Reversing Skeletal Aging by Restoring Functional Skeletal Stem Cell Diversity

通过恢复功能性骨骼干细胞多样性来逆转骨骼衰老

• 批准号: 10742457
• 负责人: Thomas Hans Ambrosi
• 金额: $ 24.9万
• 依托单位: UNIVERSITY OF CALIFORNIA AT DAVIS
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-04-01 至 2025-12-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10742457
• 关键词: Reversing; Skeletal; Aging; Restoring; Functional

Advancing age is tightly linked to the increasing global incidence of skeletal diseases. Osteoporosis poses a major public health threat for over 54 million Americans as it is interrelated with high fracture rates. Osteoporosis related hip fractures are invariably associated with significant morbidity and strikingly, a 58% mortality rate in the elderly within the first year of injury. This problem is compounded by a lack of efficient preventive and medical therapies for age-related bone disease free of major side effects. Recent studies have revealed adult stem cell populations within bone that could be potentially targeted as a regenerative source to maintain and restore skeletal health. However, breakthroughs in stem cell based-regenerative strategies have been hampered by the inability to isolate bona fide stem cell populations. Our group has helped delineate highly purified skeletal stem cell (SSC) lineages crucial for maintaining normal bone homeostasis and regeneration following injury. My latest results suggest that aging shifts lineage determination of stem cells triggering altered niche dynamics thereby contributing to a decline of regenerative capacity and providing a rationale that skeletal aging is caused by SSC dysfunction. The initial findings of this proposal provide evidence for the existence of multiple SSC subtypes (SSC diversity) present in limb long bones. Transcriptomic analysis at the single-cell level shows that SSCs undergo aging-induced molecular and compositional changes coinciding with functional heterogeneity. I have identified Wnt1 Inducible Signaling Pathway Protein 2 (Wisp2) that is specifically upregulated in the aged SSC lineage. Wisp2 significantly impairs bone formation when applied to SSC in vitro or fractures of young mice in vivo. Aim1 has determined the role of age-related changes in SSC diversity including the relative proportion of SSC subtypes and their functional heterogeneity to skeletal integrity and will now be completed with spatiotemporal single cell analysis to define anatomical changes of SSCs and their niche cell interactions. In Aim2, I will examine the mechanism of stem cell-based skeletal aging through Wisp2, which I hypothesize, may regulate SSC diversity and heterogeneity. Proposed experiments will also address the age-dependent role of stem cell based epigenetic drift and a potential connection to new concepts of stem cell aging such as adverse clonal skeletogenesis. Importantly, I will determine the unexplored identity of the Wisp2 receptor in SSCs by highly sensitive proximity-dependent labeling to identify targetable pathways involved in SSC-mediated skeletal aging. The guidance and research environment provided by my new host institution for my independent research phase is cutting-edge and highly relevant to the purpose of this proposal allowing implementation of the latest transcriptomic, epigenetic and proteomic methods, including single-cell RNA- and ATAC-sequencing, RNAScope, NanoString single cell imaging and TurboID, to interrogate the proposed aims. These studies will establish a new paradigm for understanding skeletal disease from the perspective of SSC diversity and should facilitate the development of new preventive, diagnostic, and therapeutic approaches to tackle skeletal disorders.

年龄的增长与全球骨骼疾病发病率的增加密切相关。骨质疏松症对超过5400万美国人构成了重大的公共健康威胁，因为它与高骨折率相关。骨质疏松相关的髋部骨折总是与显著的发病率相关，并且引人注目的是，在受伤的第一年内，老年人的死亡率为58%。这个问题由于缺乏有效的预防和药物治疗与年龄有关的骨疾病没有重大的副作用而变得更加复杂。最近的研究揭示了骨内的成体干细胞群，它们可能作为再生来源被靶向，以维持和恢复骨骼健康。然而，由于无法分离真正的干细胞群，基于干细胞的再生策略的突破受到阻碍。我们的团队已经帮助描绘了高度纯化的骨骼干细胞（SSC）谱系，这些谱系对于维持正常的骨稳态和损伤后的再生至关重要。我的最新研究结果表明，衰老改变了干细胞的谱系决定，触发了改变的生态位动态，从而导致再生能力下降，并提供了骨骼衰老是由SSC功能障碍引起的理论基础。该提案的初步发现为四肢长骨中存在多种SSC亚型（SSC多样性）提供了证据。单细胞水平的转录组学分析表明，精原干细胞经历衰老诱导的分子和组成的变化与功能异质性相一致。我已经确定了Wnt 1诱导信号通路蛋白2（Wisp2），它在老年SSC谱系中特异性上调。Wisp2在体外应用于SSC或在体内应用于年轻小鼠的骨折时显著损害骨形成。Aim1已经确定了年龄相关变化在SSC多样性中的作用，包括SSC亚型的相对比例及其对骨骼完整性的功能异质性，现在将通过时空单细胞分析来完成，以定义SSC的解剖学变化及其生态位细胞相互作用。在Aim2中，我将通过Wisp2研究基于干细胞的骨骼衰老机制，我假设Wisp2可能调节SSC的多样性和异质性。拟议的实验还将解决基于干细胞的表观遗传漂变的年龄依赖性作用，以及与干细胞衰老新概念的潜在联系，如不良克隆骨骼发生。重要的是，我将通过高度敏感的邻近依赖性标记来确定SSC中Wisp2受体的未探索身份，以确定参与SSC介导的骨骼衰老的靶向途径。我的新主办机构为我的独立研究阶段提供的指导和研究环境是尖端的，与本提案的目的高度相关，允许实施最新的转录组学，表观遗传学和蛋白质组学方法，包括单细胞RNA和ATAC测序，RNAScope，NanoString单细胞成像和TurboID，以询问拟议的目标。这些研究将从SSC多样性的角度为理解骨骼疾病建立一个新的范式，并应促进新的预防，诊断和治疗方法的发展，以解决骨骼疾病。