Structural and Mechanical Characterization of Collagen-Hyaluronan Hydrogels Used to Study Cancer Cell Invasion through the Bladder Wall

Collagen-hyaluronic acid (Col-HA) hydrogels are widely studied as biomimetic materials that recapitulate the environmental physical and mechanical properties crucial for understanding the cell behavior during cancer invasion and progression. Our research focused on Col-HA hydrogels as an environment to study the invasion of bladder cancer cells through the bladder wall. The bladder is a heterogeneous structure composed of three main layers: urothelium (the softest), lamina propria (the stiffest), and the muscle outer layer, with elastic properties lying between the two. Thus, the bladder cancer cells migrate through the mechanically distinct environments. We investigated the impact of Col-HA hydrogel microstructure and rheology on migrating bladder cancer T24 cells from the cancer spheroid surface to the surrounding environment formed from various collagen I and HA concentrations and chemical structures. The designed hydrogels showed variability in network density and rheological properties. The migration of bladder cancer cells was inhibited inside hydrogels of ∼1 kPa storage modulus. The correlation analysis showed that collagen concentration primarily defined the rheological properties of Col-HA hydrogels, but hydrogels can soften or stiffen depending on the type of HA used. Within soft Col-HA hydrogels, cells freely invade the surrounding environment, while its stiffening impedes cell movement and almost inhibits cell migration. Only individual, probably leading, cells are observed at the spheroid edges initiating the invasion. Our findings showed that the rheological properties of the hydrogels dominate in regulating cancer cell migration, providing a platform to study how bladder cancer cells migrate through the heterogeneous structure of the bladder wall.