Microvasculopathy and soft tissue calcification in mice are governed by fetuin-A, magnesium and pyrophosphate

Abstract

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 targets that could be influenced by dietary of parenteral supplementation. 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 parenteral administration of fetuin-A dietary magnesium supplementation, phosphate restriction, or by or parenteral pyrophosphate. All treatments markedly reduced soft tissue calcification, demonstrated by computed tomography, histology and tissue calcium measurement. 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, magnesium, and pyrophosphate. 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, magnesium and pyrophosphate levels.

Chronic Kidney Disease-Induced Arterial Media Calcification in Rats Prevented by Tissue Non-Specific Alkaline Phosphatase Substrate Supplementation Rather Than Inhibition of the Enzyme

“…In line with other studies using different animal models to target the PPi/Pi ratio by either TNAP inhibition or PPi supplementation, we found no differences in circulating PPi levels between the different study groups [ 19 , 32 , 49 , 50 ]. It is worth noting that the PPi plasma values reflect the whole-body PPi metabolism.…”

Lumenal calcification and microvasculopathy in fetuin-A-deficient mice lead to multiple organ morbidity

“…D2,Ahsg-/-mice are certainly one of the most calcification-susceptible mouse strains known [29]. Concurrent 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 at once affecting three potent extracellular regulators of mineralization [30]. Unsurprisingly, this prominent calcification phenotype is associated with bone abnormalities [31], decreased breeding performance, organ damage, and increased mortality.…”

“…The full penetrance and severe expression of the calcification phenotype renders D2,Ahsg-/-mice ideal for studying mechanisms and therapeutic approaches for calcification 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 calcification in these mice.…”

Calciprotein Particles

“… 46 Exogenous fetuin-A supplementation inhibits the development of calcified thrombi in fetuin-A–deficient mice, confirming its relevance to vasculopathy. 44 Expectedly, serum Ca 2+ , PO 4 3 − , low fetuin-A, and high CPP levels all associate with the development of vascular pathology. 47 – 49 …”

“…MGP- and GRP-deficient mice develop medial arterial calcifications 34 , 42 , 43 and may prematurely die from blood vessel rupture. 34 Fetuin-A–deficient mice develop numerous calcified thrombi in the microvasculature 44 , 45 and intimal arterial calcifications on atherosclerosis-prone genetic backgrounds. 46 Exogenous fetuin-A supplementation inhibits the development of calcified thrombi in fetuin-A–deficient mice, confirming its relevance to vasculopathy.…”