(512d) In Vitro Recapitulation of Collective Dynamic Mucus Barrier Complexity

The mucus lining along the gastrointestinal tract is the outermost and largest interface in the body that protects the epithelium, regulates the selective transport of nutrients, and maintains a sterile relationship with microbes. Despite its importance, the mucus barrier has been understudied due to the lack of relevant experimental models. Here, we introduce a functional and analytical mucus barrier model enabled by the development of tissue-inspired simple and scalable mucin extraction method. Retrieved mucins preserved intrinsic biochemical and biophysical characteristics. Reconstituted mucins formed layers that recapitulated pH and Ca²⁺ dependent barrier properties and associated molecular transport and bacterial motility. At neutral pH, the thickness of the mucus barrier linearly increases as a function of Ca²⁺, but the increased thickness does not necessarily decrease mucus transport. Intriguingly, there exists an optimal Ca²⁺ concentration that maximally inhibits transport in which the mucus barrier forms a coacervate-like phase; densely packed small aggregates of mucin-Ca²⁺ complexes minimize the interstitial space for percolation. This observation explains how secreted mucins collectively and autonomously regulate barrier properties in response to continually evolving luminal biochemical milieu. We envision that the established methods facilitate various aspects of mucus barrier research in health and disease with higher physiological complexity.