Rejuvenation of aged hematopoietic stem cells and endothelial niches by thrombospondin-1 blockade

项目摘要 存在对于开发预防和治疗选择以延缓衰老的实质性需求。 过程，使组织/器官恢复活力，并增强再生和修复。血液系统的老化是 与血管完整性的丧失和造血干细胞（HSC）功能的显著变化相关。在 除了数量增加和失去自我更新能力外，老年HSC表现出髓样偏向， 发展血液恶性肿瘤的倾向。虽然其中一些变化反映了细胞内在的改变， 新出现的证据表明，这些缺陷中的一些也可能受到骨髓（BM）的调节， 微环境，特别是BM内皮生态位。特别是，我们已经证明，BM 内皮生态位对于支持HSC自我更新和分化之间的平衡是不可或缺的 清髓性损伤后死亡我们还表明，骨髓内皮细胞（BMEC）中的AKT/mTOR信号转导 是维持HSC所必需的，并且这种信号传导在老化的BMEC中被破坏。要问一个 内皮细胞中AKT/mTOR信号轴的破坏影响造血系统，我们有条件地 在成年EC（mTOR（ECKO）小鼠）中删除mTOR，并发现这种缺失导致 HSC通过其表型、功能和转录分析证明。更好地了解如何 EC介导的信号传导驱动造血系统的老化，我们利用我们的mTOR（ECKO）小鼠模型 作为一种筛选工具，以发现未知的促HSC老化因子。转录组学和蛋白质组学研究 将血小板反应蛋白-1（TSP 1）鉴定为一种候选促衰老因子， mTOR（ECKO）和老年小鼠与年轻对照相比。此外，TSP 1的全局敲除导致 老年小鼠HSC功能的保存和再生。这项研究旨在测试是否 有可能：1）通过整体或局部逆转造血和血管系统的年龄相关表型， TSP 1的细胞特异性缺失或抗体介导的抑制，2）增强离体扩增和功能 通过外源性抑制TSP 1使老化的HSC恢复活力，以及3）使老化的BM微环境在 通过利用年轻的BMEC作为细胞治疗剂进行骨髓抑制治疗，有或没有共输注 TSP 1的中和抗体拟议的研究将利用开发的新型体内和体外模型 如果成功的话，将释放TSP 1抑制的治疗潜力，以改善整体健康状况， 长寿，以及老年人造血系统的再生。这项研究计划的成功 将为开发广泛的治疗策略开辟新的途径， 逆转与年龄相关的造血缺陷的方法。

PROJECT SUMMARY There is a substantial need for the development of preventative and therapeutic options to delay the aging process, to rejuvenate tissue/organs, and to enhance regeneration and repair. Aging of the blood system is associated with loss of vascular integrity and dramatic changes in hematopoietic stem cell (HSC) function. In addition to increasing in number and losing self-renewal potential, old HSCs exhibit a myeloid bias and increased propensity to develop hematologic malignancies. While some of these changes reflect cell-intrinsic alterations, emerging evidence suggests that some of these defects may also be regulated by the bone marrow (BM) microenvironment, in particular the BM endothelial niche. In particular, we have demonstrated that the BM endothelial niche is indispensable for supporting the balance between HSC self-renewal and differentiation following myeloablative insult. We have also shown that AKT/mTOR signaling in BM endothelial cells (BMECs) is required for maintenance of the HSCs and that this signaling is disrupted in aged BMECs. To ask how a disruption of the AKT/mTOR signaling axis in ECs affects the hematopoietic system, we have conditionally deleted mTOR in adult ECs (mTOR(ECKO) mice) and found that this deletion resulted in the premature aging of HSCs as demonstrated by their phenotypic, functional, and transcriptional analysis. To better understand how EC-mediated signaling drives the aging of the hematopoietic system, we utilized our mTOR(ECKO) mouse model as a screening tool to discover as yet unknown pro-HSC-aging factors. Transcriptomic and proteomic studies identified Thrombospondin-1 (TSP1) as a candidate pro-aging factor that was commonly upregulated in mTOR(ECKO) and aged mice when compared to young controls. Moreover, global knockout of TSP1 resulted in preservation and rejuvenation of HSC function in aged mice. This research proposal is designed to test whether it is possible to: 1) reverse the age-related phenotypes of the hematopoietic and vascular systems by global or cell-specific deletion, or antibody-mediated inhibition, of TSP1, 2) enhance the ex vivo expansion and function of aged HSC by exogenous inhibition of TSP1, and 3) rejuvenate an aged BM microenvironment following myelosuppressive treatments by utilizing young BMECs as a cellular therapeutic with or without the co-infusion of a neutralizing antibody to TSP1. The proposed studies will utilize novel in vivo and in vitro models developed in our lab and, if successful, will unlock the therapeutic potential of TSP1 inhibition to improve overall healthspan, longevity, and regeneration of the hematopoietic system in the elderly. The success of this research proposal will open up new avenues for the development of a wide array of therapeutic strategies designed as an effective means to reverse age-related hematopoietic deficiencies.