A Minimalistic in Vitro 3D Model to Study F98 Rat Brain Tumor Growth

Classical in vitro methods for studying cell behavior, mainly 2D cell cultures on Petri dishes, suffer from many biases (simple dimensionality, absence of biochemical gradients, rigidity⋯). On the other hand, in vivo studies involve very complex systems and do not allow separating the role of each component. Alternative strategies inspired from in vivo tissue's architecture and composition, have been under development for years, in order to mimic extracellular 3D matrix (ECM). Among them, synthetic hydrogels are good in vitro minimalistic models, allowing fine tuning of their composition as well as their structural and functional features.In this context, we manufactured an original PEG-based hydrogel grafted with poly-L-lysine moieties in order to: i) validate this substrate as an artificial 3D ECM; ii) follow the growth (proliferation, migration) of a population of the F98 rat glioma cell line in this minimalistic tissue-like structure.First, we studied the hydrogel physical properties when varying the size and concentration of PEG and poly-L-lysine, using rheology and FRAP. In particular, we explored a range of rigidities, including that of brain ECM (1kPa), and diffusivities following different polymer mesh size. In a second step, we examined how the gel properties and its composition (PEG and poly-L-lysine) influence the organization and growth rate of the cell population.In our 3D substrate, cells have rounded shape different from 2D form. They organize as aggregates for which growth rate and shape varies as a function of hydrogel composition: the higher is the density of PEG and poly-L-lysine, the smaller is the size of the aggregates.Finally, our data clearly give an insight on how spatial constraints in the 3D hydrogel architecture limit tumor's progression into the polymer network. Correlation with in vivo characteristics would be further investigated.