Abstract
The mechanical properties of tissues are pivotal for morphogenesis and disease progression. Recent approaches have enabled measurements of the spatial distributions of viscoelastic properties among embryonic and pathological model systems and facilitated the generation of important hypotheses such as durotaxis and tissue-scale phase transition. There likely are many unexpected aspects of embryo biomechanics we have yet to discover which will change our views of mechanisms that govern development and disease. One area in the blind spot of even the most recent approaches to measuring tissue stiffness is the potentially anisotropic nature of that parameter. Here, we report a magnetic micromanipulation device that generates a uniform magnetic field gradient within a large workspace and permits measurement of the variation of tissue stiffness along three orthogonal axes. By applying the device to the organ-stage mouse embryo, we identify spatially heterogenous and directionally anisotropic stiffness within the mandibular arch. Those properties correspond to the domain of expression and the angular distribution of fibronectin and have potential implications for mechanisms that orient collective cell movements and shape tissues during development. Assessment of anisotropic properties extends the repertoire of current methods and will enable the generation and testing of hypotheses.
Highlights
The generation of tissue shape has long been recognized as a mechanical process [1, 2]
We developed a new multipole magnetic tweezer device that generates a uniform magnetic field gradient within a fivefold larger workspace compared to the previous iteration [7]
Since it was shown that fibronectin mRNA exhibited a distally biased localization in the mandibular arch [40], we examined the fibronectin expression by immunostaining
Summary
The generation of tissue shape has long been recognized as a mechanical process [1, 2]. The elastic and viscous properties of tissues and forces generated by cells have been implicated in morphogenetic processes. Convergent extension is a fundamental morphogenetic process that narrows and elongates many different tissues during multiple stages of development (e.g., gastrulation, neurulation, axis elongation, and organogenesis) [15]. It is unclear whether directionally biased or anisotropic viscoelastic properties promote or result from convergent extension, owing largely to the lack of tools to measure anisotropic properties in vivo
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