SCD. Thus three aims are proposed to test these hypotheses: 1. to define the SCD niche defects at the molecular and cellular level in humanized SCD mouse 2. to determine which niche defects are normalized by blood transfusion and define the BM niche defects in patients; and 3. to ascertain the link between BM niche defects and impaired HSCP engraftment. Collectively, these investigations will help optimize approaches towards efficient and long-term hematopoietic engraftment in the context of curative therapies.