Study finds that extracellular vesicles from stored cat urine had differential protein expression between cats with normotensive chronic kidney disease (CKD) and hypertensive CKD

24 January 2023

A new study published in the latest issue of the Journal of Small Animal Practice (JSAP) successfully isolated extracellular vesicles from stored cat urine, and showed that the vesicles had differential protein expression between cats with normotensive chronic kidney disease (CKD) and hypertensive CKD. Urinary extracellular vesicles, which originate from the kidney, are a potential source of biomarkers that could be used to understand the pathogenesis of feline CKD and hypertension.

In the study titled “Urinary extracellular vesicles as a source of protein-based biomarkers in feline chronic kidney disease and hypertension”, ultrafiltration and exclusion chromatography were initially identified as the optimal method of feline extracellular vesicle isolation, obtaining the highest purity and expected size and morphology compared with two alternative methods.

This technique was then used to isolate extracellular vesicles from urine samples from cats with normal renal function, normotensive CKD and hypertensive CKD. Cats were classed as having normal kidney function based on creatinine and urine specific gravity, and normotensive or hypertensive based on systemic blood pressure and/or ocular target organ damage.

Nanoparticle tracking analysis found no significant difference in the mean diameter or concentration of extracellular vesicles isolated from cats with and without CKD, suggesting that their size and concentration are unaffected by renal disease and hypertension. Subsequent proteomic analysis using liquid chromatography and tandem mass spectrometry showed no differential protein expression between the extracellular vesicles of healthy cats and those in the CKD category. However, extracellular vesicles from cats with hypertensive CKD showed differential expression of five proteins compared with extracellular vesicles from cats with normotensive CKD. These included significantly increased expression of aminopeptidase and significantly decreased expression of alpha-2-macroglobulin, cauxin, inter-alpha-trypsin inhibitor heavy chain 4 and transferrin.

The authors commented that further investigation into the utility of these differentially expressed proteins as biomarkers or therapeutic targets is warranted to determine if altered expression correlates with disease pathogenesis.

Nicola Di Girolamo, Editor of JSAP concluded: “CKD is particularly common in geriatric cats and associated hypertension can contribute to morbidity, so the search for factors associated with disease is highly valuable.”

The study was funded by BSAVA PetSavers, the grant awarding arm of the British Small Animal Veterinary Association. This is supported solely by charitable donations and has invested more than £2 million in vital clinical research and training programmes over the past 40 years to advance clinical investigations into pet animal medicine and surgery. For further information visit:

The full article can be found in the January issue of the Journal of Small Animal Practice and can be read online here: