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

项目摘要 到目前为止，治疗镰刀细胞病(SCD)的唯一选择是移植异基因HSC。最近， 利用基因矫正的自体HSC进行的临床试验已经启动，前景看好。然而， 干细胞移植在SCD患者中仍然存在显著的局限性和挑战。在人源化的SCD小鼠中 我们首次展示了SCD对骨髓(BM)血管和血管周围的病理影响 被认为对造血干细胞移植和稳定状态造血至关重要的利基环境。具体地说， 研究发现了一个无序和结构异常的骨髓新生血管网络，其数量增加 占据BM腔大部分的高度扭曲的小动脉，以及碎裂的窦状血管 充满红系和髓系细胞的聚集物。此外，生产CXCL12的数量 血管周围间充质龛细胞减少，从而进一步支持有缺陷的造血龛 SCD小鼠。进一步的研究提供了一种SCD BM的模型，在该模型中，红细胞缓慢流动和血管闭塞 进一步降低生理缺氧性BM腔的局部氧气供应。这些事件会触发 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，突出了血管壁龛的可塑性。 另外，未公布的初步数据表明，长期(16周)的HSC重建 移植到SCD小鼠体内的效果显著受损。总而言之，这些研究引导我们提出了假设 HSPC植入SCD BM的损害是由SCD BM的结构和功能异常引起的 造血血管和/或间充质壁龛；修复关键血管壁龛细胞缺陷将 提高HSPC植入率。干细胞动员也可能受到BM利基的影响，我们将寻求 了解干细胞如何在SCD中从骨髓渗出到血液中。因此，提出了三个测试目标 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.确定哪些壁龛缺陷通过输血而正常化，并确定BM生态位 3.确定骨髓壁龛缺陷与受损的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的造血方法。 在根治疗法的背景下植入。

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 Additional, unpublished preliminary data indicate that long-term (16 weeks) HSC reconstitution when transplanted into SCD mice is significantly compromised.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.