Deficiency in Pappa2 expression reduces nephron endowment and associates with hypertension and chronic kidney disease in rats

Abstract

IntroductionRecently, a congenic Dahl salt‐sensitive (SS) 26‐P rat strain containing Pappa2 allele of salt‐insensitive Brown Norway (BN) rat strain was identified which found to exhibit significant protection from salt‐induced hypertension and kidney injury. Pappa2 (pregnancy associated plasma protein A2) was found to be differentially expressed in the kidney and altered by dietary salt intake. Pappa2 is a metalloproteinase which releases IGF by cleaving IGFBP5 and has been found to play an important role in the development of bone size and angiogenesis. It has not been previously been implicated to play a role in kidney development nor contribute to cardiovascular function and hypertension. The present study determined whether Pappa2 contributes to kidney development, particularly nephron number and the relationship of these findings with hypertension and chronic kidney disease in rats.MethodsThe localization of Pappa2 in embryonic E20.5 and postnatal P0 kidneys of SS and 26‐P was determined by immunohistochemistry. CRISPR/Cas9 was used to knockout the Pappa2 gene in 26‐P strain. Acid‐maceration method was used to determine glomeruli per kidney at P50 of Pappa2‐WT and Pappa2‐KO rats. Pappa2‐WT and Pappa2‐KO rats (male; 9 wk age) were implanted with arterial catheters and radiotransmitters to record mean arterial pressure (MAP; 24/d). Urine was collected to assess micro‐albumin excretion rate, as an index of renal injury.ResultsImmunohistochemistry studies found that Pappa2 was localized in the ureteric bud at E20.5 kidneys of 26‐P embryos suggesting that Pappa2 could be important for ureteric branching and nephron endowment. CRISPR‐Cas9 mutation of Pappa2 in the 26‐P rat resulted in a severe deficit in the number of mature nephrons in rats at day 50 (26833 ± 892 glomeruli/kidney in Pappa2‐KO vs 36508 ± 1276 glomeruli/kidney in Pappa2‐WT). MAP of 10 weeks Pappa2‐KO rats which were maintained on a 0.4% NaCl diet since weaning averaged 121 ± 2.3 mmHg compared with Pappa2‐WT rat which averaged 113 ± 1.3 mmHg (P<0.05). Albumin excretion rates (UalbV) averaged 151 ± 42 and 51 ± 26 mg/day in 6 month old Pappa2‐KO and Pappa2‐WT rats fed a 0.4% NaCl diet respectively, and progressively increased to 270 ± 85 and 97 ± 28 mg/day at 9 months of age.ConclusionPappa2 determines nephron number which is closely associated with hypertension and kidney injury in rats.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.