An Artificial Perivascular Niche for Mesenchymal Stem Cells

描述（由申请人提供）：各种来源的干细胞在彻底改变再生医学和理解疾病方面具有巨大潜力，但识别和操纵控制其命运的多种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在的体内微环境，对命运决定的调节具有重大影响。基于这一概念，一个特别令人兴奋的研究领域是人工干细胞生态位的开发。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生态位的一个关键解剖学特征：靠近脉管系统。许多成体干细胞位于体内脉管系统附近，包括神经干细胞、来自骨髓和脂肪组织的间充质干细胞（MSC）以及造血干细胞。鉴于这一解剖位置的保护，我们假设离体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。 R21 应用的目的是通过创建新的血管周围界面作为骨髓间充质干细胞的创新人工生态位，更深入地探索这一概念。我们的方法逻辑上建立在我们已发表的在基于 3D 水凝胶的培养物中体外生成强大的毛细血管网络的能力的基础上，并且我们的数据证明 MSC 在这些体外毛细血管网络中占据血管周围位置。目标 1 将确定 MSC 与体外明确的毛细血管网络接触是否保持其表达表明其多谱系潜力的表面标记的能力。目标 2 将评估与培养扩增的 MSC 相比，与毛细血管的接触是否会增强其多谱系分化潜力。最后，目标 3 将确定在人工血管周围微环境中培养老化的 MSC 是否可以恢复其干细胞特性。从长远来看，成功完成这些拟议目标将产生两个重要的、也许是范式转变的潜在成果。首先，通过离体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如何在体内维持和指导。其次，验证毛细血管网络具有指导意义（超出其滋养组织的能力）这一创新概念将有可能将该想法广泛扩展到各种组织再生的临床/转化工作中。 公共健康相关性：许多成体干细胞位于体内血管附近。该项目旨在了解该解剖位置的重要性和影响，并利用这种见解开发一种新方法来控制体外干细胞的特性。了解血管如何调节干细胞，并利用这些知识来控制其功能，为具体影响骨再生策略以及更广泛的任何基于干细胞的治疗提供了机会。

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.