Live 3D imaging and mapping of shear stresses within tissues using incompressible elastic beads

Abstract

To investigate the role of mechanical constraints in morphogenesis and development, we develop a pipeline of techniques based on incompressible elastic sensors. These techniques combine the advantages of incompressible liquid droplets, which have been used as precise in situ shear stress sensors, and of elastic compressible beads, which are easier to tune and to use. Droplets of a polydimethylsiloxane (PDMS) mix, made fluorescent through specific covalent binding to a rhodamin dye, are produced by a microfluidics device. The elastomer rigidity after polymerization is adjusted to the tissue rigidity. Its mechanical properties are carefully calibrated in situ, for a sensor embedded in a cell aggregate submitted to uniaxial compression. Thelocal shear stress tensor is retrieved from the sensor shape, accurately reconstructed through an active contour method. In vitro, within cell aggregates, and in vivo, in the prechordal plate of the Zebrafish embryo during gastrulation,our pipeline of techniques demonstrates its efficiency to directly measure the three dimensional shear stress repartition within a tissue.

A microfluidic platform to investigate the role of mechanical constraints on tissue reorganization

“…Improvements could include changes in constriction walls, which could be rounded or at angles smaller than 90 degrees. Embedding deformable stress sensors inside the tissue (20,(36)(37)(38) would enable to relate cell deformation with the local tissue stress to validate further rheological models; beyond the linear models we test here, future works might investigate more realistic power-law rheologies. Further progresses could come from improved time and space resolutions, segmentation and tracking, to obtain better statistics; dynamic stress inference (which applies even to moving junctions) (39,40) could infer junctions tensions and determine how they are modulated by cell deformations and rearrangements.…”

A microfluidic platform to investigate the role of mechanical constraints on tissue reorganization

“…In addition, the mechanical stress field is unknown inside aspired tissues: embedding deformable stress sensors inside the tissue (18,(38)(39)(40) would enable to relate cell deformation with the local tissue stress. We could also use cell segmentation to infer junctions tensions (41) and how they are modulated by cell deformations and rearrangements.…”

“…Improvements could include changes in constriction walls, which could be rounded or at angles smaller than 90 degrees. Embedding deformable stress sensors inside the tissue (20, 36–38) would enable to relate cell deformation with the local tissue stress to validate further rheological models; beyond the linear models we test here, future works might investigate more realistic power-law rheologies.…”

Squeezing the eggs to grow: The mechanobiology of mammalian folliculogenesis

“…To evaluate mechanical stress in tissue interior, several techniques have been developed in recent years. For example, hydrogel-based deformable beads have been developed, which allows ones to quantify the local stress fields in living tissues, as demonstrated in zebrafish and in vitro cell aggregates (Dolega et al, 2017;Mohagheghian et al, 2018;Träber et al, 2019;Souchaud et al, 2022). Larger beads have been used to infer the contractile stress exerted by cells.…”