Engineering Polymers to Control Cell Fate

我们的首要目标是设计聚合物来控制细胞的命运。利用创新的生物材料科学和工程战略，我们正在解决细胞生物学中的一些最大问题。例如，几十年来，细胞一直在组织培养聚苯乙烯平板--坚硬的塑料表面--培养，这种表面很难模拟细胞在体内的生长、分裂和分化。其结果是，无论是理解基本现象还是筛选分析，体外研究都不能很好地预测体内结果。因此，虽然传统的2D细胞培养已经取得了重大进展，但问题是也错过了重大进展。社区已经认识到需要在更仿生的环境中培养细胞--一种模拟正常组织的化学、物理和机械特性的环境--这样我们就可以在实验室中概括细胞的生长情况。关键问题是如何在实验室中培养组织。我们的基本目标是设计聚合物水凝胶支架，在其中引导细胞生长和分化，以便在实验室中创造组织模拟。创新在于聚合物科学--结果在于细胞反应。这一平台策略可以适用于多种细胞类型；在此，我们将主要关注中枢神经系统的细胞，并研究细胞外基质与神经元和胶质细胞之间的密切作用，以创建仿生神经组织。与此同时，我们建议使用生物工程策略来解决干细胞生物学中的另一大挑战--即如何确保细胞在移植后的存活和整合。干细胞通常被注射在生理盐水中，通常会在不久之后死亡和分散。对于中枢神经系统，细胞需要整合到神经回路中，为此它们需要生存。在促进生存的微环境中提供细胞可以解决这一关键挑战。我们的基本目标是设计一种具有这样一个定义的微环境的可注射给药系统。亲和力释放是一种实现生物活性分子控制释放的新兴方法，但主要是用肝素为基础的材料来探索的，其中蛋白质-肝素相互作用控制释放，并且固有地限于肝素结合的生长因子。为了设计一种受控亲和释放的平台策略，我们建议利用非共价的、特定的相互作用来调节生物活性蛋白的释放。通过控制结合/解离的速率常数，这种类似魔术贴的系统能够控制蛋白质的释放。我们建议控制两种生物活性因子以不同的速度同时释放--这是以前从未探索过的--最终目标是提高细胞存活率。这一创新策略广泛适用于多种材料和蛋白质，并将通过两种影响视网膜干细胞存活的因素和一种水凝胶进行测试，水凝胶本身对悬浮在其中的细胞具有促进生存的作用。我们正在利用先进的聚合物科学为生物问题提供工程解决方案。在这项提议中，我们既提高了加拿大的知识水平，又培养了加拿大关键优势领域的高素质人才。我的HQP培训记录非常出色--在我的实验室接受培训的115名HQP后来在学术界、工业界和政府担任领导职务。我们在影响力很大的期刊上发表文章，为新发明申请专利，在国际会议上发表演讲，与学术界和工业界的世界领袖合作，并向政府提供建议。

Our overarching goal is to engineer polymers to control cell fate. Using innovative biomaterials science and engineering strategies, we are tackling some of the biggest questions in cell biology. For example, for decades cells have been cultured in tissue culture polystyrene plates – hard, plastic surfaces – that poorly mimic how cells grow, divide, differentiate in vivo. The consequence is that in vitro studies are poor predictors of in vivo outcomes, whether to understand fundamental phenomena or screening assays. Thus, while significant advances have been achieved with traditional 2D cell culture, the problem is significant advances have also been missed. The community has recognized the need to grow cells in a more biomimetic environment – one that mimics the chemical, physical, mechanical properties of normal tissue – so that we can recapitulate cell growth in the laboratory. The key question is how to grow tissues in the lab. Our underlying goal is to design polymeric hydrogel scaffolds in which to guide cell growth and differentiation in order to create tissue mimetics in the laboratory. The innovation is in the polymer science – the outcome is in the cellular response. This platform strategy can be adapted for multiple cell types; herein, we will focus primarily on cells of the central nervous system and investigate the intimate role of the extracellular matrix with neurons and glia to create biomimetic neural tissues. At the same time, we propose to tackle another big challenge in stem cell biology using bioengineering strategies – that is, how to ensure cell survival and integration after transplantation. Stem cells are typically injected in saline and typically die and disperse soon afterwards. For the central nervous system, cells need to integrate into the neural circuitry and for this they need to survive. Delivering cells in a microenvironment that promotes survival addresses this key challenge. Our underlying goal is to design an injectable delivery system with such a defined microenvironment. Affinity-based release is an emerging approach to achieve controlled release of bioactive molecules, but has been primarily explored with heparin-based materials where the protein-heparin interaction controls release and is inherently limited to heparin-binding growth factors. In order to design a platform strategy for controlled affinity release, we propose to take advantage of non-covalent, specific interactions to modulate the release of bioactive proteins. By controlling the rate constants of association/dissociation, this “Velcro-like” system enables controlled release of proteins. We propose to control the simultaneous release of two bioactive factors, at different rates - something that has not been previously explored – with the ultimate goal of enhancing cell survival. This innovative strategy is broadly applicable to multiple materials and proteins and will be tested with two factors that influence retinal stem cell survival and a hydrogel, which itself has a pro-survival effect on the cells suspended within. We are engineering solutions to biological questions using advanced polymer science. In this proposal, we both advance knowledge and train high quality personnel in key areas of strength for Canada. My record of HQP training is exceptional – the 115 HQP trained in my laboratory have gone on to pursue leadership positions in academia, industry and government. We publish in high impact journals, patent new inventions, present at international conferences, collaborate with world leaders in academia and industry, and provide advice to government.