Nanobiosensorics Laboratory, Institute of Technical Physics and Materials Science, Centre for Energy Research, Budapest, Hungary.
Department of Electronics Technology, Faculty of Electrical Engineering and Informatics, Budapest University of Technology and Economics, Budapest, Hungary.
Sci Rep. 2022 May 11;12(1):7747. doi: 10.1038/s41598-022-11770-z.
Single-cell adhesion plays an essential role in biological and biomedical sciences, but its precise measurement for a large number of cells is still a challenging task. At present, typical force measuring techniques usually offer low throughput, a few cells per day, and therefore are unable to uncover phenomena emerging at the population level. In this work, robotic fluidic force microscopy (FluidFM) was utilized to measure the adhesion parameters of cells in a high-throughput manner to study their population distributions in-depth. The investigated cell type was the genetically engineered HeLa Fucci construct with cell cycle-dependent expression of fluorescent proteins. This feature, combined with the high-throughput measurement made it possible for the first time to characterize the single-cell adhesion distributions at various stages of the cell cycle. It was found that parameters such as single-cell adhesion force and energy follow a lognormal population distribution. Therefore, conclusions based on adhesion data of a low number of cells or treating the population as normally distributed can be misleading. Moreover, we found that the cell area was significantly the smallest, and the area normalized maximal adhesion force was significantly the largest for the colorless cells (the mitotic (M) and early G1 phases). Notably, the parameter characterizing the elongation of the cells until the maximum level of force between the cell and its substratum was also dependent on the cell cycle, which quantity was the smallest for the colorless cells. A novel parameter, named the spring coefficient of the cell, was introduced as the fraction of maximal adhesion force and maximal cell elongation during the mechanical detachment, which was found to be significantly the largest for the colorless cells. Cells in the M phase adhere in atypical way, with so-called reticular adhesions, which are different from canonical focal adhesions. We first revealed that reticular adhesion can exert a higher force per unit area than canonical focal adhesions, and cells in this phase are significantly stiffer. The possible biological consequences of these findings were also discussed, together with the practical relevance of the observed population-level adhesion phenomena.
单细胞黏附在生物和生物医学科学中起着至关重要的作用，但对大量细胞进行精确测量仍然是一项具有挑战性的任务。目前，典型的力测量技术通常提供低通量，每天只有几个细胞，因此无法揭示在群体水平上出现的现象。在这项工作中，我们利用机器人流体力学显微镜（FluidFM）以高通量的方式测量细胞的黏附参数，深入研究它们的群体分布。所研究的细胞类型是具有荧光蛋白细胞周期依赖性表达的基因工程 HeLa Fucci 构建体。这一特征，再加上高通量测量，使得首次有可能对细胞周期各阶段的单细胞黏附分布进行特征描述。结果发现，单细胞黏附力和能量等参数呈对数正态分布。因此，基于少量细胞的黏附数据得出的结论或假设群体呈正态分布可能会产生误导。此外，我们发现无色细胞（有丝分裂（M）和早期 G1 期）的细胞面积最小，归一化的最大黏附力最大。值得注意的是，细胞在达到与基质之间的最大力水平之前的伸长参数也依赖于细胞周期，无色细胞的这个参数最小。引入了一个新的参数，称为细胞的弹簧系数，它是在机械分离过程中最大黏附力和最大细胞伸长的分数，无色细胞的这个参数最大。M 期的细胞以非典型的方式黏附，形成所谓的网状黏附，与典型的黏附斑不同。我们首次揭示了网状黏附可以比典型的黏附斑施加更高的单位面积力，并且这个阶段的细胞明显更硬。还讨论了这些发现的可能生物学后果，以及观察到的群体水平黏附现象的实际意义。
