Dissecting in vitro models for toxicology

使用组织工程组织和器官作为动物试验的体外替代品正变得越来越重要，特别是在欧洲目前实施的消费品动物试验禁令(欧盟指令76/768/EEC)的背景下，这一禁令预计将在全球范围内推广。为了使体外试验模型标准化，必须注意确保每个“替代方案”不仅模仿作为目标的组织结构，而且共享关键的生化、形态、生理甚至遗传成分。组织工程方法利用天然生物材料的各种合成聚合物(有或没有额外的生物活性辅助因子)作为支架，创建合适的三维环境，细胞可以在这些环境上附着、增殖并分化为结构类似于自然组织的生理功能组织。然而，对“组织形态和结构”(支架)如何调节组织发育和功能的了解还比较缺乏，这使得模型之间的比较令人望而生畏，因为不同的组将根据他们选择的模型报告不同的安全性和有效性结果。我们的目标是剖析工程组织所涉及的发育机制，特别是生物材料作为支架在重建整个组织中的作用。我们将重点放在角膜作为试验台上，因为眼睛刺激性测试在工业中被广泛用于个人使用和家用消费品化合物的安全测试。简而言之，为了使事情易于处理，我们只关注在体外角膜组织工程中常用的生物材料来回答以下问题：作为支架的最佳材料类型是什么--惰性的、可降解的合成聚酯、惰性植物性纤维还是生物相互作用蛋白？或者，脚手架到底重要吗，或者它都是脚手架的机械性能或拓扑结构的优化？一旦我们确定了基本支架所需的基本特征，我们将利用这些知识来开发1)用于药效测试的体外疾病模型；以及2)用于安全/毒理学测试的完全合成的角膜模型。

The use of tissue engineered tissues and organs as in vitro alternatives to animal testing is gaining importance, especially in the context of the ban on animal testing for consumer products currently in place in Europe (EU Directive 76/768/EEC) which is expected to expand worldwide. To standardize in vitro models for testing, care must be taken to assure that each "alternative" not only mimics the tissue architecture as the target, but also shares key biochemical, morphological, physiological, and even genetic components. Tissue engineering methods utilize a wide range of synthetic polymers to natural biomaterials (with or without additional bioactive co-factors) as scaffolding to create appropriate 3-dimensional environments upon which cells can attach to proliferate and differentiate into physiologically functional tissues that are structurally similar to the native tissue. The understanding of how "tissue forms and architecture" (scaffolds) regulates tissue development and function, however, is somewhat lacking, making comparison amongst models daunting, as different groups will report different safety and efficacy results based on the model they have selected. Our objective is to dissect out the developmental mechanisms involved in engineering tissues, specifically the role of biomaterials as scaffolding used in reconstructing whole tissues. We focus on the cornea as a test bed since ocular irritancy testing is widely used in industry for safety testing of compounds for personal use and household consumer products. Very briefly, to keep things manageable, we focus only the biomaterials that are commonly used as scaffolding in in vitro corneal tissue engineering to answer the following questions: What is the best type of material for scaffolds - an inert, degradable synthetic polyester, an inert plant-based fibre or biointeractive protein? Or, does the scaffold matter at all, or it is all in optimization of the mechanical properties or topology of the scaffolding? Once we have identified the fundamental desired characteristics of the basic scaffold, we will use this knowledge to develop 1) an in vitro disease model for drug efficacy testing; and 2) a fully synthetic analog of a corneal model for safety/ toxicology testing.