Mechanosensitive synthetic cell-regulatable hydrogels for tissue engineering

摘要 非常需要工程化的功能组织来解决目前未满足的医疗需求， 或修复因疾病、损伤和先天性缺陷而受损的组织和器官。生物材料 支架可以在组织工程中发挥关键作用，因为它们不仅提供机械支撑， 递送生物活性分子和/或细胞，但它们也降解以提供新的空间来支持细胞生长， 细胞外基质产生。理想的是支架与新组织的速率一致地降解 阵支架降解也动态地影响其机械性能，这已被证明是 调节宿主和移植细胞的行为，如铺展、增殖、迁移和分化。 尽管已经尝试预测和定制所用的可生物降解的聚乙烯的降解速率， 由于在植入之前支架用于特定的组织再生应用，目前难以控制它们的 植入后降解。以触发方式调节支架降解，外源性或外部 已经使用了刺激，例如酶、pH和光。很少有人认为力是触发输入。 生物化学分子，如宿主/移植细胞分泌的酶，已经有报道 以控制生物材料支架的降解速率。然而，在以下方面仍然存在挑战： 以匹配支架降解所需的速率和水平调节这些分子的产生量 在提供最小的机械支撑损失的同时，因此，我们认为， 通过组织工程支架对机械强度的响应动态调节其降解 环境可以允许设计智能生物材料，当新形成的组织能够 支持所需的负载。一种合成生物学方法来创建机械敏感的合成细胞（MSSC） 具有机械敏感性通道，用于模拟细胞分泌生化物质的能力， 提出了响应于环境机械信号降解生物材料支架。合成细胞是 细胞大小的脂质双层囊泡包封表达感兴趣蛋白质的无细胞表达系统。 将创建装载不同大小货物的MSSC，并使其能够在以下条件下释放有效载荷 将检查压缩应力（目标1）。然后将MSSC包封在水凝胶系统中， 检查外部压缩应力介导的有效载荷从MSSC释放以调节 水凝胶降解（目标2）。最后，外部压缩应力控制的水凝胶的能力 将检查在驱动水凝胶共包封的细胞的功能中的降解（目的3）。这项工作将 创造了一类新的水凝胶，具有独特的机械响应机制， 它们的物理环境，并预计是有价值的工程广泛的组织。

Abstract There is great need for engineered functional tissues to address currently unmet medical need for replacement or restoration of damaged tissues and organs due to disease, injury and congenital defects. Biomaterial scaffolds can play a key role in engineering tissues because they not only provide mechanical support and deliver bioactive molecules and/or cells, but they also degrade to provide new space to support cell growth and extracellular matrix production. It is desirable for the scaffold to degrade in concert with the rate of new tissue formation. Scaffold degradation also dynamically affects its mechanical properties, which has been shown to regulate host and transplanted cell behaviors, such as spreading, proliferation, migration and differentiation. Although attempts have been made to predict and tailor the degradation rate of employed biodegradable scaffolds prior to implantation for specific tissue regeneration applications, it is currently difficult to control their degradation after implantation. To regulate scaffold degradation in a triggered fashion, exogenous or external stimuli, such as enzymes, pH, and light, have been employed. Few have considered forces as a trigger input. Biochemical molecules, such as enzymes secreted from hosted/transplanted cells, have already been reported in efforts to control the degradation rate of biomaterial scaffolds. However, there are still challenges regarding regulating the production amount of those molecules at a rate and level needed to match scaffold degradation profile with engineered tissue formation while providing a minimal loss in mechanical support. Therefore, dynamic regulation of the degradation of a tissue engineering scaffold via its response to its mechanical environment may allow for design of smart biomaterials that resorb as the newly formed tissue is able to support the required loads. A synthetic biology approach to create mechanosensitive synthetic cells (MSSCs) harboring mechanosensitive channels for mimicking the ability of cells to secrete biochemicals for dynamically degrading biomaterial scaffolds in response to environment mechanical signals is proposed. Synthetic cells are cell-sized lipid bilayer vesicles encapsulating cell-free expression system expressing proteins of interest. MSSCs loaded with different sized cargos will be created and their capability to release the payloads under compressive stress will be examined (Aim 1). The MSSCs will then be encapsulated in a hydrogel system for examining the capacity of external compressive stress-mediated payload release from MSSCs to regulate hydrogel degradation (Aim 2). Lastly, the capacity of external compressive stress-controlled hydrogel degradation in driving the function of hydrogel co-encapsulated cells will be examined (Aim 3). This work will create a new class of hydrogels with a distinct mechanism of mechanoresponsiveness that dynamically react to their physical environment and are anticipated to be valuable for engineering a wide range of tissues.