Oxygen tension modulates cell function in an in vitro three-dimensional glioblastoma tumor model

Hypoxia is a typical feature of the tumor microenvironment, one of the most critical factors affecting cell behavior and tumor progression. However, the lack of tumor models able to precisely emulate natural brain tumor tissue has impeded the study of the effects of hypoxia on the progression and growth of tumor cells. This study reports a three-dimensional (3D) brain tumor model obtained by encapsulating U87MG (U87) cells in a hydrogel containing type I collagen. It also documents the effect of various oxygen concentrations (1%, 7%, and 21%) in the culture environment on U87 cell morphology, proliferation, viability, cell cycle, apoptosis rate, and migration. Finally, it compares two-dimensional (2D) and 3D cultures. For comparison purposes, cells cultured in flat culture dishes were used as the control (2D model). Cells cultured in the 3D model proliferated more slowly but had a higher apoptosis rate and proportion of cells in the resting phase (G0 phase)/gap I phase (G1 phase) than those cultured in the 2D model. Besides, the two models yielded significantly different cell morphologies. Finally, hypoxia (e.g., 1% O₂) affected cell morphology, slowed cell growth, reduced cell viability, and increased the apoptosis rate in the 3D model. These results indicate that the constructed 3D model is effective for investigating the effects of biological and chemical factors on cell morphology and function, and can be more representative of the tumor microenvironment than 2D culture systems. The developed 3D glioblastoma tumor model is equally applicable to other studies in pharmacology and pathology.