Visualization of mechanical forces in 3D cell models with molecular DNA tension probe.

Abstract

Mechanical force can act as an important stimulus to regulate cellular processes. Accurate measurement of these forces plays a fundamental role in our understanding of cell mechanosensing and mechanotransduction. Current methods have focused on investigating the cell-matrix and intercellular forces on 2D monolayer cell models. In contrast, cells in real biological systems exist in multilayers and expose to forces from 3D directions. Exploring cellular mechanical forces in 3D cell models is thus critical to reveal their native interaction patterns in organs or tissues. We have recently developed a type of lipid-DNA-based molecular tension probes that have emerged as a potent tool for imaging intercellular mechanical forces. In this work, we have further investigated the potential usage of these molecular DNA tension probes for measuring mechanical forces in 3D spheroids and organoids. Using tumor spheroids and stem cell organoids of different sizes and shapes, we first characterized and optimized the probe penetration and cell membrane modification kinetics and efficiencies of the lipid-DNA conjugates. Afterwards, as a proof of concept, E-cadherin-mediated intercellular tensile forces were imaged and quantified in these 3D cell models using designer ratiometric DNA tension probes. Such membrane tensile force measurement was enabled because these DNA hairpin-based probes can convert cellular mechanical forces into digital fluorescence signals. These optimized DNA tension probes can also be used to investigate the dynamic changes and spatial distributions of different cellular mechanotransduction processes. We believe this is an important study that can potentially fill the gap between current studies of 2D cell mechanics and that in real 3D biological models.