Unveiling comprehensive cellular biophysical properties using quantitative phase digital holographic microscopy

人类大脑的发育表现出物种特有的特征，特别是产生被认为是人类特有认知能力核心的结构，如大脑皮层。然而，这种神经发育和导致这种复杂性的具体机制仍然不完全清楚，主要是因为人类胚胎大脑的实验可及性很差。然而，最近基于多能干细胞(PSCs)的技术的发展已经允许从例如健康志愿者的简单皮肤活检中产生组成他/她的组织的所有类型的细胞，包括构成脑组织的神经细胞。考虑到PSCs在许多方面概括了胚胎神经元的发育过程，其准确的研究为分析人脑发育提供了独特的新机会。更好地理解使用PSCs技术建立人脑体外发育模型是我们在加拿大卓越神经光子学研究主席(CERC)框架内实现的研究计划的主要目标。为此，我们一直在开发新的多模式光学显微镜技术，能够准确和非侵入性地显示PSC分化为人类成熟和功能神经元过程中的细胞结构和动力学。具体地说，由于这一研究计划，我们计划开发基于全息原理的多模式光学显微镜技术，不仅具有三维可视化活细胞的能力，还可以同时提供细胞生物物理和生物化学的信息。事实上，最近来自多个领域的研究表明，物理力量和生物力学细胞属性在控制细胞和组织发育方面发挥着与化学物质和基因一样重要的作用。实际上，使用这种新的多模式全息显微镜技术将有可能具体解决与胚胎神经元成熟为功能神经元相关的细胞生物物理性质的测量问题。此外，这种多模式能力允许同时掌握多方面生物过程的几个方面，代表了一种有希望的方法，以更全面地了解从PSC产生功能神经元的基本机制。我们的研究计划，在光学、光子学和神经生物学之间的接口，主要培养物理学家、工程师、数学家和生物学家，他们结合他们的知识和技能，促进我们对使用PSCs的人脑发育基本机制的理解，并改进我们推进细胞成像的方法。

The human brain development displays species-specific features, in particular to generate the structures thought to be at the core of human-specific cognitive abilities, such as the cerebral cortex. However, the specific mechanisms underlying this neurodevelopment and leading to this complexity remain incompletely understood, primarily because of the poor experimental accessibility of the human embryonic brain. Nevertheless, recently, the development of technologies based on pluripotent stem cells (PSCs) have permitted to generate, from e.g. a simple skin biopsy of a healthy volunteer, all cell types that comprise his/her tissue including neuronal cells, which constitute the brain tissue. Considering that such generation process of human neuronal cells from PSCs in many ways recapitulates the development of embryonic neurons, its accurate study is providing unique new opportunities for the analysis of human brain development.Obtaining a better understanding of this modeling human brain development in-vitro using PSCs technology represents the main objective of our research program achieved within the framework of the Canada Excellence Research Chair (CERC) in Neurophotonics. Toward this aim, we have been developing new multimodal optical microscopy techniques having the capacity to visualize accurately and non-invasively cells structure and dynamics during the generation process of human mature and functional neurons from PSCs.Specifically, thanks to this research program, we plan to develop multimodal optical microscopy techniques, based on a holographic principle, having not only the capacity to visualize living cells in 3D but also to simultaneously provide information about cell biophysics and biochemistry. Indeed, recent work from a variety of fields has revealed that physical forces and biomechanical cell properties play as important a role in control of cell and tissue development as chemicals and genes. Practically, using such novel multimodal holographic microscopy techniques will make possible to address specifically questions concerning the measurement of cell biophysical properties in relation with the maturation of embryonic neurons into functional neurons. In addition, this multimodal capacity allowing grasping simultaneously several aspects of the multifaceted biological processes represents a promising approach to obtain a more comprehensive understanding of the basic mechanisms underlying the generation of functional neurons from PSCs.Our research program, at the interface between optics, photonics and neurobiology mainly trains physicists, engineers, mathematicians and biologists, who combine their knowledge and skills to advance our understanding of the basic mechanisms of human brain development using PSCs and to improve our methods for advancing cell imaging.