Panel A shows a schematic of a Polydimethylsiloxane stretching device with vacuum, ring, and post components, plus a top view of a cell positioned on the membrane. Panel B shows a schematic timeline of cells seeded on Fibronectin coated Polydimethylsiloxane, treated with Cycloheximide and HEPES, followed by cargo accumulation at the Trans Golgi Network, application of 0 percent or 15 percent strain, addition of pre-warmed medium, and fixation under stretch at 37 degrees Celsius. Panel C shows fluorescence images of PAUF monomeric Red Fluorescent Protein in Control and 15 percent stretch cells, with cell boundaries outlined. Panel D shows a superplot of the number of CARTS per cell, with the x-axis labeled Control and 15 percent stretch and the y-axis labeled Number of CARTS per cell. Panel E shows a superplot of cell adhesion area (square micrometers), with the x-axis labeled Control and 15 percent stretch and the y-axis labeled Cell adhesion area (square micrometers). Panel F shows a superplot of the number of CARTS per cell adhesion area (square micrometers), with the x-axis labeled Control and 15 percent stretch and the y-axis labeled Number of CARTS per cell adhesion area (square micrometers).
Mechanical strain application on cells increases their secretory capabilities. (A) Schematics of the stretch system used to apply a mechanical strain on cells. (B) Schematic representation of the pipeline followed in the stretching experiments. (C) Representative widefield images of fixed HeLa cells transfected with PAUF-RFP, seeded over FN-coated PDMS membranes, and subjected to no external forces or 15% equibiaxial stretch for 30 min. Cell contours are indicated by dashed white curves. Scale bar, 10 µm. (D–F) SuperPlots showing the indicated cell measurements (small, light-colored symbols; N > 45 per biological replicate) and the mean value for each independent biological replicate (larger, black-outlined circles; n = 3). Each color represents a different experimental replicate. Two-sided parametric ratio paired t test was used. The P values are indicated in the plot.