Title : A NAMs-compatible mechanopharmacological model of drug penetration in the urinary bladder
Abstract:
Conventional antibiotic efficacy metrics fail to capture the mechanopharmacology of bladder infections, where pathogens persist within protected intracellular and subepithelial reservoirs that drive chronic disease. The bladder uroepithelium is a stratified, mechanosensitive barrier undergoing cyclic stretching during filling and voiding, which dynamically shapes drug transport. Advances in microphysiological bladder systems demonstrate that cyclic strain modulates junctional integrity, vesicular trafficking, and drug penetration, thereby influencing bacterial persistence. Building on these insights, the three dimensional urine tolerant human uroepithelial model (3D-UHU) provides a stratified, tight epithelium suitable for studying mechanics dependent drug transport and infection dynamics. However, current bladder microtissue platforms lack integrated pharmacokinetic components required for quantitative efficacy assessment, despite advances in pharmacological modeling using human organ-chip systems. Here, we present a mechanopharmacological PBPK-PD framework compatible with New Approach Methodologies (NAMs), aligned with FDA goals to reduce animal testing and advance human microphysiological models, linking bladder mechanics to spatially resolved drug penetration and bacterial clearance.
Drug transport across the uroepithelium is modeled through coupled transcellular and paracellular fluxes from the urinary lumen to plasma across a multilayer barrier. Urine and plasma are treated as well-mixed compartments, while spatial concentration gradients across epithelial layers are resolved using a resistive network. Cyclic bladder strain modulates effective drug permeability via a strain-dependent penetration factor, capturing enhanced penetration during filling and restoration of barrier resistance during voiding. Layer-specific accumulation factors represent intratissue drug retention and heterogeneous exposure.
To support in silico predictions, the PBPK-PD framework is integrated with the 3D-UHU platform. We evaluate how antibiotic pharmacokinetics and mechanics-dependent tissue penetration shape bacterial clearance across the stratified uroepithelium for three clinically relevant antibiotics. Simulations show that mechanics-driven transport generates subtherapeutic microenvironments in deeper layers, limiting bacterial clearance despite equivalent luminal drug concentrations. This framework links tissue mechanics, transport, and persistence to antibiotic efficacy, supporting predictive, animal-free PBPK-PD assessment and mechanism-aware dosing across healthy and impaired tissue states, including fibrosis and cancer. These principles are readily extensible to the kidney and lung, motivating future development of analogous mechanopharmacological models in mechanically active epithelia.
