Study on the Expansion Dynamics of MDCK Epithelium by Interstitial Flow Using a Traction Force-Measurable Microfluidic Chip.

Mirim Kim,Yongdoo Park,Hwanseok Jang

doi:10.3390/ma14040935

Abstract

The movement of collective cells is affected through changes in physical interactions of cells in response to external mechanical stimuli, including fluid flow. Most tissues are affected by fluid flow at the interstitial level, but few studies have investigated the physical effects in collective cells affected by a low flow rate. In this study, collective cell migration of Madin–Darby canine kidney (MDCK) epithelial cells was investigated under static or interstitial flow (0, 0.1, and 1 μL/min) using a traction microfluidic device. The optimization of calculation of cellular traction forces was first achieved by changing interrogation window size from the fluorescent bead images. Migration analysis of cell collectives patterned with a 700 μm circular shape reveals that cells under the slow flow (0.1 and 1 μL/min) showed the inhibitory migration by decreasing cell island size and cellular speed compared to that of static condition. Analysis of cellular forces shows that level of traction forces was lower in the slow flow condition (~20 Pa) compared to that of static condition (~50 Pa). Interestingly, the standard deviation of traction force of cells was dramatically decreased as the flow rate increased from 0 to 1 μL/min, which indicates that flow affects the distribution of cellular traction forces among cell collectives. Cellular tension was increased by 50% in the cells under the fluid flow rate of 1 μL/min. Treatment of calcium blocker increased the migratory speed of cells under the flow condition, whereas there is little change of cellular forces. In conclusion, it has been shown that the interstitial flow inhibited the collective movement of epithelial cells by decreasing and re-distributing cellular forces. These findings provide insights into the study of the effect of interstitial flow on cellular behavior, such as development, regeneration, and morphogenesis.

Highlights

The collective migration of cells is a form of harmonized behavior required for critical life activities such as development [1,2] and regeneration [3] as well as for cancer metastasis [4]
To analyze the effect of fluid flow on collective cellular movement from a physical perspective, we used a combination of microfluidic chip and traction force microscopy (Figure 1)
In measuring the bead displacement, IW 32 detected the ment of particles is calculated by assessing the cross-correlation of a widest range of displacement but still showed excessively concentrated values near 0 in specified interrogation window (IW) size

Summary

Introduction

The collective migration of cells is a form of harmonized behavior required for critical life activities such as development [1,2] and regeneration [3] as well as for cancer metastasis [4]. Tissues and organs consist of physically connected cells that move by exerting mechanical forces in response to their extracellular environment, which includes mechanical stimuli [3,5,6]. One type of mechanical stimulus is fluid flow that modulates the functions of cells and organs in the body. For higher flow rates, such as in the aorta and vena cava, ranging around 20 dyn/cm2 [7], studies are focused on the endothelial cells showing changes in morphological and physiological aspects, such as alignment of cytoskeletal structure [8,9] and the induction of genes related to shear stress [10]. For lower flow rates, such as capillary flow [11], studies are focused on the integrity of the endothelial cell monolayer related to controlling permeability [12]. Low flow rates exist in the epithelium when building tissue lumen or ducts

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Results

Conclusion