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

Abstract

Objective -The plasma protein fetuin-A mediates the formation of protein-mineral colloids known as calciprotein particles (CPP) -rapid clearance of these CPP by the reticuloendothelial system prevents errant mineral precipitation and therefore ectopic mineralization (calcification). The mutant mouse strain D2,Ahsg-/-combines fetuin-A deficiency with the mineralization-prone DBA/2 genetic background, having a particularly severe compound phenotype of microvascular and soft tissue mineralization. Here we studied mechanisms leading to soft tissue mineralization, organ damage and premature aging in these mice.Approach and Results -We analyzed mice longitudinally by echocardiography, X-raycomputed tomography, analytical electron microscopy, histology, mass spectrometry proteomics, and genome-wide microarray-based expression analyses of D2 wildtype and Ahsg-/-mice.Fetuin-A deficient mice had calcified lesions in myocardium, lung, brown adipose tissue, reproductive organs, spleen, pancreas, kidney and the skin, associated with reduced growth, cardiac output and premature aging. Importantly, early stage calcified lesions presented in the lumen of the microvasculature suggesting precipitation of mineral containing complexes from the fluid phase of blood. Genome-wide expression analysis of calcified lesions and surrounding (not calcified) tissue, together with morphological observations, indicated that the ectopic mineralization was not associated with osteochondrogenic cell differentiation, but rather with thrombosis and fibrosis.Conclusions -Collectively, these results demonstrate that pathological mineralization can start by intravascular mineral deposition causing microvasculopathy, which impacts on growth, organ function and survival. Our study underscores the importance of fetuin-A and related systemic regulators of mineralized matrix metabolism to prevent cardiovascular disease, especially in dysregulated mineral homeostasis.

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

“…We showed that dietary magnesium, low dietary phosphate, parenteral fetuin-A and pyrophosphate supplementation all prevented the formation of calcified lesions in fetuin-A deficient DBA/2 mice suggesting that similar therapeutic approaches might also reduce early stage CKD-associated cardiovascular calcifications and in calciphylaxis. Notably, these calcifications occurred without any signs of osteogenic conversion of calcifying cells, stressing the importance of extracellular mineral balance to prevent unwanted mineralization [21].…”

“…Recently, we showed that ectopic calcification in DBA/2 fetuin-A deficient mice starts in the microvasculature and is associated with premature ageing and cardiac failure, and that cellular osteogenesis was not involved [21].Thus, we concentrated on major extracellular regulators of calcification. Figure 1f,g show that serum calcium (Ca) and phosphate (Pi), major ionic drivers of calcification, were similar in DBA/2 and C57BL/6 wt and fetuin-A deficient mice.…”

“…In addition, severe renal calcinosis causes CKD and secondary hyperparathyroidism [17]. Ultimately in these mice, myocardial calcification is associated with fibrosis, diastolic dysfunction and increased mortality [20,21]. In contrast fetuin-A deficient mice maintained against the genetic background C57BL/6 do not calcify spontaneously.…”

Reduction of Calciprotein Particles in Adults Receiving Infliximab for Chronic Inflammatory Disease

“…(17) In vitro studies have shown that CPP can induce vascular smooth muscle cell calcification and expression of inflammatory mediators, (18,19) whilst inhibiting osteoblast mineralisation. (20) Animal models have shown that circulating CPP cause vascular luminal (21) and endothelial (22) lesions. Taken together, it is proposed that elevated levels of CPP may not be just a marker of disordered homeostatic mechanisms, but may themselves be mediators of vascular and bone pathology.…”