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

项目总结 很有必要开发预防和治疗方案来延缓衰老 过程，以恢复组织/器官的活力，并加强再生和修复。血液系统的老化是 与血管完整性的丧失和造血干细胞(HSC)功能的急剧变化有关。在……里面 除了数量增加和丧失自我更新能力外，陈旧的造血干细胞还表现出髓系偏向和 有发展成血液系统恶性肿瘤的倾向。虽然其中一些变化反映了细胞内在的变化， 新出现的证据表明，其中一些缺陷也可能受到骨髓(BM)的调节。 微环境，特别是骨髓内皮细胞的生态位。特别是，我们已经证明了BM 内皮细胞生态位对于维持HSC自我更新和分化之间的平衡是不可或缺的 在清髓侮辱之后。我们还发现在骨髓内皮细胞(BMECs)中AKT/mTOR信号转导。 是维护HSC所必需的，并且该信令在老化的BMEC中被中断。要问一问如何 内皮细胞中AKT/mTOR信号轴的破坏会影响造血系统，我们有条件地 在成年ECs(mTOR(ECKO)小鼠)中缺失mTOR，并发现该缺失导致 HSCs的表型、功能和转录分析表明。为了更好地了解如何 EC介导的信号驱动造血系统的衰老，我们利用我们的mTOR(ECKO)小鼠模型 作为一种筛查工具，以发现尚不清楚的促HSC衰老因素。转录组和蛋白质组学研究 发现血栓反应蛋白-1(TSP1)是一种候选的促衰老因子，通常在 MTOR(ECKO)和衰老小鼠与年轻对照组比较。此外，TSP1的全球敲除导致 老年小鼠肝星状细胞功能的保存与复壮。这项研究提案旨在测试 这是可能的：1)逆转与年龄有关的表型的造血和血管系统通过全球或 TSP1的细胞特异性缺失，或抗体介导的抑制，2)增强体外扩增和功能 通过外源性抑制TSP1抑制衰老的HSC，以及3)使衰老的骨髓微环境恢复活力 应用年轻的骨髓微血管内皮细胞作为细胞治疗药物联合或不联合输注治疗骨髓抑制 抗TSP1的中和抗体。拟议的研究将利用开发的新的体内和体外模型。 如果成功，将释放抑制TSP1的治疗潜力，以改善整体健康寿命， 延年益寿，促进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，旨在有效地 逆转与年龄相关的造血功能缺陷的手段。

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.