How Does a Young Extracellular Matrix Rejuvenate Old Mesenchymal Stem Cells?

描述（由申请人提供）： 骨髓间充质干细胞（MSCs）具有自我更新和分化为多种细胞系的能力。由于这些能力，MSC在大多数组织类型的持续维护和修复中发挥重要作用。随着年龄的增长，骨髓间充质干细胞的数量和质量下降，这反过来又与组织和器官功能的进行性衰竭有关。最近，我们报道了在小鼠中，老年间充质干细胞的自我更新和骨形成能力的缺陷完全恢复暴露于细胞外基质（ECM）由骨髓基质细胞从年轻的动物，这种改善大大减少时，细胞（无论是年轻或年老的小鼠）培养ECM由年老的骨髓基质细胞。这促使我们研究这种现象是否也发生在人类身上。事实上，我们在人类受试者中的初步研究清楚地表明，在由年轻骨髓基质细胞制成的ECM上培养老年MSC能够提高其数量和质量。该建议的目标是确定年轻ECM使老骨髓源性MSC恢复活力的机制。一个独特的，无细胞ECM模型将用于解剖年轻ECM如何在体外和体内恢复老MSC的功能。在本申请中提出的假设是，年龄对通常保留MSC功能的ECM的形成产生负面影响，并且通过暴露于由来自年轻供体的基质细胞制成的ECM，可以改善老年MSC的数量和质量。我们非常有能力在人类中测试这一假设，因为除了我们强大的初步数据外，在过去三年中已经从老年人（60至96岁）中积累了多达100份人类骨髓样本。为了验证这一假设，我们将系统地评估在年轻或老年ECM上维持的年轻与老年MSC的体外和体内生物活性（具体目标1），并对暴露于年轻或老年ECM的年轻和老年MSC进行蛋白质组学分析，以阐明与被拯救细胞的恢复功能相关的蛋白质水平的潜在变化（具体目标2）。为了充分理解MSC行为影响的潜在机制，我们将确定年轻与老年ECM结构的差异，包括结构、机械特性和蛋白质组成（具体目标3）。这些研究是创新的，因为我们将首次建立一个独特的体外人类模型来研究年龄对MSC的影响（内在理论），以及周围ECM对MSC的变化（外在理论）。从转化的角度来看，我们的研究是重要的，因为它们将提供关键信息，可以促进使用患者自己的（自体）干细胞进行基于细胞的治疗。鉴于老年人是这种类型治疗的主要目标人群，低估MSC和宿主中与年龄相关的变化对于改善老年退伍军人移植自体MSC的临床结果至关重要。

DESCRIPTION (provided by applicant): Bone marrow-derived mesenchymal stem cells (MSCs) are capable of self-renewal and differentiation into multiple cell lineages. Because of these capabilities, MSCs play an important role in continuous maintenance and repair of most tissue types. The quantity and quality of MSCs decrease with aging, which, in turn, is associated with the progressive failure of function of tissues and organs. Recently, we reported in mice that defects in the self-renewal and bone formation capacity of aged MSCs were completely restored by exposure to extracellular matrix (ECM) made by marrow stromal cells from young animals, and such improvement was substantially diminished when cells (from either young or old mice) were cultured on ECM made by old marrow stromal cells. This led us to investigate whether this phenomenon also occurs in humans. Indeed, our preliminary studies in human subjects clearly suggest that culturing aged MSCs on ECM made by young marrow stromal cells is able to improve their number and quality. The goal of this proposal is to determine the mechanisms whereby young ECM rejuvenates old bone marrow-derived MSCs. A unique, cell-free ECM model will be used to dissect how young ECM restores the functions of old MSCs in vitro and in vivo. The hypothesis proposed in this application is that age negatively impacts the formation of an ECM that normally preserves MSC function, and the quantity and quality of aged MSCs can be improved by exposure to an ECM made by stromal cells from young donors. We are uniquely-positioned to test this hypothesis in humans since, in addition to our strong preliminary data, up to 100 human bone marrow samples have been accumulated in the past three years from elders (60 to 96 years old). To test this hypothesis, we will systematically evaluate biological activities in viro and in vivo of young vs. old MSCs maintained on young- or old-ECM (Specific aim 1), and conduct proteomic analysis of young- and old-MSCs exposed to young- or old-ECM to elucidate the underlying changes at the protein level that are associated with the restored functions of the rescued cells (Specific aim 2). To fully understand the mechanisms underlying the influence of MSC behavior, we will determine the differences in the structures of young- vs. old-ECM including the architecture, mechanical properties, and protein composition (Specific aim 3). These studies are innovative in that we will have established, for the first time, a unique in vitr human model to examine effects of age on MSCs (intrinsic theory), and changes to MSCs by the surrounding ECM (extrinsic theory). Our studies are important from a translational point of view because they will provide key information that can facilitate the use of a patient's own (autologous) stem cells for cell- based therapies. In view of the fact that the elderly are the mai target population for this type of treatment, understating age-related changes in both MSCs and host is essential for improving the clinical outcome of transplanted autologous MSCs in old veteran.