Liu Zhen, Jian Ziying, Wang Qian, Cheng Tao, Feuerecker Benedikt, Schwaiger Markus, Huang Sung-Cheng, Ziegler Sibylle I, Shi Kuangyu
Department of Nuclear Medicine, Technische Universität München, Munich, Germany; and
Department of Nuclear Medicine, Technische Universität München, Munich, Germany; and.
J Nucl Med. 2016 Oct;57(10):1548-1555. doi: 10.2967/jnumed.115.169151. Epub 2016 Jun 30.
Measurement of cellular tracer uptake is widely applied to learn the physiologic status of cells and their interactions with imaging agents and pharmaceuticals. In-culture measurements have the advantage of less stress to cells. However, the tracer solution still needs to be loaded, unloaded, and purged from the cell culture during the measurements. Here, we propose a continuously infused microfluidic radioassay (CIMR) system for continuous in-culture measurement of cellular uptake. The system was tested to investigate the influence of the glucose concentration in cell culture media on F-FDG uptake kinetics.
The CIMR system consists of a microfluidic chip integrated with a flow-control unit and a positron camera. Medium diluted with radioactive tracer flows through a cell chamber continuously at low speed. Positrons emitted from the cells and from tracer in the medium are measured with the positron camera. The human cell lines SkBr3 and Capan-1 were incubated with media of 3 different glucose concentrations and then measured with F-FDG on the CIMR system. In addition, a conventional uptake experiment was performed. The relative uptake ratios between different medium conditions were compared. A cellular 2-compartment model was applied to estimate the cellular pharmacokinetics on CIMR data. The estimated pharmacokinetic parameters were compared with expressions of glucose transporter-1 (GLUT1) and hexokinase-2 measured by quantitative real-time polymerase chain reaction.
The relative uptake ratios obtained from CIMR measurements correlated significantly with those from the conventional uptake experiments. The relative SDs of the relative uptake ratios obtained from the CIMR uptake experiments were significantly lower than those from the conventional uptake experiments. The fit of the cellular 2-compartment model to the F-FDG CIMR measurements was of high quality. For SkBr3, the estimated pharmacokinetic parameters k and k were consistent with the messenger RNA expression of GLUT1 and hexokinase-2: culturing with low glucose concentrations led to higher GLUT1 and hexokinase-2 expression as well as higher estimated k and k For Capan-1, the estimated k and k increased as the glucose concentration in the culture medium decreased, and this finding did not match the corresponding messenger RNA expression.
The CIMR system captures dynamic uptake within the cell culture and enables estimation of the cellular pharmacokinetics.
细胞示踪剂摄取的测量被广泛应用于了解细胞的生理状态及其与成像剂和药物的相互作用。培养内测量对细胞的压力较小。然而，在测量过程中，示踪剂溶液仍需要加载、卸载并从细胞培养物中清除。在此，我们提出一种连续输注微流体放射分析（CIMR）系统，用于在培养过程中连续测量细胞摄取。该系统经过测试，以研究细胞培养基中葡萄糖浓度对F-FDG摄取动力学的影响。
CIMR系统由一个与流量控制单元和正电子相机集成的微流体芯片组成。用放射性示踪剂稀释的培养基以低速连续流过细胞室。用正电子相机测量细胞和培养基中示踪剂发射的正电子。将人细胞系SkBr3和Capan-1与3种不同葡萄糖浓度的培养基孵育，然后在CIMR系统上用F-FDG进行测量。此外，进行了传统的摄取实验。比较了不同培养基条件下的相对摄取率。应用细胞双室模型来估计CIMR数据上的细胞药代动力学。将估计的药代动力学参数与通过定量实时聚合酶链反应测量的葡萄糖转运蛋白-1（GLUT1）和己糖激酶-2的表达进行比较。
CIMR测量获得的相对摄取率与传统摄取实验获得的相对摄取率显著相关。CIMR摄取实验获得的相对摄取率的相对标准差显著低于传统摄取实验。细胞双室模型对F-FDG CIMR测量的拟合质量很高。对于SkBr3，估计的药代动力学参数k和k与GLUT1和己糖激酶-2的信使RNA表达一致：在低葡萄糖浓度下培养导致更高的GLUT1和己糖激酶-2表达以及更高的估计k和k。对于Capan-1，估计的k和k随着培养基中葡萄糖浓度的降低而增加，这一发现与相应的信使RNA表达不匹配。
CIMR系统可捕捉细胞培养内的动态摄取，并能够估计细胞药代动力学。
