Chronic mineral dysregulation promotes vascular smooth muscle cell adaptation and extracellular matrix calcification.
In chronic kidney disease (CKD) vascular calcification occurs in response to deranged calcium and phosphate metabolism and is characterized by vascular smooth muscle cell (VSMC) damage and attrition. To gain mechanistic insights into how calcium and phosphate mediate calcification, we used an ex vivo model of human vessel culture. Vessel rings from healthy control subjects did not accumulate calcium with long-term exposure to elevated calcium and/or phosphate. In contrast, vessel rings from patients with CKD accumulated calcium; calcium induced calcification more potently than phosphate (at equivalent calcium-phosphate product). Elevated phosphate increased alkaline phosphatase activity in CKD vessels, but inhibition of alkaline phosphatase with levamisole did not block calcification. Instead, calcification in CKD vessels most strongly associated with VSMC death resulting from calcium- and phosphate-induced apoptosis; treatment with a pan-caspase inhibitor ZVAD ameliorated calcification. Calcification in CKD vessels was also associated with increased deposition of VSMC-derived vesicles. Electron microscopy confirmed increased deposition of vesicles containing crystalline calcium and phosphate in the extracellular matrix of dialysis vessel rings. In contrast, vesicle deposition and calcification did not occur in normal vessel rings, but we observed extensive intracellular mitochondrial damage. Taken together, these data provide evidence that VSMCs undergo adaptive changes, including vesicle release, in response to dysregulated mineral metabolism. These adaptations may initially promote survival but ultimately culminate in VSMC apoptosis and overt calcification, especially with continued exposure to elevated calcium.
Shroff
Rukshana C
RC
Great Ormond Street Hospital and University College London Institute of Child Health, London, UK.
McNair
Rosamund
R
Skepper
Jeremy N
JN
Figg
Nichola
N
Schurgers
Leon J
LJ
Deanfield
John
J
Rees
Lesley
L
Shanahan
Catherine M
CM
D000222:Adaptation, Physiological / Q000502:physiology*; D000293:Adolescent; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D002114:Calcinosis / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D002908:Chronic Disease; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism*; D006801:Humans; D007223:Infant; D007674:Kidney Diseases / Q000378:metabolism* / Q000628:therapy; D007978:Levamisole / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D006435:Renal Dialysis; D046509:Tissue Culture Techniques
D050659:Core Binding Factor Alpha 1 Subunit; D010710:Phosphates; C493709:RUNX2 protein, human; D007978:Levamisole; D000469:Alkaline Phosphatase; D002118:Calcium