Heat shock treatment increases cell viability after bioprinting

Abstract text (incl. figure legends and references)

Introduction

Bioprinting is a valuable tool to create tunable biomimetic systems, however stress introduced by the printing process can change cell structure. Heat shock response is a conserved cellular reaction to various environmental stressors resulting in the expression of heat shock proteins which prevent or reverse protein misfolding.

Objectives

Using heat shock (HS) treatment prior to bioprinting we aim to stabilize the cell cytoskeleton to increase cell survival during the bioprinting process.

Materials and Methods

Endothelial cells were harvested, encapsulated in hydrogels, then printed using a drop-on-demand bioprinter or casted by hand. Metabolism via ATP was measured using a luminescent assay. Morphology and protein levels were analyzed using brightfield and IF with confocal fluorescent microscopy. Expression levels were analyzed using RNAseq.

Results

A significant reduction in viability is seen in the untreated printed cells but not in in printed HS treated cells. Metabolic levels are higher in printed cells after HS compared to printed cells with no treatment. Together this indicates HS provides a protective effect. Printed cells show less organized actin filaments with and without HS compared to the untreated control. Protein levels related to cell adhesion also vary between printed and control samples +/- HS as indicated by IF and quantitative image analysis.

Conclusions

The effects of the shear stress during the printing process cause damage to the cytoskeleton and a reduction of cell adhesion factors. Heat shock treatment increases cell viability immediately post printing. Pre-treating cells using HS could be an easy way to increase cell viability in bioprinted constructs.