Development of angiogenesis assays using 3D-cell spheres

Abstract

3-dimensional (3D) cell culture systems are superior over conventional 2D-systems as they more naturally model the in vivo situation in terms of cell-cell and cell- matrix interactions. 3D-models are therefore preferable for in vitro drug screening and the analysis of biological processes that are relevant e.g. for tumor angiogenesis. A disadvantage of 3D-systems is the lack of standardized high throughput and high content screening (HCS) technologies. The most established in vitro 3D system is the cultivation of the cells in suspension in order to promote the establishment of spheres. Here, we aimed to investigate whether a cell-sphere based pipeline for the analysis of neoangiogenesis by HCS technology can be developed. HCS is an optical method allowing high-throughput analysis of cells. We established spheres from neurofibrosarcoma, mesenchymal and human induced pluripotent stem cells (embryoid bodies, EB) for the analysis of the tumor-driven induction of endothelial markers in the stem cell spheres as a model for neoangiogenesis. To this end tumor spheres and stem cell spheres were contact-co-cultured. This model was then tested for applicability in HCS and it was shown that the early endothelial marker vascular endothelial growth factor receptor 2 (VEGFR2) is induced by tumor spheres in EBs. Furthermore, to enable reproducible HCS of sphere co-cultures, a matrix-printing method for selective and spatially controlled attachment of spheres was established and tested. In conclusion, the work (i) established a sphere-based 3D technology to analyze angiogenic induction by tumor cells and (ii) developed a matrix printed array that facilitates arrangement of spheres and controlling of confrontation cultures for high content screening.