An Artificial Perivascular Niche for Mesenchymal Stem Cells

描述（由申请人提供）：来自各种来源的干细胞具有巨大的潜力，可以彻底改变再生医学和了解疾病，但识别和操纵控制其命运的众多因素仍然是一个重大挑战。就出生后干细胞而言，生态位（定义为细胞所处的体内微环境）对命运决定的调节具有重要影响。在这个概念的基础上，一个特别令人兴奋的研究领域是人工干细胞龛的发展。目前最先进的人工生态位，通常涉及使用指导性生物材料作为2D和3D培养基质，已经产生了有希望的结果。然而，它们缺乏许多成体干细胞龛的一个关键解剖特征：靠近脉管系统。许多成体干细胞存在于体内脉管系统附近，包括神经干细胞、骨髓和脂肪组织中的间充质干细胞（MSCs）以及造血干细胞。鉴于这一解剖位置的保守性，我们假设在体外重建血管周围生态位可以调节、增强甚至恢复成体干细胞的多谱系潜力。本R21应用的目的是通过创建新的血管周围界面作为骨髓源性间充质干细胞的创新人工生态位，更深入地探索这一概念。我们的方法在逻辑上建立在我们发表的在体外3D水凝胶培养中产生强大的毛细血管网络的能力之上，我们的数据表明MSCs占据这些体外毛细血管网络中的血管周围位置。目的1将确定MSC与体外定义良好的毛细血管网络接触是否能维持其表达表明其多谱系潜力的表面标记物的能力。目的2将评估与培养扩增的间充质干细胞相比，与毛细血管接触是否能增强其多系分化潜力。最后，Aim 3将确定在人工血管周围生态位中培养老化的MSCs是否可以恢复其干细胞特性。从长远来看，成功实现这些拟议目标将产生两个重要的、或许会改变范式的潜在结果。首先，通过体外重建血管周围环境的关键特征，这里开创的工具和方法可能有助于阐明各种组织中的干细胞是如何在体内维持和指导的。其次，验证毛细血管网络具有指导意义（超越其滋养组织的能力）这一创新概念，将有可能使这一想法广泛扩展到各种临床/转化工作中，以再生组织。

DESCRIPTION (provided by applicant): Stem cells from a variety of sources hold enormous potential to revolutionize regenerative medicine and to understand disease, but identifying and manipulating the multitude of factors that control their fate remains a significant challenge. In the case of post-natal stem cells, the niche, defined as the in vivo microenvironment in which the cells reside, provides a significant influence on the regulation of fate decisions. Building on this concept, a particularly exciting area of research is the development of artificial stem cell niches. Current state-of-the-art artificial niches, which typically involve the use of instructive biomaterials as 2D and 3D culture substrates, have generated promising results. However, they lack a critical anatomic feature of many adult stem cell niches: proximity to the vasculature. Many adult stem cells reside near the vasculature in vivo, including neural stem cells, mesenchymal stem cells (MSCs) from bone marrow and adipose tissue, and hematopoietic stem cells. Given the conservation of this anatomic location, we hypothesize that recreating the perivascular niche ex vivo can regulate, enhance, and even restore the multilineage potential of adult stem cells. The objective of this R21 application is to explore this concept in more depth by creating a new perivascular interface as an innovative artificial niche for bone marrow-derived MSCs. Our approach builds logically on our published ability to generate robust capillary networks in vitro in 3D hydrogel-based cultures, and our data demonstrating that MSCs occupy perivascular locations in these in vitro capillary networks. Aim 1 will determine if MSC contact with a well-defined capillary network in vitro maintains their ability to express surface markers indicative of their multilineage potential. Aim 2 will assess if contact with capillary vessels enhances their multilineage differentiation potential when compared to culture-expanded MSCs. Finally, Aim 3 will determine if culturing aged MSCs within the artificial perivascular niche can restore their stem cell properties. Successful completion of these proposed aims would yield two important, perhaps paradigm- shifting, potential outcomes in the long run. First, by recreating key features of the perivascular environment ex vivo, the tools and approaches pioneered here could potentially help efforts to elucidate how stem cells in a variety of tissues are maintained and instructed within the body. Second, validating the innovative concept that capillary networks are instructive (beyond their ability to nourish tissues) will potentially enable broad expansion of this idea into a variety of clinical/translational efforts to regenerate tissues. PUBLIC HEALTH RELEVANCE: Many adult stem cells reside near blood vessels in the body. This project seeks to understand the significance and implications of that anatomic location, and to use this insight to develop a new method to control stem cell properties outside of the body. Understanding how blood vessels regulate stem cells, and using that knowledge to control their function provides the opportunity to impact bone regeneration strategies specifically, and any stem cell-based therapy more generally.