Ultrasound-Based Scaffold-Free Core-Shell Multicellular Tumor Spheroid Formation.

Karl Olofsson,Björn Önfelt,Madoka Takai,Martin Wiklund,Valentina Carannante

doi:10.3390/mi12030329

Abstract

In cancer research and drug screening, multicellular tumor spheroids (MCTSs) are a popular model to bridge the gap between in vitro and in vivo. However, the current techniques to culture mixed co-culture MCTSs do not mimic the structural architecture and cellular spatial distribution in solid tumors. In this study we present an acoustic trapping-based core-shell MCTSs culture method using sequential seeding of the core and shell cells into microwells coated with a protein repellent coating. Scaffold-free core-shell ovarian cancer OVCAR-8 cell line MCTSs were cultured, stained, cleared and confocally imaged on-chip. Image analysis techniques were used to quantify the shell thickness (23.2 ± 1.8 µm) and shell coverage percentage (91.2 ± 2.8%). We also show that the shell thickness was evenly distributed over the MCTS cores with the exception of being slightly thinner close to the microwell bottom. This scaffold-free core-shell MCTSs formation technique and the analysis tools presented herein could be used as an internal migration assay within the MCTS or to form core-shell MCTS co-cultures to study therapy response or the interaction between tumor and stromal cells.

Highlights

The refractive index matching solution (RIMS) clearing strategy allowed for whole multicellular tumor spheroids (MCTSs) confocal imaging (Figure 2a)
We have demonstrated a ultrasonic standing wave (USW)-based technique for parallel formation and culture of a 100 uniformly sized scaffold-free core-shell MCTSs in a multiwell microplate
The shell thickness did not depend on the azimuth angle θ while the shell thickness was lower in the −π/2 to −π/4 polar angle region, which corresponds to the lower parts of the MCTSs

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Solid cancer tumors are cells embedded in a complex tissue architecture allowing cellular communication through direct contact or soluble factors [1,2]. Together with the tumor specific biophysical and biochemical factors permeating the 3D architecture, the tumor microenvironment influences cell behavior and tumor progression [3]. Standard in vitro 2D cultures, where cells are maintained on flat surfaces, do not mimic crucial aspects of the solid tumor and its microenvironment [4]

Methods

Results

Conclusion