Urinary extracellular vesicular release of aquaporins in patients with renal transplantation

• Published in: BMC nephrology 2019-06, Vol.20 (1), p.216-7, Article 216
• Main Authors: Oshikawa-Hori, Sayaka, Yokota-Ikeda, Naoko, Sonoda, Hiroko, Ikeda, Masahiro
• Format: Article
• Language: English
• Subjects: Adult; Allografts; Analysis; Aquaporin 1; Aquaporin 1 - metabolism; Aquaporin 2; Aquaporin 2 - metabolism; Aquaporins; Biomarkers; Biotechnology; Centrifugation; Diuresis; Extracellular vesicles; Extracellular Vesicles - metabolism; Female; Gene expression; Homeostasis; Homografts; Humans; Immunoblotting; Ischemia; Kidney; Kidney diseases; Kidney Failure, Chronic - surgery; Kidney transplantation; Kidney Transplantation - adverse effects; Kidney Transplantation - methods; Male; Middle Aged; Nephrology; Patient outcomes; Postoperative Care - methods; Postoperative Complications - diagnosis; Postoperative Complications - etiology; Postoperative Complications - metabolism; Proteins; Reabsorption; Renal Reabsorption - physiology; Renal transplantation; Sodium; Studies; Surgery; Transplants & implants; Urinalysis - methods; Urine; Water; Water-Electrolyte Imbalance - diagnosis; Water-Electrolyte Imbalance - etiology; Water-Electrolyte Imbalance - metabolism
• ISSN: 1471-2369; 1471-2369
• DOI: 10.1186/s12882-019-1398-7

Diuresis has been observed within a week following renal transplantation, suggesting that the procedure causes acute disturbance of renal water homeostasis. Aquaporin (AQP) 1 and AQP2, important proteins for renal water reabsorption, have been identified in urinary extracellular vesicles (uEV-AQP1 and -AQP2), and experimental studies have shown that the presence of uEV-AQP1 and -AQP2 may be an indicator of their levels of expression in the kidney. However, the release patterns of uEV-AQP1 and -AQP2 during the acute phase following renal transplantation are largely unknown. In this study, we examined the release of uEV-AQP1 and -AQP2 in recipients until 6 days (day 6) after renal transplantation. At Miyazaki prefectural Miyazaki Hospital, Japan, uEVs were obtained from 7 recipients, all of whom had received renal allografts from living donors. uEVs were isolated by differential centrifugation. Immunoblotting analysis showed that the release of uEV-AQP2 was significantly decreased on day 1 in comparison with a control sample (from 3 healthy volunteers), accompanied by high urine output and low urine osmolality. Thereafter, the level increased gradually to the control level by day 6. The release pattern of uEV-AQP1 was similar to that of uEV-AQP2, but the levels did not reach statistical significance in comparison with the control level at any of the time points examined. Evaluation of the relationship between urinary osmolality and uEV-AQPs revealed a significant correlation for uEV-AQP2, but not for uEV-AQP1. These results indicate that acute diuresis after renal transplantation might be due to a decrease in the renal expression of AQP2, whose level can be estimated from the amount released in uEVs.