Generation and characterization of a novel rat model of primary hyperoxaluria type 1 with a nonsense mutation in alanine-glyoxylate aminotransferase gene

Abstract

Primary hyperoxaluria type 1 (PH1) is a severe inherited disorder caused by a genetic defect in alanine-glyoxylate aminotransferase (AGXT), which results in recurrent urolithiasis and renal failure. Animal models that precisely reflect human PH1 phenotypes are lacking. We aimed to develop a novel PH1 rat model and study the mechanisms involved in PH1 deterioration. One cell stage Sprague-Dawley embryos were injected with the CRISPR/Cas9 system to introduce a Q84X mutation in Agxt. Liver tissues were harvested to determine Agxt expression. Urine oxalate, crystals, and electrolyte levels in Agxt^Q84X and wild-type (WT) littermates were evaluated. Kidney tissues were used for Pizzolato staining and kidney injury evaluation. Data showed that Agxt mRNA and protein were absent in Agxt^Q84X rats. At 4 and 24 wk, Agxt^Q84X rats displayed 2.1- and 2.9-fold higher urinary oxalate levels, respectively, compared with WT littermates. As a result, calcium oxalate (CaOx) crystals in urine were revealed in all Agxt^Q84X rats but in none of the WT rats. We also observed bladder stones in 36.4% of Agxt^Q84X rats, of which 44.4% had renal CaOx deposition. Moreover, the elevated serum urea and creatinine levels indicated the impaired renal function in Agxt^Q84X rats. Further investigation revealed significantly increased expression of inflammation-, necroptosis-, and fibrosis-related genes in the kidneys of Agxt^Q84X rats with spontaneous renal CaOx deposition, indicating that these pathways are involved in PH1 deterioration. Collectively, these results suggest that this rat model has broad applicability in mechanistic studies and innovative therapeutics development for PH1 and other kidney stone diseases.NEW & NOTEWORTHY Primary hyperoxaluria type 1 is a severe inherited disorder that results in recurrent urolithiasis and renal failure. We generated an alanine-glyoxylate aminotransferase (Agxt)^Q84X nonsense mutant rat model that displayed an early onset of hyperoxaluria, spontaneous renal CaOx precipitation, bladder stone, and kidney injuries. Our results suggest an interaction of renal CaOx crystals with the activation of inflammation-, fibrosis-, and necroptosis-related pathways. In all, the Agxt^Q84X rat strain has broad applicability in mechanistic studies and the development of innovative therapeutics.

Keywords: CRISPR/Cas9; calcium oxalate; hyperoxaluria; inflammation; necroptosis.