Exploring the urobiome’s influence on kidney health and transplant

Rationale: The urobiome's impact on renal health remains underexplored in kidney transplant patients. Considering the kidney-urine connection and the need for strategies to enhance allograft longevity, further investigation is essential. This thesis examines the relationship between urinary microbes and kidney health, focusing on two main aims: 1. Characterize the urobiome in renal transplant patients during health and disease. 2. Assess the impact of lipopolysaccharide (LPS) and lipoteichoic acid (LTA) on kidney cells. Methods: Aim 1: Urine samples from local transplant patients, with and without acute cell-mediated rejection, were profiled using 16S rRNA sequencing. Aim 2: Utilize an in vitro model to examine the effects of bacterial cell membrane components (lipopolysaccharide and lipoteichoic acid) on kidney mesangial and tubular cell lines. Metabolic activity, cell death, and cytokine production were analyzed. Results: Aim 1: Kidney transplant patients exhibited a general loss of taxa post-transplant. The rejection group showed increased Corynebacterium, while non-rejectors had more Bifidobacterium and Peptoniphilus. Post-transplant microbiomes contained ~75% unique taxa compared to pre-transplant samples. Aim 2: LPS or LTA stimulation led to a dose-dependent decline in kidney cell metabolic rates and increased inflammatory gene expression. Combining LPS and LTA preserved metabolic rates and reduced overall gene expression. Apoptosis was not significantly induced. Conclusion: Clinical data suggests that renal transplantation has a profound impact on an individuals’ urobiome composition. It is possible that the urobiome from the donor is transplanted along with the kidney, which could explain the stark differences seen pre to post transplant (~75% turnover). While the specific urobiome factors that differentiate rejectors and non-rejectors remain unknown based on current data, our findings suggest that dysbiosis contributes to pathologic states, which is consistent with prior literature. Our laboratory studies confirmed that LPS and LTA both act as stressors to kidney cells. When combined, they seem to have a modulating effect that decreases their joint toxicity, shown in both metabolic studies as well as gene expression. This supports the potential protective functions of a diverse microbiome on renal health in both transplant and non-transplant patients.