Development of urinary exosomes as biomarkers of drug-induced kidney injury

Aims

This project aims to develop the use of urinary exosomes as a non-invasive approach to assessing renal toxicity.

Background

Renal toxicity is estimated to account for around 2% of drug attrition in preclinical development and 19% in phase III clinical trials. Improving the identification of kidney toxicity and to ensuring better translation of biomarkers has the potential to reduce and refine the use of animals.

Damage to the kidneys as a result of drug toxicity is assessed as part of preclinical studies in animals. They tend not to be standalone studies unless a specific toxicity has been identified which requires further investigation. Assessment typically focuses on circulating biomarkers of kidney damage such as serum creatinine levels and post-mortem tissue analysis, however, these provide little information on the cellular site of injury or the underlying pathophysiology.

The use of urinary exosomes provides an opportunity to non-invasively investigate renal toxicity. This has a number of 3Rs advantages; early signs of renal toxicity should allow decisions to be made to terminate studies before animals suffer, and longitudinal studies in the same animal should be possible allowing animals to be used as their own control. Importantly, improved biomarkers which translate to the clinic should allow drugs to be dropped earlier in the pipeline before the extensive animal testing required to support late stage clinical trials.

Research details and methods

Exosomes are nanoparticle-sized vesicles which transport a range of molecules including microRNAs. They are derived from derived from a range of cells and released into blood and urine. This research aims to investigate whether rat urinary exosomes can be used as a non-invasive marker of renal toxicity.

Urinary exosomes have been shown to capsulate microRNA originating from the glomerulus and nephron. Recent evidence suggests that microRNAs are mediators of drug toxicity and therefore may provide potential biomarkers of cell injury. The research will explore the utility and reproducibility of urinary exosomes for analysis of kidney toxicity. It will employ nanoparticle tracking analysis technology and antibody labelling to identify exosome concentration and cellular origin.

A major reason why new drugs, that are promising in models of disease, do not reach patients is that they are toxic to the kidneys. To detect kidney damage and allow the safe design of human clinical drug trials the use of animals is essential. At present it is necessary to harvest kidney tissue from culled animals to identify which part of the kidney is injured and measure changes in key toxicity pathways. We propose to develop tiny particles released into the urine (exosomes) as a non-invasive alternative to using kidney tissue. This will reduce the number of animals used in kidney toxicity studies, and improve the quality of the studies, by allowing repeat measurements in the same animal and facilitate direct translation of rodent toxicity signals into human clinical trials. Specifically, we will use a new technology called nanoparticle tracking analysis (NTA) to determine if the number or cellular origin of rat urinary exosomes changes following exposure to the toxic cancer drug cisplatin. Exosomes are packets of information, for instance they contain microRNA, a new class of marker for drug induced organ injury. We will determine if the microRNA in exosomes changes when kidney tissue microRNA is up-regulated by drug toxicity – i.e. can exosomes replace the need for tissue? Finally, exosomes can transfer their information between cells. Using a cell model in place of animals, we will explore the mechanism of this new cell to cell signalling process.

• 2017 PhD Studentship Review: Case Study