Shirure Venktesh S, Lam Sandra F, Shergill Bhupinder, Chu Yunli E, Ng Natalie R, George Steven C
Department of Biomedical Engineering, University of California Davis, CA, USA.
Department of Biomedical Engineering, Washington University in St. Louis, MO, USA.
Lab Chip. 2020 Aug 11;20(16):3036-3050. doi: 10.1039/d0lc00350f.
Hypoxia, or low oxygen (O2) tension, is a central feature of important disease processes including wound healing and cancer. Subtle temporal and spatial variations (≤1% change) in the concentration of O2 can profoundly impact gene expression and cellular functions. Sodium sulfite reacts rapidly with O2 and can be used to lower the O2 concentrations in PDMS-based tissue culture systems without exposing the cell culture to the chemical reaction. By carefully considering the mass transfer and reaction kinetics of sodium sulfite and O2, we developed a flexible theoretical framework to design an experimental microfluidic system that provides fine spatial and temporal control of O2 tension. The framework packages the dimensions, fluid flow, reaction rates, concentrations, and material properties of the fluidic lines and device into dimensionless groups that facilitate scaling and design. We validated the theoretical results by experimentally measuring O2 tension throughout the experimental system using phosphorescence lifetime imaging. We then tested the system by examining the impact of hypoxia inducible factor-1α (HIF-1α) on the proliferation and migration of MDA-MB-231 breast cancer cells. Using this system, we demonstrate that mild constant hypoxia (≤4%) induces HIF-1α mediated functional changes in the tumor cells. Furthermore, slow (>12 hours), but not rapid (<1 hour), fluctuations in O2 tension impact HIF-1α mediated proliferation and migration. Our results provide a generalized framework for fine temporal and spatial control of O2 and emphasize the need to consider mild spatial and temporal changes in O2 tension as potentially important factors in disease processes such as cancer.
缺氧，即低氧（O2）张力，是包括伤口愈合和癌症在内的重要疾病过程的核心特征。O2浓度的细微时空变化（≤1%变化）会深刻影响基因表达和细胞功能。亚硫酸钠能与O2快速反应，可用于降低基于聚二甲基硅氧烷（PDMS）的组织培养系统中的O2浓度，而不会使细胞培养物暴露于化学反应中。通过仔细考虑亚硫酸钠和O2的传质和反应动力学，我们开发了一个灵活的理论框架，以设计一个能对O2张力进行精细时空控制的实验性微流控系统。该框架将流体管道和装置的尺寸、流体流动、反应速率、浓度及材料特性打包成无量纲组，便于缩放和设计。我们通过使用磷光寿命成像实验测量整个实验系统中的O2张力，验证了理论结果。然后，我们通过研究缺氧诱导因子-1α（HIF-1α）对MDA-MB-231乳腺癌细胞增殖和迁移的影响来测试该系统。使用这个系统，我们证明轻度持续缺氧（≤4%）会诱导肿瘤细胞中HIF-1α介导的功能变化。此外，O2张力缓慢（>12小时）而非快速（<1小时）的波动会影响HIF-1α介导的增殖和迁移。我们的结果为O2的精细时空控制提供了一个通用框架，并强调需要将O2张力的轻度时空变化视为癌症等疾病过程中潜在的重要因素。
