Marco Tjakra: Artificial colonic mucus for studies of the mucus absorption barrier

Abstract

Colonic diseases affect more than 10 million people in Europe, and by 2045, more than 1% of the global population is expected to be affected by inflammatory bowel diseases. Drug development targeting colonic diseases is urgently needed. However, translating in vitro research into in vivo clinical relevance remains a challenge, with significant time and effort required in drug discovery and pre-clinical stages. Therefore, the development of efficient drug study platforms is necessary, in accordance with the ethical 3Rs principles and the UN SDGs 2030. In addition, the FDA Modernization Act 2.0 encourages the improvement of in vitro models with in vivo relevance.

Colonic mucus is the first interface in contact with drugs targeting colonic diseases. Mucus is a hydrogel composed of complex macromolecular crosslinks and acts as a structural barrier. In healthy conditions, colonic mucus consists of a stratified layer, with the outer layer hosting bacteria. Previous studies have reported changes in mucus in 85% of patients with various colonic diseases. However, characterization of the viscoelastic and barrier properties of colonic mucus in diseased states is still underexplored.

This PhD project focuses on studying the characteristics of the mucus barrier that may influence drug diffusion. Properties of native colonic mucus from human patients are characterized. Combined with studies of particle diffusion and viscoelastic properties in colonic mucus, general parameters influencing drug diffusion in the mucus are identified. Characteristics dependent on pH, surface charge, viscosity, and macromolecular composition of mucus have been investigated. Studies of drug interaction with mucus models from pig, dog, and artificial colonic mucus were performed to observe drug diffusion, drug binding, and drug permeability. Various methods to improve experimental (3D printing) and analytical (machine learning classifiers and physiology-based pharmacokinetic models) approaches were incorporated to enhance reproducibility and provide in-depth data analysis.

From this study, the macrorheology and microrheology profiles of the mucus were compared, and artificial colonic mucus was shown to capture the properties of native colonic mucus. By formulating a biosimilar artificial colonic mucus based on the native form, computational studies connecting to in vivo settings allow for better prediction and improved clinical relevance.