Title: Development of urinary exosomes as biomarkers of drug-induced kidney injury
Funder: National Centre for the Replacement, Refinement and Reduction of Animals in Research

Abstract: The kidney is often affected by drug toxicity, this being a frequent reason for promising drugs to fail to reach humans. Rodent models are an essential part of pre-clinical testing for kidney toxicity. Current circulating biomarkers such as serum creatinine are slow to report injury and do not provide information regarding the cellular site of injury or the underlying pathophysiological process. Therefore, post-mortem analysis of kidney tissue is essential which prevents repeated measurements on the same animal. This cross-sectional design is sub-optimal: important information concerning the temporal progression of disease can be lost and the total number of animals required for any given study is high. Furthermore, tissue biomarkers have limited translational utility since renal biopsies usually cannot be performed in phase 1 clinical trials. Our objective is to refine the approach for drug toxicity studies by developing urinary exosomes (a specific type of cell-derived nanoparticle) as a reservoir for non-invasive sampling of kidney tubular cell microRNA (miRNA). This approach is designed for longitudinal studies: the ability to make repeated measurements as injury progresses promises to reduce the total number of animals required yet provide more informative and translatable data. Exosomes are vesicles formed within cells that are released into biological fluids such as urine. Urinary exosomes encapsulate miRNA originating from cells of the kidney’s glomerulus and each region of the nephron. MiRNA are promising new biomarkers of cell injury because organ-specific miRNA species are released from cells following injury and they are stable in a range of biofluids including urine. The first aim of this studentship is to characterize the rat urinary exosome population and determine the effect of nephrotoxic AKI on exosome excretion. We will use a new technology, nanoparticle tracking analysis, that can directly measure urinary exosome concentration and, in combination with antibody labeling, identify the exosomal cell of origin. Our hypothesis is that exosomes will be released by injured tubular cells and create a toxicity signal in the urine. Our second aim is to determine if changes in kidney tissue miRNA are faithfully reflected in exosomes and, therefore, whether exosomes could replace the need for post-mortem tissue and allow non-invasive, repeat miRNA sampling. Our third aim is to explore the biological function of exosomes as inter- cellular signals in a kidney cell model. Exosomes shuttle protein, messenger RNA (mRNA) and miRNA between cells. This can change the proteome, and therefore function, of the recipient cell either directly by protein transfer, or indirectly via translation of exosomal mRNA or miRNA interference of target proteins. With exosomes released into the urine along the entire renal tubule, the capacity to traffic downstream protein or RNA species and thereby influence cell physiology is a novel mechanism for signaling within the kidney.


Research activity codes: 5.1 PHARMACEUTICALS;5.9 RESOURCES AND INFRASTRUCTURE (TREATMENT DEVELOPMENT)
Health categories: RENAL AND UROGENITAL