Abstract 137: Sox6 Regulates Renin Expression During Juxtaglomerular Cell Expansion

Abstract

Introduction: Hypertension, a common condition that affects 33% of the US population, is a major risk factor for heart disease and stroke. Treatments for hypertension are limited and there is a critical need to develop new therapies. The Renin Angiotensin Aldosterone System (RAAS) plays a key role in regulating blood pressure, and renin controls its rate-limiting step. In adults, renin is produced and stored by renal Juxtaglomerular (JG) cells. During sodium restriction and other pathophysiological stresses that require an increase in renin expression and release, the adult kidney increases the number of cells expressing renin, in a process known as JG cell expansion. JG cells formation mechanisms remain unclear. Our aim is to determine new regulators of renin and blood pressure control. Methods: In vivo: JG cell expansion was induced by 10 days of low sodium diet (0.01% Na) and furosemide (0.1 mg/g body weight). In vitro: primary renal Mesenchymal Stromal Cells (MSC) were isolated from wild type mice and used until passage 5. MSC were differentiated into renin expressing cells by 7 days I&F (IBMX-100 uM and Forskolin-10 uM) treatment. Sox6 was down regulated in MSCs with lentivirus carrying vectors for Sox6 shRNA or controls scramble shRNA. Results: In vitro, I&F induced renin expression in MSCs (Renin relative expression to gapdh 0.0153±0.005, n=3, P= 0.05, no renin expression in MSCs). Gene arrays comparing renal MSCs and JG cells identified Sox6 as a potential gene that controlled MSC differentiation. In vitro silencing of Sox6 by shRNA inhibited the differentiation of renal MSCs into renin producing cells (3.5 fold decrease compared to control shRNA, n= 4, P= 0.01). In a new transgenic mouse model, in which Sox6 is deleted specifically in renin expressing cells (Ren1d Cre /Sox6 fl/fl ), plasma renin concentration was not affected at baseline (0.3 vs W.T. 0.5 ug Ang I/ml/h, n=3, P>0.05). However, under conditions that promote JG cell expansion, Sox6 ablation halted the increase in the number of JG cells (8.75 fold decrease, n= 6 to 9, P= 0.001). Conclusion: Our data indicates that Sox6 plays a novel role in renal physiology; modulating renin expression during pathological conditions. These findings suggest that Sox6 may become a new target for blood pressure control.