Engineering neural tissue using pluripotent stem cells

大脑和脊髓由不同种类的细胞组成。复制这些复杂的结构为我们提供了一个重要的机会来发现这些组织是如何在体内形成的。这种工程神经组织可以用于药理筛选的应用，而不是捐赠的人体组织。一种流行的组织工程策略是使用生物材料支架来传递信号，促进干细胞分化为神经组织。我的团队研究的是人类诱导多能干细胞（hiPSCs），成年细胞被重新编程成一种状态，在这种状态下，它们可以变成生物体中发现的任何类型的细胞。这种特性使它们成为组织工程的优秀细胞来源。我的团队确定了许多化学和物理线索，驱动hipsc向神经组织分化，这是本研究计划的起点。然而，目前使用hipsc工程神经组织的方法需要冗长且劳动密集型的协议。该研究项目的总体目标是通过开发生物活性支架，从hipsc中构建功能性神经组织，这些支架提供必要的化学和物理线索，以促进可转化为生物打印应用的快速分化。为了实现这一目标，本研究计划包括两个不同的目标，与目前的方法相比，本研究计划的结果将用于快速、高通量地生成神经组织。

Different kind of cells make up the brain and spinal cord. Replicating these complex structures provides us with a significant opportunity to discover how such tissues form in the body. Such engineered neural tissues can be used for applications in pharmacological screening instead of donated human tissues. One popular strategy for tissue engineering uses biomaterial scaffolds to deliver signals that promote stem cells to differentiate into neural tissue. My group works with human induced pluripotent stem cells (hiPSCs), adult cells reprogrammed into a state where they can become any type of cell found in an organism. This property makes them an excellent cell source for tissue engineering. My group identified a number of chemical and physical cues that drive the differentiation of hiPSCs into neural tissue, which serves as a starting point for this research program. However, current methods for engineering neural tissue using hiPSCs require lengthy, labor intensive protocols. The overarching goal of this research program is to engineer functional neural tissues from hiPSCs by developing bioactive scaffolds that present the necessary chemical and physical cues for promoting rapid differentiation that can be translated into bioprinting applications. This research program consists of two different aims for achieving this goal, and the results of this research program will be used to generate neural tissue in a rapid and high throughput manner compared to current methods. The first aim investigates how to modify the properties of 3D fibrin scaffolds so that they can generate functional neural tissue from hiPSCs. We can manipulate the mechanical properties of these scaffolds using cross-linking agents to increase their stability. We also can enhance their chemical properties by functionalizing them with bioactive cues like peptides that promote neuronal differentiation of hiPSCs. We will then determine the influence of these two types of cues on hiPSC differentiation by using these scaffolds as bioink for 3D printing of functional neural tissues. The second aim will elucidate how the controlled release of novel chemical cues from microspheres can rapidly differentiate hiPSCs into neurons. These chemical cues include the transcription factor Ascl1 (shown to efficiently produce neurons) functionalized with intracellular protein delivery technology, purmorphamine (shown to enhance motor neuron differentiation), and guggulsterone (shown to enhance dopaminergic neuron differentiation). Currently, no existing drug delivery systems can generate controlled release of these molecules all of which promote rapid differentiation of hiPSCs into neural tissue. We will demonstrate how different combinations and concentrations of these drug-releasing microspheres can be used to engineer two different types of neural tissue, which could then be used for drug screening applications.