Formation of extracellular vesicles depends on mechanical feedback of the cortex and the glycocalyx

Cell-secreted extracellular vesicles (EVs) play a pivotal role in local and distant cell-to-cell communication by delivering specific cargoes to other cells or to the extracellular space. In many cells, the glycocalyx, a thick sugar-rich layer at the cell surface, and the membrane-cortex attachment are crucially linked to the formation of EVs, yet it is unclear what determines the successful formation of EVs when multiple physical factors are involved. In this work, we developed a model for glycocalyx-membrane-cortex composite to investigate the effects of gly-cocalyx and membrane-cortex adhesion on the formation of EVs by combining polymer physics-based theory and Helfrich membrane theory. By performing linear stability analysis, we show that modulating the mechanical feedback among the glycocalyx, membrane-cortex attachment, and membrane curvature can give rise to two types of instabilities: a conserved Turing-type instability and a Cahn-Hilliard-type instability. Furthermore, using an equilibrium model, we identified two critical conditions for EV formation: an initial detachment of the membrane from the underlying cortex and then a sufficient driving force to induce membrane deformation for successful EV formation. We further demonstrated that there exists an optimal glycocalyx coating area at which the formation of EVs is most favorable. Finally, we use our model to predict that a heterogeneous size distribution of EVs can be generated through the regulation of glycocalyx properties, shedding insight into how EVs of different radii may be generated. Significance StatementExtracellular vesicles (EVs) are important for cell biology because they facilitate active communication between cells. Understanding the governing factors that control the formation of EVs is crucial to many cellular processes ranging from tumor progression and metastasis evolution to the disposal of unwanted biomolecules. However, whether EV secretion is a consequence of the glycocalyx and the role of membrane-cortex adhesion in the formation of EVs are still elusive. To address these issues, here we develop a biophysical model for EV formation that couples the presence of glycocalyx and membrane-cortex adhesion. We find that the glycocalyx-membrane-cortex composite system exhibits two types of instabilities utilizing stability analysis - a Turing instability and a Cahn-Hilliard type instability. Based on our proposed equilibrium model, we identified that for the initiation of membrane detachment and the formation of EVs each need to meet a critical threshold. In addition, our model predicts that the formation of EVs is most favorable when an optimal glycocalyx coating area reaches and a heterogeneous distribution EV sizes can be produced by regulating glycocalyx properties.