Speaker
Description
Introduction
Cells in vivo encounter geometrically complex microenvironments where curvature at the cellular scale can regulate cell morphology and migration [1]. Reduced ECM curvature near solid tumors, for instance, correlates with increased metastatic rate [2]. These observations have motivated the concept of curvotaxis, describing changes in cell movement due to the curvature cues [3, 4]. However, studies often impose spatially varying and complex structures, making it difficult to delineate effects specifically to curvature. Here, we isolate curvature as a single geometric parameter by confining individual mesenchymal stem cells (MSCs) within C-shaped microgrooves of defined radius and width, enabling a direct investigation of curvotaxis.
Methods
Micromolded agarose walls [5] were fabricated on fibronectin-coated coverslips to confine single MSCs within C-shaped microgrooves. The arc patterns were 10 μm wide with inner radii of 15 or 20 μm and a 270° span. Area-matched rectangular patterns of the same width served as controls. For live imaging, nuclei were labeled with SPY-DNA (Spirochrome) or LaminA–mEmerald. Time-lapse images were acquired every 5 min for 12 hours in a stage-top incubator. Nuclear position and morphology were tracked over time.
Results
Cells conformed to the pattern with asymmetrical nuclear profile biased toward the concave edge, potentially formed by the stress fibers above the nucleus (Fig.A). Nuclear tracking found higher curvature increased cell migration speed and nuclear shape changes and these two metrices were strongly correlated. Interestingly, temporal analysis revealed a time-dependent acceleration of nuclear translocation in the curved patterns, which was not found in the area-matched rectangular patterns.
Discussion
We found cell migration speed to increase with curvature, which strongly correlated with nuclear shape changes. Interestingly, this curvature dependence diminished with time, potentially reflecting early spreading and adaptation to confinement. In contrast, cells in rectangular controls shows no time-dependent trend, supporting a specific role for curvature in cell morphology and motility control. Liu et al. reported an opposite relationship between migration speed and curvature [6], although at larger radius than those tested here (50–100 μm vs 15–20 μm in this study). This discrepancy may arise from differences in cell type and substrate stiffness. We are currently investigating a larger range of curvatures, as well as characterizing the temporal changes in actin and nuclear dynamics to further understand how curvature regulates cell migration.
Reference
Assoian, R.K., et al., Cellular sensing of micron-scale curvature: a frontier in understanding the microenvironment. Open Biol, 2019. 9(10): p. 190155.
2. Fischer, R.S., et al., Contractility, focal adhesion orientation, and stress fiber orientation drive cancer cell polarity and migration along wavy ECM substrates. Proceedings of the National Academy of Sciences, 2021. 118(22): p. e2021135118.
3. Callens, S.J.P., et al., Substrate curvature as a cue to guide spatiotemporal cell and tissue organization. Biomaterials, 2020. 232: p. 119739.
4. Pieuchot, L., et al., Curvotaxis directs cell migration through cell-scale curvature landscapes. Nat Commun, 2018. 9(1): p. 3995.
5. Joo, S., J. Lim, and Y. Nam, Design and Fabrication of Miniaturized Neuronal Circuits on Microelectrode Arrays Using Agarose Hydrogel Micro-molding Technique. BioChip Journal, 2018. 12(3): p. 193-201.
6. Liu, Y., et al., Influence of Curvature on Cell Motility and Morphology during Cancer Migration in Confined Microchannels. ACS Appl Mater Interfaces, 2024. 16(8): p. 9956-9967.
