Klotho inside uEVs and its potential role as biomarker for kidney physiopathology

Entering an era in which biomarkers are gaining considerable importance in the clinical world, we decided to investigate Klotho levels as an efficient indicator of the overall state of the kidneys. In this study, we focus on the expression of Klotho, an anti-aging hormone released by the kidney, within urinary extracellular vesicles (uEVs). Our analysis strategy focuses on two different conditions: the first one aims to assess whether variations in Klotho concentration could be correlated to cardiac surgery associated acute kidney injury (AKI), one of the most common serious complication that may occur after cardiac surgery. The second condition taken into account is the so called “single ventricle defect” - a rare pathology that affects about five out of 100,000 newborns and isstill largely unknown, particularly in the context of renal function after palliative surgical intervention referred as Fontan. Very little is known about how this condition may impact kidney function; however, decrease in eGFR levels and tubular injury have been suggested. In this study we isolated and characterized uEVs, combining the cytofluorimetric analysis of uEV surface markers, obtained with MACSplex Exosome Kit, with the quantification of uEVs-Klotho measured by ELISA. Moreover, Klotho and classical exosomal and renal markers were confirmed by single-molecule super resolution microscopy. The results, although preliminary, suggest that Klotho expression might be a relevant biomarker to assess renal function in patients after cardiac surgery. Additionally, the reduction in uEVs-Klotho levels could be indicative of the decline in kidney function in patients with single ventricle defects.