Abstract
Calcium oxalate (CaOx) crystal formation, aggregation and growth is a common cause of kidney stone disease and nephrocalcinosis-related chronic kidney disease (CKD). Genetically modified mouse strains are frequently used as an experimental tool in this context but observed phenotypes may also relate to the genetic background or intestinal microbiota. We hypothesized that the genetic background or intestinal microbiota of mice determine CaOx crystal deposition and thus the outcome of nephrocalcinosis. Indeed, Casp1 -/-, Cybb -/- or Casp1 -/-/Cybb -/- knockout mice on a 129/C57BL/6J (B6J) background that were fed an oxalate-rich diet for 14 days did neither encounter intrarenal CaOx crystal deposits nor nephrocalcinosis-related CKD. To test our assumption, we fed C57BL/6N (B6N), 129, B6J and Balb/c mice an oxalate-rich diet for 14 days. Only B6N mice displayed CaOx crystal deposits and developed CKD associated with tubular injury, inflammation and interstitial fibrosis. Intrarenal mRNA expression profiling of 64 known nephrocalcinosis-related genes revealed that healthy B6N mice had lower mRNA levels of uromodulin (Umod) compared to the other three strains. Feeding an oxalate-rich diet caused an increase in uromodulin protein expression and CaOx crystal deposition in the kidney as well as in urinary uromodulin excretion in B6N mice but not 129, B6J and Balb/c mice. However, backcrossing 129 mice on a B6N background resulted in a gradual increase in CaOx crystal deposits from F2 to F7, of which all B6N/129 mice from the 7th generation developed CaOx-related nephropathy similar to B6N mice. Co-housing experiments tested for a putative role of the intestinal microbiota but B6N co-housed with 129 mice or B6N/129 (3rd and 6th generation) mice did not affect nephrocalcinosis. In summary, genetic background but not the intestinal microbiome account for strain-specific crystal formation and, the levels of uromodulin secretion may contribute to this phenomenon. Our results imply that only littermate controls of the identical genetic background strain are appropriate when performing knockout mouse studies in this context, while co-housing is optional.
Highlights
Calcium oxalate crystals is the main constituent of most kidney stones and account for approximately 75% of crystal-related kidney damage and eventually kidney failure [1]
We investigated whether the genetic background of mice affects Calcium oxalate (CaOx) crystal deposition in the kidneys and the outcomes of CaOx-related nephrocalcinosis in four different inbred mouse strains and whether co-housing for alignment of the intestinal microbiome might contribute to these physiological processes
We had hypothesized that the genetic background of mice and the intestinal microbiome after co-housing would affect CaOx crystal deposition in the kidneys and the outcomes of CaOx-related nephrocalcinosis in four common inbred mouse strains
Summary
Calcium oxalate crystals is the main constituent of most kidney stones and account for approximately 75% of crystal-related kidney damage and eventually kidney failure [1]. Hyperoxaluriarelated CaOx stones form when the urine becomes excessively supersaturated due to the intake of oxalate-rich food, leading to crystal formation, growth, aggregation and retention in the renal tubular lumen [2] This process is independent of urinary pH [3] but affected by the composition of minerals or proteins, such as calcium, phosphate, magnesium, citrate, uromodulin, nephrocalcin, osteopontin, calgranulin and macroglobulin [4]. Risk factors, such as oxalate-rich diet, obesity, diabetes, hypertension and metabolic syndrome, have been linked to contribute to CaOx stone formation [5]. A better understanding of the mechanisms involved in CaOx stones formation to predict and facilitate the development of more-effective drugs are of great need for preventing and treating this disease
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
