Heat shock protein 72 (Hsp72) specific induction and temporal stability in urine samples as a reliable biomarker of acute kidney injury (AKI)

Abstract

We demonstrated that urinary heat shock protein of 72 KDa (Hsp72) is a sensitive biomarker for the early detection of acute kidney injury (AKI). However, whether Hsp72 induction during an AKI episode is kidney-specific is unknown, as well as, the degree of Hsp72 stability in urine samples. In rats that underwent bilateral renal ischemia and reperfusion (I/R), Hsp72 levels were evaluated in several tissues and in collected urines under different storage and temperature conditions, as well as in variable numbers of freeze-thaw cycles. The effect of room temperature and five freeze-thaw cycles on urinary Hsp72 levels was also evaluated in urine samples from AKI patients. We found that Hsp72 increased exclusively in the renal cortex of I/R group, emphasizing its performance as an AKI biomarker. Urinary-Hsp72 remained constant at room temperature (48 h), during 9 months of storage and was not affected by five freeze/thaw cycles.

• Ischemia/reperfusion
• renal cortex
• renal dysfunction
• tubular injury

In summary, our results indicate that urinary Hsp72 is a specific and a reproducible indicator of AKI for samples stored over several months and during short storage at room temperature or when the samples are exposed to several cycles of freezing/thawing.

Declaration of interest

NAB and JBC are inventors of Hsp72 patents. This project was supported through grants from the Mexican Council of Science and Technology (CONACyT 235855 and 181267 to NAB) and the National University of Mexico (IN223915 to NAB). We are grateful to Martha Carrrasco for her technical assistance. The results presented in this paper have not been published previously.