Barata, D. | bioRxiv Science

bioRxiv2022

Generating fast-twitch myotubes in vitro using an optogenetic-based, quantitative contractility assay

The composition of fiber types within skeletal muscle impacts the tissues physiological characteristics and susceptibility to disease and ageing. In vitro systems should therefore account for fiber type composition when modelling muscle conditions. To induce fiber specification in vitro, we designed a quantitative contractility assay based on optogenetics and particle image velocimetry. We submitted cultured myotubes to long-term intermittent light stimulation patterns and characterized their structural and functional adaptations. After several days of in vitro exercise, myotubes contract faster and are more resistant to fatigue. The enhanced contractile functionality was accompanied by advanced maturation such as increased width and upregulation of neuron receptor genes. We observed an upregulation in the expression of distinct myosin heavy chain isoforms (namely, neonatal-Myh8 and fast-Myh), which induced a shift towards a fast fiber phenotype. This long-term in vitro exercise strategy can be used to study fiber specification and refine muscle disease modelling.

cell biology↗

bioRxiv2021

Competition for endothelial cell polarity drives vascular morphogenesis

Blood vessel formation generates unique vascular patterns in each individual. The principles governing the apparent stochasticity of this process remain to be elucidated. Using mathematical methods, we find that the transition between two fundamental vascular morphogenetic programs - sprouting angiogenesis and vascular remodeling - is established by a shift on collective front-rear polarity of endothelial cells. We demonstrate that the competition between biochemical (VEGFA) and mechanical (blood flow-induced shear stress) cues controls this collective polarity shift. Shear stress increases tension at focal adhesions overriding VEGFA-driven collective polarization, which relies on tension at adherens junctions. We propose that vascular morphogenetic cues compete to regulate individual cell polarity and migration through tension shifts that translates into tissue-level emergent behaviors, ultimately leading to uniquely organized vascular patterns.

developmental biology↗