Biology subjects

Smit, T. H.

Publications and source records attributed to Smit, T. H..

3 recordsLinked to original sources

bioRxiv2020

In vivo characterization of chick embryo mesoderm by optical coherence tomography assisted microindentation

Embryos are growing organisms with highly heterogeneous properties in space and time. Understanding the mechanical properties is a crucial prerequisite for the investigation of morphogenesis. During the last ten years, new techniques have been developed to evaluate the mechanical properties of biological tissues in vivo. To address this need, we employed a new instrument that, via the combination of micro-indentation with Optical Coherence Tomography (OCT), allows us to determine both, the spatial distribution of mechanical properties of chick embryos and the structural changes in real-time provided by OCT. We report here the stiffness measurements on live chicken mesoderm during somite formation, from the mesenchymal tailbud to the epithelialized somites. The storage modulus of the mesoderm increases from (176{+/-}18) Pa in the tail up to (716{+/-}117) Pa in the somitic region. The midline has a storage modulus of (947{+/-}111) Pa in the caudal presomitic mesoderm, indicating a stiff rod along the body axis, which thereby mechanically supports the surrounding tissue. The difference in stiffness between midline and presomitic mesoderm decreases as the mesoderm forms somites. The viscoelastic response of the somites develops further until somite IV, which is commensurate with the slow process of epithelization of somites between S0 and SIV. Overall, this study provides an efficient method for the biomechanical characterization of soft biological tissues in vivo and shows that the mechanical properties strongly relate to different morphological features of the investigated regions.

developmental biology↗

bioRxiv2019

Micro-indentation and optical coherence tomography for the mechanical characterization of embryos: Experimental setup and measurements on fixed chicken embryos.

Summary statementWe introduce an experimental technique that combines micro-indentation and optical coherence tomography to map the viscoelastic properties of embryonic tissue and investigate correlations between local mechanical features and tissue morphology. AbstractThe investigation of the mechanical properties of embryos is expected to provide valuable information on the phenomenology of morphogenesis. It is thus believed that, by mapping the viscoelastic features of an embryo at different stages of growth, it may be possible to shed light on the role of mechanics in embryonic development. To contribute to this field, we present a new instrument that can determine spatiotemporal distributions of mechanical properties of embryos over a wide area and with unprecedented accuracy. The method relies on combining ferrule-top micro-indentation, which provides local measurements of viscoelasticity, with Optical Coherence Tomography, which can reveal changes in tissue morphology and help the user to localize the indentation locations. To prove the working principle, we have collected viscoelasticity maps of fixed HH11-HH12 chicken embryos. Our study highlights the nonlinear behavior of the tissue and qualitatively shows the correlation between local mechanical properties and tissue morphology for different regions of interest.

developmental biology↗

bioRxiv2017

Mechanical stretching can modify the axial morphology of early chick embryos

Physical cues, experienced during early embryonic development, can influence species-specific vertebral numbers. Here we show that mechanical stretching of live chicken embryos can induce the formation of additional somites and thereby modify early segmental patterning. Stretching deforms the somites, and results in a cellular reorganization that forms stable daughter somites. Cells from the somite core thereby undergo mesenchymal-to-epithelial transitions (MET), thus meeting the geometrical demand for more border cells. Using a Cellular Potts Model, we suggest that this MET occurs through lateral induction by the existing epithelial cells. Our results indicate that self-organizing properties of the somitic mesoderm generate phenotypic plasticity that allows it to cope with variations in the mechanical environment. This plasticity may provide a novel mechanism for explaining how vertebral numbers in species may have increased during evolution. Additionally, by preventing the formation of transitional vertebrae, these self-organization qualities of somites may be selectively advantageous.

developmental biology↗