Vo Thanh, Shah Sameer B, Choy John S, Luo Xiaolong
Department of Mechanical Engineering, The Catholic University of America, Washington, D.C. 20064, USA.
Department of Biology, The Catholic University of America, Washington, D.C. 20064, USA.
Biomicrofluidics. 2020 Jan 17;14(1):014108. doi: 10.1063/1.5128739. eCollection 2020 Jan.
Chemotropism is an essential response of organisms to external chemical gradients that direct the growth of cells toward the gradient source. Chemotropic responses between single cells have been studied using gradients of synthetically derived signaling molecules and helped to develop a better understanding of chemotropism in multiple organisms. However, dynamic changes including spatial changes to the gradient as well as fluctuations in levels of cell generated signaling molecules can result in the redirection of chemotropic responses, which can be difficult to model with synthetic peptides and single cells. An experimental system that brings together populations of cells to monitor the population-scale chemotropic responses yet retain single cell spatiotemporal resolution would be useful to further inform on models of chemotropism. Here, we describe a microfluidic platform that can measure the chemotropic response between populations of mating yeast A- and α-cells with spatiotemporal programmability and sensitivity by positioning cell populations side by side in calcium alginate hydrogels along semipermeable membranes with micrometer spatial control. The mating phenotypes of the yeast populations were clearly observed over hours. Three distinct responses were observed depending on the distance between the A- and α-cell populations: the cells either continued to divide, arrest, and develop a stereotypical polarized projection termed a "shmoo" toward the cells of opposite mating type or formed shmoos in random directions. The results from our studies of yeast mating suggest that the biofabricated microfluidic platform can be adopted to study population-scale, spatial-sensitive cell-cell signaling behaviors that would be challenging using conventional approaches.
向化性是生物体对外部化学梯度的一种基本反应，该梯度引导细胞朝着梯度源生长。利用合成衍生信号分子的梯度对单细胞之间的向化性反应进行了研究，这有助于更好地理解多种生物体中的向化性。然而，包括梯度的空间变化以及细胞产生的信号分子水平的波动在内的动态变化，可能导致向化性反应的重新定向，而这用合成肽和单细胞很难进行建模。一个能够将细胞群体聚集在一起以监测群体规模的向化性反应，同时又能保持单细胞时空分辨率的实验系统，将有助于进一步完善向化性模型。在此，我们描述了一种微流控平台，该平台通过在半透膜上以微米级空间控制将细胞群体并排放置于海藻酸钙水凝胶中，能够以时空可编程性和灵敏度测量交配型酵母A细胞和α细胞群体之间的向化性反应。数小时内可清晰观察到酵母群体的交配表型。根据A细胞和α细胞群体之间的距离，观察到三种不同的反应：细胞要么继续分裂、停滞，并朝着相反交配型的细胞形成一种称为“shmoo”的典型极化突起，要么随机方向形成shmoo。我们对酵母交配的研究结果表明，这种生物制造的微流控平台可用于研究群体规模、空间敏感的细胞间信号传导行为，而使用传统方法进行此类研究具有挑战性。
