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PhD Discussions: Thomas Wilson and Judith Fuentes
Friday, October 20 @ 10:00 am–11:30 am
Multiscale buckling of epithelial shells
Thomas Wilson, Integrative Cell and Tissue Dynamics group
Numerous natural and engineered structures are shaped as thin curved shells. When subjected to excessive compressive loading, these shells undergo buckling instabilities that result in wrinkling patterns with complex dynamics. Epithelial tissues such as those enclosing embryos or lining glandular organs are a class of thin shells that displays three distinctive mechanical features: they are viscoelastic over the time scales of physiological loading, they carry an active surface tension, and their stress-bearing elements are distributed across scales. The conditions under which these material properties enable buckling, and the subsequent structural changes are not understood. Here we establish the buckling dynamics of epithelial shells of controlled geometry over several orders of magnitude in time and space. We developed an experimental system that allows us to sculpt epithelial shells and subject them to controlled pressure differentials. We show that, under rapid pressure reductions relative to a characteristic viscoelastic time of the system, the tissue develops buckling patterns with different degrees of symmetry that depend on its size and shape. By contrast, slow deflations allow the tissues to accommodate large strain variations without buckling. Strikingly, we find that epithelial buckling is a multiscale phenomenon involving supracellular folds but also subcellular wrinkles in the actin cortex. Additionally, we can harness the active viscoelastic behaviour of the cell cortex to pattern epithelial folds by rationally directed buckling. Our study shows that epithelial tissues can be understood as hierarchical materials with mechanical instabilities that can be harnessed to engineer morphogenetic events.
Evaluation of self-healing properties in skeletal muscle-based bioactuators
Judith Fuentes, Smart Nano-Bio-Devices group
Three dimensional bioprinting has opened new possibilities for the bioengineering of skeletal muscle models with organization and functionality similar to native tissues. This is key to understand the physiological conditions of skeletal muscle to integrate some of their unique properties, such as self-healing, adaptability, and response to external stimuli, in biohybrid systems. However, the inherent self-healing capability of skeletal muscle has not been fully exploited in these advanced biohybrid platforms. In vivo, skeletal muscle tissue may be repaired via the regenerative function of satellite cells (SC). However, in in vitro conditions, these cells are difficult to expand without altering their self-healing potential. Myogenic reserve cells (RC) offer an alternative potentially useful source to implement advanced regenerative capabilities in biohybrid systems. RC present similar properties to SC and arise during in vitro myoblast differentiation when a subpopulation escape from terminal differentiation. This work presents a 3D-bioprinted skeletal muscle bioactuator which self-healing properties have been evaluated after generating physical damage to the tissue, either by creating cuts or crush injuries. Further studying over the underlying biological events related to muscle repair will be key to moving forward with the design of muscle-based bioactuators with on-demand assisted self-healing properties.