Tunable Mesoscopic Collagen Island Architectures Modulate Stem Cell Behavior.

The extracellular matrix is the biophysical environment that scaffolds mammalian cells in the body. The main constituent is collagen. In physiological tissues, collagen network topology is diverse with complex mesoscopic features. While studies have explored the roles of collagen density and stiffness, the impact of complex architectures remains not well-understood. Developing in vitro systems that recapitulate these diverse collagen architectures is critical for understanding physiologically relevant cell behaviors. Here, methods are developed to induce the formation of heterogeneous mesoscopic architectures, referred to as collagen islands, in collagen hydrogels. These island-containing gels have highly tunable inclusions and mechanical properties. Although these gels are globally soft, there is regional enrichment in the collagen concentration at the cell-scale. Collagen-island architectures are utilized to study mesenchymal stem cell behavior, and it is demonstrated that cell migration and osteogenic differentiation are altered. Finally, induced pluripotent stem cells are cultured in island-containing gels, and it is shown that the architecture is sufficient to induce mesodermal differentiation. Overall, this work highlights complex mesoscopic tissue architectures as bioactive cues in regulating cell behavior and presents a novel collagen-based hydrogel that captures these features for tissue engineering applications.

Cytoskeletal dynamics regulates stromal invasion behavior of distinct liver cancer subtypes.

Drug treatment against liver cancer has limited efficacy due to heterogeneous response among liver cancer subtypes. In addition, the functional biophysical phenotypes which arise from this heterogeneity and contribute to aggressive invasive behavior remain poorly understood. This study interrogated how heterogeneity in liver cancer subtypes contributes to differences in invasive phenotypes and drug response. Utilizing histological analysis, quantitative 2D invasion metrics, reconstituted 3D hydrogels, and bioinformatics, our study linked cytoskeletal dynamics to differential invasion profiles and drug resistance in liver cancer subtypes. We investigated cytoskeletal regulation in 2D and 3D culture environments using two liver cancer cell lines, SNU-475 and HepG2, chosen for their distinct cytoskeletal features and invasion profiles. For SNU-475 cells, a model for aggressive liver cancer, many cytoskeletal inhibitors abrogated 2D migration but only some suppressed 3D migration. For HepG2 cells, cytoskeletal inhibition did not significantly affect 3D migration but did affect proliferative capabilities and spheroid core growth. This study highlights cytoskeleton driven phenotypic variation, their consequences and coexistence within the same tumor, as well as efficacy of targeting biophysical phenotypes that may be masked in traditional screens against tumor growth.