Systems biology and mechanics of growth

Abstract

In contrast to inert systems, living biological systems have the advantage to adapt to their environment through growth and evolution. This transfiguration is evident in embryonic development, when the predisposed need to grow allows form to follow function. Alterations in the equilibrium state of biological systems breed disease and mutation in response to environmental triggers. The need to characterize the growth of biological systems to better understand these phenomena has motivated the continuum theory of growth and stimulated the development of computational tools in systems biology. Biological growth in development and disease is increasingly studied using the framework of morphoelasticity. Here we demonstrate the potential for morphoelastic simulations through examples of volume, area, and length growth, inspired by tumor expansion, chronic bronchitis, brain development, intestine formation, plant shape, and myopia. We review the sytems biology of living systems in light of biochemical and optical stimuli and classify different types of growth to facilitate the design of growth models for various biological systems within this generic framework. Exploring the systems biology of growth introduces a new venue to control and manipulate embryonic development, disease progression, and clinical intervention.

Mechanical properties of the airway tree: heterogeneous and anisotropic pseudoelastic and viscoelastic tissue responses

“…Previous studies highlighted the need for relevant experimental data to inform physiological models, especially for the bronchial tree (17,45,48,57). Past studies extensively investigated the buckling and folding behavior of the airways due to inflammation and bronchoconstriction in diseases such as asthma and bronchitis, since the effect is directly tied to airway resistance (4,16,53). Complex models have evolved from simplified analytical models to computational optimization to personalized magnetic resonance images informing patient-specific geometries (15,29,35,38,40,65); yet all of these studies highlighted limitations due to the lack of regional airway material properties and resorted to utilizing generic constitutive laws.…”

Modified multiplicative decomposition model for tissue growth: Beyond the initial stress-free state

“…Here we adopt the constant growth rate model presented by Eskandari and Kuhl (2015) and the logarithmic distribution of initial stress in the reference configuration given by Eq.(27). Hence, the components of the growth deformation gradient tensor at time t are g r (t) = 1 +ġ r t, g θ (t) = 1 +ġ θ t,…”

Elastosis during airway wall remodeling explains multiple co-existing instability patterns

“…We assume that the airway wall grows morphogenetically and isotropically [24, 32]. We prescribe the growth tensor F g as the identity tensor I scaled by the growth multiplier ϑ [27],…”