Microvasculopathy And Soft Tissue Calcification In Mice Are Governed by Fetuin-A, Pyrophosphate And Magnesium

Abstract

Objective -Calcifications can disrupt organ function in the cardiovascular system and the kidney, and are particularly common in patients with chronic kidney disease (CKD). Fetuin-A deficient mice maintained against the genetic background DBA/2 exhibit particularly severe soft tissue calcifications, while fetuin-A deficient C57BL/6 mice remain healthy. We employed molecular genetic analysis to identify risk factors of calcification in fetuin-A deficient mice. We sought to identify pharmaceutical therapeutic target that could be influenced by dietary of parenteral supplementation.Approach and Results -We studied the progeny of an intercross of fetuin-A deficient DBA/2 and C57BL/6 mice to identify candidate risk genes involved in calcification. We determined that a hypomorphic mutation of the Abcc6 gene, a liver ATP transporter supplying systemic pyrophosphate, and failure to regulate the TRPM6 magnesium transporter in kidney were associated with severity of calcification. Calcification prone fetuin-A deficient mice were alternatively treated with dietary phosphate restriction, magnesium supplementation, or by parenteral administration of fetuin-A or pyrophosphate. All treatments markedly reduced soft tissue calcification, demonstrated by computed tomography, histology and tissue calcium measurement.Conclusions -We show that pathological ectopic calcification in fetuin-A deficient DBA/2 mice is caused by a compound deficiency of three major extracellular and systemic inhibitors of calcification, namely fetuin-A, pyrophosphate, and magnesium. All three of these are individually known to contribute to stabilize protein-mineral complexes and thus inhibit mineral precipitation from extracellular fluid. We show for the first time a compound triple deficiency that can be treated by simple dietary or parenteral supplementation. This is of special importance in patients with advanced CKD, who commonly exhibit reduced serum fetuin-A, pyrophosphate and magnesium levels.

Microvasculopathy, Luminal Calcification and Premature Aging in Fetuin-A Deficient Mice

“…D2,Ahsg-/-mice are certainly one of the most calcification-susceptible mouse strains known [29]. Concurrently with this work we established that the calcification phenotype of D2,Ahsg-/-mice is governed by combined deficiency of fetuin-A, pyrophosphate and magnesium, thus affecting three potent extracellular regulators of mineralization at once [30]. This prominent calcification phenotype is not surprisingly associated with bone abnormalities [31], decreased breeding performance, organ damage, and increased mortality.…”

“…The full penetrance and severe expression of the calcification phenotype renders these mice ideal for studying mechanisms and therapeutic approaches for mineralization diseases. A concurrent study from our laboratory has shown that the severe soft tissue calcification in the mice is governed by fetuin-A, pyrophosphate and magnesium, and can in fact be prevented by prophylactic supplementation of each one of these major systemic inhibitors of calcification [30].The aim of this present study was to analyze the early events leading to soft tissue mineralization in these mice. We first used computed tomography to survey and identify organs affected by ectopic mineralization in living mice.…”