Experimental and modeling study of the formation of cell aggregates with differential substrate adhesion

Abstract

The study of cell aggregation in vitro has a tremendous importance these days. In cancer biology, aggregates and spheroids serve as model systems and are considered as pseudotumors that are more realistic than 2D cell cultures. Recently, in the context of brain tumors (gliomas), we developed a new poly(ethylene glycol) (PEG)-based hydrogel, with adhesive properties that can be controlled by the addition of poly(L-lysine) (PLL), and a stiffness close to the brain's. This substrate allows the motion of individual cells and the formation of cell aggregates (within one day), and we showed that on a non-adhesive substrate (PEG without PLL is inert for cells), the aggregates are bigger and less numerous than on an adhesive substrate (with PLL). In this article, we present new experimental results on the follow-up of the formation of aggregates on our hydrogels, from the early stages (individual cells) to the late stages (aggregate compaction), in order to compare, for two cell lines (F98 and U87), the aggregation process on the adhesive and non-adhesive substrates. We first show that a spaceless model of perikinetic aggregation can reproduce the experimental evolution of the number of aggregates, but not of the mean area of the aggregates. We thus develop a minimal off-lattice agent-based model, with a few simple rules reproducing the main processes that are at stack during aggregation. Our spatial model can reproduce very well the experimental temporal evolution of both the number of aggregates and their mean area, on adhesive and non-adhesive soft gels and for the two different cell lines. From the fit of the experimental data, we were able to infer the quantitative values of the speed of motion of each cell line, its rate of proliferation in aggregates and its ability to organize in 3D. We also found qualitative differences between the two cell lines regarding the ability of aggregates to compact. These parameters could be inferred for any cell line, and correlated with clinical properties such as aggressiveness and invasiveness.

Collective directional migration drives the formation of heteroclonal cancer cell clusters

“…Overall, this phenomenon occurs on a timescale of the order of a week for all cell lines considered. This is consistent with what previously measured for PC-3 cells [32], and is also significantly different from what observed in liquid overlay cultures, where random movement is predominant [58-60], and the dynamics is much faster, with aggregation times estimated as less than a day.…”

Collective directional migration drives the formation of heteroclonal cancer cell clusters

“…Overall, this phenomenon occurs on a timescale of the order of a week for all cell lines considered. This is consistent with what was previously measured for PC-3 cells [32], and is also significantly different from what was observed in liquid overlay cultures, where random movement is predominant [68][69][70] and the dynamics are much faster, with aggregation times estimated as less than a day.…”

A Reverse Transfection System with Cationized Gelatin Nanospheres Incorporating Molecular Beacon as a Tool to Visualize Cell Function

“…3D cell aggregates have been widely used as a tool to mimic the in vivo environment. ,− However, due to the lack of oxygen and nutrition, the cells located in the center of aggregates tend to die. To break through this problem, GMS are effective in functioning as a cell scaffold, which allows cells to supply oxygen and nutrition. ,− On the other hand, GMS are a good carrier for biomolecules, such as low molecular-weight drug, protein, and siRNA, to achieve the controlled release. − Increasing biological functions in cell aggregates would be achieved by preparing cell aggregate with biomolecules loaded GMS.…”