An iPSC based xeno-free platform to assess the foreign body response against new biomaterials

植入式生物材料和医疗器械已经成为各种健康问题的主流解决方案，其应用也在不断增加。然而，这些设备中使用的材料可能被免疫系统视为外来物，引发可能伤害患者并停止设备工作的不良免疫反应。这些反应（通常称为异物反应或FBR）是由血液中循环的免疫细胞（如T细胞和单核细胞）和那些驻留在植入装置的组织中的免疫细胞（如巨噬细胞）发起的。巨噬细胞攻击植入物，试图将其从体内清除，这会导致并发症，包括炎症和围绕植入物的致密组织（纤维化胶囊）的形成。这些并发症是矫正手术的主要原因，每年给卫生系统造成数十亿美元的损失，并给数百万患者造成严重痛苦。因此，人们对研究FBR用于新生物材料非常感兴趣，然而，不幸的是，在生物材料的发现管道中，每年有成千上万的动物用于学术界和工业界，这严重依赖于动物模型。除了伦理问题外，这些模型价格昂贵，而且与人类的生理相关性较差，尤其是由于人类和动物的免疫系统存在根本差异。因此，开发更好的体外模型来研究FBR是一个尚未满足的需求。为了满足这一需求，我们将建立一个基于干细胞的微流控装置，可以模拟FBR，并用于测试新的生物材料与植入的兼容性。我们将通过4个相互关联的任务来实现这一目标：任务1：开发免疫细胞和基质细胞的无xeno hIPSC分化。我们已经开发并验证了一种高效的无xeno干细胞分化平台，可以在单一培养基中创建我们模型所需的所有必要细胞类型（内皮细胞、成纤维细胞、巨噬细胞和t细胞），并将在我们的无xeno系统中完成t细胞的开发。任务2：优化不同细胞类型和细胞供应的静态共培养。我们的分化平台是基于单一细胞培养基的所有细胞类型，使不同细胞类型的共培养更简单。我们将以反映健康人体组织的比例混合不同类型的细胞，并评估细胞代谢、增殖、死亡和炎症概况的基线水平。任务3：微流控平台组装和优化。我们将构建包含复制血管网络、基质组织和模拟血流的泵的微流体装置。我们将进一步优化设备的长期细胞功能，以实现至少2周的功能寿命。任务4：在新平台中使用选择特性良好的生物材料进行验证。我们将通过研究FBR与临床相关生物材料的选择来比较新平台的性能，我们可以从成熟的动物模型中获得现有的体内数据。这将使我们能够微调新设备的不同方面（单元数，定量，流量），以优化设备性能（如果需要的话）。总之，这些目标将提供一个基于干细胞的微流控FBR模型，该模型将概括目标组织的三维性和对植入装置的免疫反应中发生的动态事件，包括循环免疫细胞向植入部位的募集，免疫细胞通过血管和结缔组织的迁移以及它们与局部区域其他细胞的相互作用。该模型将不依赖于原代细胞类型/供体，因此减少了平台的可变性。最终，这将允许更准确的生物材料发现，同时取代每年使用数万只动物进行生物材料测试的需要。

Implantable biomaterials and medical devices have become mainstream solutions for a variety of health problems and their use is constantly increasing. However, the materials used in these devices can be seen as foreign by the immune system triggering adverse immune reactions that could harm the patient and stop the device from working. These responses (generally known as foreign body response or FBR) are initiated by immune cells circulating in the blood (e.g. T cells and monocytes) and those that are resident (e.g. macrophages) in the tissues where the devices are implanted. Macrophages attack implants in an attempt to clear them from the body which leads to complications including inflammation and formation of dense tissues (fibrotic capsules) that surround the devices. Such complications are major causes of corrective surgeries costing the health system billions annually and causing significant suffering for millions of patients. There is therefore significant interest in investigating FBR for new biomaterials, unfortunately however, there is a heavy reliance on animal models in the biomaterials discovery pipeline with thousands of animals used in both academia and industry each year. In addition to ethical issues, these models are expensive, and have poor physiological relevance to human not least due to fundamental differences between the immune system in humans and the animals. Thus, there is an unmet need for developing better in vitro models to investigate FBR.To address this need we will build a stem cell based, microfluidic device that can model the FBR and be used to test new biomaterials for compatibility with implantation. We will achieve this via 4 interlinked tasks:Task 1: Development of Xeno-free hIPSC differentiation of immune and stromal cells. We have developed and validated an efficient, xeno-free stem cell differentiation platform to create all of the necessary cell types required for our model (endothelium, fibroblasts, macrophages and T-cells) in a single media and will finalise development of T-cells in our xeno-free system. Task 2: Optimising static co-cultures of different cell types and cell supply. Our differentiation platform is based on a single cell culture media for all cell types making coculture of the different cell types more simplified. We will mix different cell types together at ratios that reflect healthy human tissue and assess baseline levels of cell metabolism, proliferation, death and inflammatory profiles. Task 3: Microfluidic platform assembly and optimisation. We will build the microfluidic device containing compartments replicating vascular networks, stromal tissue and pumps simulating blood flow. We will further optimise long term cellular function of the device to achieve a functional life span of at least 2 weeks. Task 4: Validation of in the new platform using a selection of well characterised biomaterials. We will compare the performance of the new platform by investigating FBR to a selection of clinically relevant biomaterials where we have access to existing in vivo data from well established animal models. This will enable us to fine tune different aspects of the new device (cell numbers, rations, flow rates) to optimise the device performance if necessary. Together these objectives will deliver a stem cell based, microfluidic FBR model that will recapitulate the three-dimensionality of the target tissue and the dynamic events occurring in immune responses to implanted devices, including recruitment of circulating immune cells to the site of the implant, immune cell migration through blood vessels and connective tissues and their interactions with other cells in the local area. The model will not be reliant on primary cell types/donors and therefore reduce variability of the platform. Ultimately, this will allow more accurate biomaterial discovery while replacing the need to use tens of thousands of animals per year in biomaterial testing.