MECHANISMS OF AGE-and SEX- DEPENDENT CHANGES IN URINARY BLADDER IMMUNITY

PROJECT SUMMARY Urinary tract infections (UTIs) exhibit one of the most significant sex disparities among infectious diseases with UTIs in women being 20-40 times more likely than in men. In addition, 25-50% of elderly women suffer from recurrent UTIs (rUTIs) despite taking antibiotics, and over 25% of all elderly women experience persistent inflammation and lower urinary tract conditions such as overactive bladder/urge incontinence and interstitial cystitis/bladder pain syndrome. Given the strong association between bladder diseases and aging, and the fact that chronic bladder inflammation is highly prevalent in older women, age-associated immune disruption (so- called inflamm-aging) in the bladder likely mediates rUTI susceptibility. With 566 million people ≥65 years old worldwide and estimates of nearly 1.5 billion by 2050, there is a growing need to define the interactions between aging, chronic inflammation, and susceptibility to UTIs/rUTIs so that better treatments and prevention of these diseases will be possible. The hypothesis of this project is that the culprit behind many rUTI cases and lower urinary tract symptoms is a chronic inflammatory process characterized by organized lymphocytic aggregates in the bladder submucosa, termed bladder tertiary lymphoid tissue (BTLT). These are analogous to lymphocytic infiltrates in women presenting as cystitis cystica (CC) by cystoscopy. We have demonstrated that BTLT/CC are predominantly in women and female mice and are sites of antigen presentation, germinal center formation, and antibody production, and form in an age-dependent and sex-dependent manner. Despite this understanding, the mechanisms driving BTLT formation, maintenance, impact on rUTIs, and sex dependence are unknown. Using a mouse model of aging and chronic bladder infection and inflammation that closely parallels the clinical presentation of post-menopausal women with UTIs, we will elucidate the underlying immune and hormonal drivers that cause frequent recurrent UTIs and heightened lower urinary tract symptoms in a sex-dependent manner. Specifically, we will define the molecular drivers (Aim 1) and investigate the role of CXCL13, TNFα, and FCRL5 in BTLT initiation, maintenance, and structure will be investigated through targeted interventions in aged mice; Explore the role of BTLT in immune responses during UTI by depleting B cells and profiling B cell receptor repertoires, identifying clonotypes involved in UTI defense. (Aim 2); determine the cause-and-effect association between BTLT/CC and rUTIs; and define the influence of sex and estrogen on BTLT formation (Aim 3). This new concept of the interplay between aging, sex, infection, and local immune responses within the bladder generates many new important questions for the field. By elucidating the mechanisms, mediators, and triggers that drive BTLT formation, taking into consideration sex differences, this work will provide important insights into mucosal immunity in the aging bladder. Additionally, this work will establish the foundation for future development of biomarkers of functional immune system changes in older individuals to guide treatment strategies aimed at improving infection and inflammation outcomes.