Homeostatic mechanics for a synthetic cell: predictions on substrate anisotropies and cell-cell interactions

Abstract

There has been a recent explosion in the design and development of functional and patient specific biocompatible and bioactive tissues. As the field of regenerative medicine progresses, the parameters required to control the bioreactors used to produce these tissues increase in number. Each parameter influences one or more biological processes, which in cells are known to be highly coupled. This added complexity limits the control over the biocompatibility and biofunctionality of the designed tissues. Amongst the many degrees of freedom in question, substrate topological and mechanical properties, as well as cell seeding density, stand out as critical design parameters to ensure the correct functionality of lab generated tissues. Given all these complexities, this research field is fertile for representative theoretical frameworks that can ultimately provide the ideal parameter values for an optimised bioreaction. While significant advances have been made in the field of biophysics, a theoretical framework capable of capturing the statistics of the cell’s fluctuating dynamic response to fixed values of controllable macrovariables remains elusive. In this work, we perform large scale numerical analyses and theoretical investigations by extending the Homeostatic Ensemble framework to elucidate the elusive physics and key parameters guiding cell response to a diverse set of cues. We first proceed to extend the framework to a non-equilibrium setting to capture the evolution rates governing cell morphological shape change. Thanks to the physics of the model, we discuss how the interplay between these morphological timescales and cell motility ultimately lead to contact guidance for single adherent cells on fibronectin lines. We then proceed to analyse contact guidance of a different nature, contact guidance due to the heterogeneity of substrate elasticity, to uncover and analyse the different guidance regimes governing cell alignment in this setting. Additionally, the findings obtained by introducing a theoretical model for focal adhesions reveal the interplay between cell mechano-sensitivity and substrate ligand depletion. Finally, we extend the Homeostatic Ensemble to the case of multiple adherent cells to capture the entropic nature of cell-cell interaction that modulates the response of cells to different substrate stimuli. From these findings, it emerges that cells feel and react to each other as if they were soft boundaries. This extended framework is envisioned as a “synthetic cell”, which is an in-silico version of biological cells, and is a viable candidate for the characterisation and design of the parameters controlling bioreactors.