Abstract 153: Born with a Single Kidney versus Nephrectomy: Similar End Point, Different Mechanism of Injury
A relatively common abnormality of the urogenital tract in humans is the development of only a single kidney (1:500 to 1:1000). Clinical studies suggest that patients born with a single kidney can develop proteinuria, hypertension, and even renal failure later in life. In contrast, studies in children who undergo nephrectomy or adults who serve as kidney donors appear to exhibit little difference in renal function compared to two-kidney subjects. Invasive techniques such as nephrectomy or renal ablation have been used to generate animal models to recapitulate this human congenital disorder. The progression of injury in these models is attributed to hyperfiltration which refers to changes in hemodynamics that cause glomerular damage leading to hypertension. Recently, our lab developed a new genetic animal model [heterogeneous stock derived model of unilateral renal agenesis, (HSRA)] that develops with a single kidney in 50-75% of offspring. The model is characterized by reduced nephron number, kidney hypertrophy, and renal injury that leads to a decline in renal function. Time course evaluation of blood pressure, renal hemodynamics, and renal injury was performed in 4 groups; (1) HSRA-S (1-kidney), (2) HSRA-C (2-kidney littermates), (3) HSRA-UNX3 (uninephrectomy-week 3) and (4) HSRA-UNX8 (uninephrectomy-week 8). Nephrectomized animals demonstrated hyperfiltration, whereas single kidney animals (HSRA-S) did not. This suggests a different pathophysiological mechanism of injury between congenital and nephrectomized rats. At later time points, proteinuria for HSRA-UNX3 (82±22.9 mg/24h) and HSRA-UNX8 (46±18.1) were significantly higher than HSRA-C (11±6.4), while HSRA-S (109±15.7) demonstrated the highest proteinuria. GFR was lowest in HSRA-S (656±123.9 ul/min/gKW), followed by HSRA-UNX3 (1151±112.4), HSRA-UNX8 (1309±98.3) and HSRA-C (1544±111.7). Microarray studies have identified several developmental genes (Hox5b, Smoc2 and c-Kit) that may be linked to reduced nephron number and other structural changes that could predispose the HSRA-S to kidney injury later in life. These results demonstrate that rats born with a single kidney are more prone to renal injury than nephrectomized rats and the mechanism is likely different.
- © 2012 by American Heart Association, Inc.