(571e) Stimulation of Glioma Cell Malignancy Under Defined Microenvironmental Conditions

Pedron, S. - Presenter, University of Illinois at Urbana-Champaign
Becka, E., Institute for Genomic Biology
Harley, B. A. C., University of Illinois at Urbana-Champaign

Malignant glioma cells are especially motile and can migrate diffusely through the brain parenchyma, leading to very inefficient therapies. This aggressiveness and treatment failure is likely related to tumor heterogeneity, and how glioma cells interpret the complex 3D matrix microenvironment is not well understood. We use a microfluidic device in which stable gradients are established and resulting materials can be directly analyzed. We aim to identify the matrix characteristics that can impact glioma phenotype similarly to the native tissue.

The design of the microfluidic diffusive mixer contains channels with a 200 µm (wide) x 100 µm (tall) cross-section with 50 µm high staggered herringbone features. Hydrogels were prepared by UV cross-linking of a monomer solution (methacrylated HA / methacrylated gelatin) with a photoinitiator in the presence of U87MG tumor cells. GelMA was synthesized using various concentrations of methacrylic anhydride to create polymers with different degrees of methacrylation. The gene expression levels were measured using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Protein secreted by encapsulated cells was quantified by ELISA.

Spatial and temporal gradients regulate the cell proliferation, migration, and differentiation during cancer. Therefore, we use a microfluidic approach to fabricate patterned biomaterials that have the ability to examine transitions between defined environments. We developed a series of gelatin and hyaluronic acid (HA) macromers in order to create libraries of composite hydrogel structures. Biophysical properties were tuned by altering gel crosslinking densities and composition. These materials allowed us to investigate the influence of cell-matrix interactions on metrics of malignancy using the U87MG human GBM cell line, notably cell morphology, gene expression (e.g., MMPs, VEGF, Fn and HIF-1) profiles and protein secretion in response to local mechanical, structural, and diffusivities of the GelMA matrix. Hydrogels containing hyaluronic acid (HA) show significant impact on GBM malignancy metrics in comparison to 2D culture or through the use of 3D GelMA hydrogels. Glioma cell clusters were observed exclusively in HA containing gels as well as HA-dose dependent gene expression patterns. Biochemical cues also stimulated malignancy of glioma cells over-expressing the epithelial growth factor receptor (EGFR), a mutation that affects a large percentage of glioblastomas.

Gelatin and HA patterned hydrogel systems offer well-defined and reproducible extracellular microenvironments for studying cancer development. Gradient systems are proven to be faster and more biologically relevant than 2D or discrete scaffold systems and can be used to identify more specific and effective therapies as well as design diagnostic platforms.