Inhibition of RET signaling attenuates renal hypertrophic growth, proximal tubule dilation, and kidney damage in the 5/6Nx rat model of chronic kidney disease

Abstract

Progression of chronic kidney disease (CKD) involves compensatory hypertrophy of remaining nephrons leading to additional nephron loss. Understanding the precise mechanisms responsible for hypertrophy may help develop novel strategies to preserve renal function in people living with CKD. Our laboratory utilized the 5/6 nephrectomy (5/6Nx) rat model of renal insufficiency, where 2/3 of the left kidney and the entire right kidney was surgically excised in 10-week-old male Sprague Dawley rats. The remnant kidney underwent substantial compensatory hypertrophy between 5- and 7-weeks post-surgery. We then performed transcriptomic analysis of kidneys collected 6 weeks after 5/6Nx or sham surgery (n=6/group) to gain an unbiased perspective of molecular pathways involved with hypertrophic remodeling. Through transcriptomic analysis, we found that transcript expression of glial cell derived Neurotrophic factor (GDNF) was 7.64-fold higher in 5/6Nx remnant kidneys compared to sham-operated control. GDNF is an essential kidney morphogen in the developmental process that had not been implicated in renal compensatory hypertrophic remodeling. Immunohistochemistry (IHC) showed increased GDNF protein expression in the 5/6Nx remnant kidney. In the kidney GDNF elicits biological function through binding of its co-receptor GDNF family receptor α (GFRα) which then forms a complex with the tyrosine kinase RET resulting in downstream signaling. We hypothesized that GDNF signaling promotes tubular hypertrophic growth response in the 5/6Nx. To test this, we pharmacologically inhibited the GDNF/GFRα/RET complex using pralsetinib (3mg/kg/bw in corn oil; 1x daily oral gavage) from 5- to 7-weeks post-5/6Nx or sham surgery. Treatment control animals received vehicle. During this time we collected blood, urine, and conducted ultrasound analysis of the remnant kidney transverse cross sectional-area. Analysis of left kidney CSA revealed a decrease in kidney size between weeks 5 and 7 (1.58 ± 0.89 cm2, treatment vs 2.06 ± 0.071 cm2, vehicle; p=0.02; a two-way RM ANOVA), kidney wet weight and kidney/body weight were lower in pralsetinib vs. vehicle treated animals (66.85 ± 4.47% and 67.19 ± 2.30%, respectively; mean ± SEM, p < 0.05, student’s t-test). IHC analysis of renal cortex showed pralestinib treatment decreased proximal tubule diameter compared to vehicle (61.51 ± 3.45 μm, treatment vs 71.33 ± 9.82 μm, vehicle; p=0.01, student’s t-test). Additionally, plasma creatinine and blood urea nitrogen levels were decreased when compared to vehicle treated animals (0.88 ± 0.51 mg/dL, treatment vs 1.4 ± 0.21 mg/dL, vehicle; mean ± SEM, p < 0.03, student’s t-test and 37.63 ± 10.62 mg/dL, treatment vs 71.13 ± 33.50 mg/dL, vehicle; mean ±SEM, p<0.001, student’s t-test, respectively). Taken together, our data suggests inhibition of RET signaling prevented whole kidney hypertrophic growth and proximal tubule remodeling while preserving kidney function following 5/6Nx in rats. NIH-T32 Training Grant This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.