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PhD Discussions Sessions: Jesús Ordoño and Ernest Latorre
Friday, June 1, 2018 @ 10:00 am–11:00 am
Lactate-based strategy for cardiac tissue engineering
Jesús Ordoño, Biomaterials for regenerative therapiesLactate is a metabolite of glycolysis, commonly produced by cells consuming glucose. However, growing evidences suggest new roles for this molecule, as it has shown to act as a signalling molecule in many tissues. In this work, we explore the effects of lactate on cardiac cells for tissue engineering applications. Our results demonstrate that lactate enhance cardiomyocyte proliferation and modulates different cell cycle related proteins, supporting thus the idea that this molecule can be able to reprogram cardiomyocytes towards a more immature stage. Cardiac fibroblasts also show a dose-dependent response to lactate by modifying their secretome, hence promoting a suitable environment for cardiac regeneration. Ex vivo culture of mouse hearts revealed the ability of lactate to increase survival of cardiomyocytes as well as to prolong the beating capacity of the cardiac tissue.
With all these new evidences of the action of lactate, we cultured cardiac cells on a 3D scaffold based on collagen and elastin, allowing engraftment and beating of the cardiac tissue. The response of such system to external electrical stimulus was evaluated using a pulsatile electric field stimulation, showing a proliferative and more immature behaviour of the tissue in the presence of lactate. Cardiac cells also showed expression of specific lactate receptors and transporters, such as MCT1, MCT4 and GPR81. The correct development of sarcomeric structures was confirmed, as well as the coupling and presence of intercalated disks. In conclusion, lactate arises as a novel and feasible option to promote cardiac regeneration, and therefore lactate-releasing scaffolds are a suitable strategy for cardiac tissue regeneration.
Active superelasticity revealed by three-dimensional epithelial sheets of controlled size and shape
Ernest Latorre, Integrative cell and tissue dynamicsFundamental processes in development and physiology are determined by the three-dimensional architecture of epithelial sheets. How these sheets deform and fold into complex structures has remained unclear, however, because their mechanical properties in three-dimensions have not been accessed experimentally. By combining measurements of epithelial tension, shape, and luminal pressure, here we show that epithelial cell sheets are active superelastic materials. We develop a new micropattering approach to produce massive arrays of epithelial domes with controlled basal shape and size. By measuring 3D deformations of the substrate and curvature of the dome we obtain a direct measurement of luminal pressure and epithelial tension. Observations over time-scales of hours allow us to map the epithelial tension-strain response, revealing a tensional plateau over several-fold areal strain reaching 300%. We show that these extreme nominal strains are accommodated by a highly heterogeneous stretching of individual cells, with barely deformed cells coexisting with others reaching 1000% areal strain, in seeming contradiction with the measured tensional uniformity. This phenomenology is reminiscent of superelasticity, a mechanical response generally attributed to microscopic material instabilities in metal alloys. We provide evidence that this instability is triggered in epithelial cells by limited availability of components of the actomyosin cortex. Finally, we implement 3D vertex model, which captures both the tension/strain relationship and strain heterogeneity. Our study unveils a new type of mechanical behavior -active superelasticity- that enables epithelial sheets to sustain extreme stretching under constant tension.
