Modeling and measuring intracellular displacement during cell penetration

Abstract

Cell penetration is a typical micromanipulation technique widely utilized in many cell biological applications. The significant cell deformation generated during penetration can mechanically damage the cell and even cause the death of the cell. Measuring the intracellular displacement resulting from cell deformation can provide a quantitative evaluation of the mechanical harm done to cells during penetration. The existing labeled intracellular displacement measurement approaches have limitations in spatial resolution and must introduce markers, which cause further harm to the cell. Moreover, label-free methods, such as traditional optical flow methods, are not suitable for measuring the inconsistent intracellular displacement distribution due to cell penetration. This paper presents a label-free noncontact method for measuring the intracellular displacements during penetration. First, based on a finite element simulation, the uneven distribution of intracellular displacements due to penetration was modeled by a quadratic model. Then, by combining the obtained displacement model with the Farnebäck dense optical flow method, a model-based optical flow method was developed to measure intracellular displacements. Finally, the method was used to ascertain the intracellular displacement in porcine oocyte penetration experiments. The forward-backward error of the proposed detection method is less than 0.5 pixels, lower by 49.3% and 26.1%, respectively, compared with two typical Farnebäck optical flow methods. This method could be used to analyze cell damage during penetration. With an appropriate extension, the method may be suitable for measuring the intracellular displacement due to cell manipulations other than penetration.