Renin-angiotensin system dysregulation in fetuses with hydronephrosis

The role of Plasma Renin Activity in prenatally diagnosed non-obstructed hydronephrosis at risk for surgery-an observational study

BACKGROUND

Patients with asymptomatic prenatally diagnosed hydronephrosis may progress to needing surgery; no biomarker supporting the identification of these cases is currently available. The aim of the study was to assess the role of Plasma Renin Activity (PRA) as a discriminatory factor to identify patients with asymptomatic prenatally diagnosed hydronephrosis who require close monitoring and are at-risk for surgery.

METHODS

The study group consists of 30 children prenatally diagnosed with asymptomatic unilateral hydronephrosis, initially managed with medical follow-up. Pyeloplasty was indicated if patients became symptomatic or if there was a significant drop in split renal function (SRF) during follow-up. An association was sought between PRA and renal parameters in post-hoc analysis.

RESULTS

During the mean follow-up of 55.5 ± 8.2 months, 13/30 (43.3%) patients developed delayed drainage and 8/30 (26.6%) underwent pyeloplasty. Mean PRA was higher at presentation in the group which later presented with a drop in differential kidney function  ≥ 10%, while it was within the normal range for age in the other patients. Before pyeloplasty, progression to delayed drainage coincided with a drop in SRF and a rise in PRA. While PRA levels normalized after pyeloplasty, SRF improved but did not reach initial values. A mean rise of 68.9% in PRA preceded current indications for surgery by 27.5 ± 9.5 months.

CONCLUSIONS

A progressive increase in PRA in children with asymptomatic prenatally diagnosed hydronephrosis reflects obstructive stress in the tubulo-interstitial compartment. This stress is relieved by pyeloplasty and is reflected by a drop in PRA after surgery. PRA can, thus, serve as the discriminatory factor to identify hydronephrosis patients 'at-risk' for surgery even before the current criteria for pyeloplasty are met.

Hydronephrosis alters cardiac ACE2 and Mas receptor expression in mice

INTRODUCTION

Hydronephrosis is characterized by substantial loss of tubules and affects renin secretion in the kidney. However, whether alterations of angiotensin-converting enzyme (ACE), ACE2 and Mas receptor in the heart are observed in hydronephrosis is unknown. Thus, we assessed these components in hydronephrotic mice treated with AT1 receptor blockade and ACE inhibitor.

MATERIALS AND METHODS

Hydronephrosis was induced by left ureteral ligation in Balb/C mice except sham-operated animals. The levels of cardiac ACE, ACE2 and Mas receptor were measured after treatment of losartan or enalapril.

RESULTS

Hydronephrosis led to an increase of ACE level and a decrease of ACE2 and Mas receptor in the heart. Losartan decreased cardiac ACE level, but ACE2 and Mas receptor levels significantly increased in hydronephrotic mice (p < 0.01). Enalapril increased ACE2 levels (p < 0.01), but did not affect Mas receptor in the heart. Plasma renin activity (PRA) and Ang II decreased in hydronephrotic mice, but significantly increased after treatment with losartan or enalapril.

CONCLUSIONS

Hydronephrosis increased cardiac ACE and suppressed ACE2 and Mas receptor levels. AT1 blockade caused sustained activation of cardiac ACE2 and Mas receptor, but ACE inhibitor had the limitation of such activation of Mas receptor in hydronephrotic animals.