A microfluidic human 'pelvis-on-a-chip' model to study ascending urinary tract infection

Why did we fund this project?

This award aims to develop a ‘pelvis-on-a-chip’ using human gut, bladder, ureter, and kidney organoids to replace the use of some animals in urinary tract infection (UTI) research.

With an estimated 150M global cases each year, UTIs are the most common bacterial infection and the leading cause of septicaemia. They are a key driver of antimicrobial resistance with more than a quarter of UTIs recurring despite antibiotic treatment. As UTIs progress, bacteria travel through multiple organs each with a unique microenvironment with specific host/pathogen interactions, bacterial behaviour and antibiotic susceptibility. In vivo studies predominantly involve mice (and also pigs) and can involve infecting animals with high doses of bacteria through a catheter and culling following weeks of active infection. Organoids are available but they lack the complexity required to model the spread of infection through multiple organs. The student, with Professor Jennifer Rohn, will develop a more relevant in vitro model of ascending UTIs by creating a ‘pelvis-on-a-chip’ with multiple organoids linked by microfluidic channels. This system will mimic flow through the urinary tract, enabling host cell and uropathogen behavioural studies and trials for new UTI antimicrobials.

With 150 million cases annually, urinary tract infection (UTI) imposes an enormous healthcare and economic burden. Unfortunately, traditional antibiotics are suboptimal, with one in four infections recurring within six months, sometimes for years. This cycle of futile treatment fuels the antimicrobial resistance (AMR) crisis, one of the greatest threats we face as a global community. While COVID has distracted the world, the seemingly unstoppable evolution of drug-resistant bacteria could leave us without viable treatments for even the most trivial infections within the next three decades. AMR already kills millions each year, but if nothing is done, drug-resistant infections could cause 10 million deaths each year by 2050 and an annual economic cost of 69 trillion GBP. Therefore, we urgently need to better understand UTI pathophysiology and to create relevant disease models to catalyze more effective, non-antibiotic-based treatments.

The vast majority of UTI research has relied on mouse models, mostly in the 'moderate severity' category, in which animals are infected for long periods of time. However, rodents are not naturally susceptible to UTI; while 'forced-infection' models have provided important insights, key species differences exist, and their consequences are largely unknown. The pig model is more relevant, but is expensive and less tractable. Recent advances in human cell-based in vitro models of the main uropathogen reservoirs - gut, bladder and kidney - are promising, but they allow infection to be studied only in silos, whereas natural UTI involves transit of bacteria, from gut to urethra to bladder, and sometimes further into the kidney, with behaviour and gene  expression modified dynamically during this journey.

We propose to capitalise on a renaissance in 'body-on-a-chip' technology, where different tissue organoids are linked via microfluidic chambers, to create a human 'pelvis-on-a-chip' (POAC) platform comprising gut, bladder, ureter and kidney organoids. To our knowledge, such a system has never before been reported. Not only would this novel device allow the seamless transit of bacteria, but the fluid-flow component of microfluidics would emulate urine flow patterns, which are known to affect both host cell and bacterial behaviour. We propose to leverage our specialist knowledge of organoid models and microfluidics to (1) create the POAC; (2) study ascending bacterial infection within the POAC; and finally (3) trial at least one novel antimicrobial strategy to assess its utility as a therapy testbed.

The POAC aims to replace some animal use in UTI research, where it may be more physiologically meaningful for certain parameters (e.g. at the host cell/pathogen interface); and in drug discovery and testing where systemic/immune responses are not required. Such replacement would lead to some reduction in overall animal use. Locally, our lab does not use animals, but we calculate, based on PubMed searches, papers and personal communications with UTI mouse researchers that, with predicted 30% replacement internationally, our model could spare up to 3000 mice per year. These numbers could be even higher with uptake from researchers who study indications outside of UTI, such as bladder cancer, overactive bladder, and interstitial cystitis/bladder pain syndrome.

Aside from dissemination in open-access preprint servers, publications and genomic data repositories, we will create a lasting 3Rs legacy by constantly updating our protocols and making them freely available to the community on our website and via the NC3Rs Gateway. As with our existing bladder model, we will continue to work personally with any researcher who wants to set up the POAC in their own lab, including hosting visiting scientists. We will also organize a high-profile conference of key international stakeholders, including existing mouse UTI researchers, to showcase the exciting potential of alternative models.