The Role of the Bladder Microbiome in Lower Urinary Tract Disorders

Lower urinary tract symptoms (LUTS) cumulate a multitude of syndromes and urinary tract infections (UTI). This thesis focuses principally on recurrent UTIs (rUTIs) in renal transplant recipients and overactive bladder (OAB). In many cases, the cause of OAB is unknown. Recent studies in bladder microbial investigation have proposed that low-level bacteriuria or alterations in the bladder microbiome may be a cause for the symptoms of this syndrome. This thesis sets out to investigate the types of bacteria in the bladder of women with OAB and renal transplant recipients compared to asymptomatic controls by culturing urine samples and using 16s rRNA gene sequencing to identify exact species in each sample. The data is analysed alongside clinical data to determine better biomarkers for both rUTI and OAB. The results highlight that current hospital tests for infection are underreporting low-level infection and many of the biomarkers for infection do not correlate with incidence of infection. Here, the use of clue cells as a biomarker for rUTI is investigated for the first time with optimistic results. Furthermore, the alterations of the bladder microbiome over time post-renal transplant highlight consistently reduced incidence of particular species indicating shifts in the bladder microbiome in these patients. Using similar methods to explore the microbiome of women with OAB, it was found that there is a significant reduction of Lactobacillus, a crucial probiotic in the urogenitary tract that may be key to shifts in the bladder microbiome in OAB. The final section attempts to explore the physiology behind the symptoms of OAB in light of recent findings associating bacteria to OAB by looking at pericytes (a peri-vascular cell type found on capillaries). Pericytes are capable of transdifferentiating into myofibroblasts, a fibrotic cell which may increase spontaneous contraction in the bladder. This section investigates pericytes behaviour in the bladder in response to ATP, angiotensin, lipopolysaccharide and pro-inflammatory cytokines in a series of DIC imaging and immunohistochemistry experiments. The data supports this theory since pericytes constrict vessels upon acute stimulation and pericyte numbers dwindle with prolonged exposure. In conclusion, this thesis highlights the importance of correct testing for bladder infections and suggests that shifts in the bladder microbiome may be a cause for some lower urinary tract symptoms and this could be caused by pericyte responses to ATP and downstream cytokines.