What causes arterial calcification?

What Causes Arterial Calcification

Arterial calcification is a complex, actively regulated process driven by multiple mechanisms including disturbed mineral metabolism (particularly hyperphosphatemia in CKD), inflammation, atherosclerosis, aging, diabetes, and deficiency of protective calcification inhibitors—not simply a passive degenerative process. 1

Primary Pathophysiological Mechanisms

Disturbed Mineral Metabolism

• Hyperphosphatemia plays a central role in driving arterial calcification, particularly in patients with chronic kidney disease (CKD), where it acts as a key driver of CKD-associated cardiovascular disease 1
• Mineral and bone disorders, including secondary hyperparathyroidism, are closely associated with coronary artery calcification development, especially early after CKD onset 1
• The pathophysiology is not directly correlated with serum calcium and phosphate levels alone, indicating more complex regulatory mechanisms 1

Active Cellular Processes

• Dysfunctional vascular smooth muscle cells are central players in the calcification process, undergoing osteochondral differentiation rather than simply accumulating passive calcium deposits 2
• Macrophages, mast cells, and smooth muscle cells are the primary cells implicated in driving arterial calcification 3
• Microvesicles released from these cells contribute to the active mineralization process 2

Regulatory Protein Imbalance

• Arterial calcification results from complex interplay between stimulating proteins (bone morphogenetic protein-2 [BMP-2], RANKL) and inhibitory proteins (matrix Gla protein [MGP], BMP-7, osteoprotegerin, fetuin-A, osteopontin) 4
• Deficiency of protective calcification inhibitors is a major etiological factor 1
• MGP requires vitamin K-dependent gamma-carboxylation to function; vitamin K deficiency, vitamin K antagonists (like warfarin), and oxidative stress prevent MGP activation, allowing BMP-2 to induce mineralization 3

Two Distinct Anatomical Patterns

Intimal Calcification

• Associated with atherosclerosis and occurs in the vessel intima 2
• Driven by traditional cardiovascular risk factors including age, diabetes, inflammation, and atherosclerotic processes 1
• Represents calcified atherosclerotic plaques 1

Medial Arterial Calcification (MAC)

• Occurs in the vessel media and is associated with arterial stiffening 2
• Aging and cellular senescence play pivotal roles in MAC development 1
• More closely related to diabetes and hypertension than to traditional atherosclerotic risk factors 1
• CKD accelerates the aging process and increases MAC risk 1

Disease-Specific Mechanisms

Chronic Kidney Disease

• Significantly more pronounced, disseminated, and fast-progressing calcification occurs in CKD patients compared to the general population 1
• Inflammation and obesity, commonly seen in CKD, accelerate atherosclerotic plaque formation 1
• Elevated FGF23 levels may be significantly involved in arterial calcification and subsequent left ventricular hypertrophy 1
• Uremic toxins contribute to the calcification process 1

Diabetes Mellitus

• Hyperglycemia and metabolic derangements accelerate arterial calcification 1
• Diabetes is associated with both intimal and medial calcification patterns 1
• Oxidative stress in diabetics causes endothelial injury that may trigger calcification as an immune response 5

Contributing Risk Factors

Traditional Cardiovascular Risk Factors

• Age is a paramount risk factor across all populations 1
• Hypertension contributes through endothelial injury and arterial wall stress 1, 2
• Hyperlipidemia and smoking promote atherosclerotic calcification 1
• Male sex is associated with higher calcification rates 1

Inflammation and Oxidative Stress

• Chronic inflammation accelerates both atherosclerotic and medial calcification 1
• Oxidative stress causes endothelial injury that may trigger calcification 5
• Inflammatory cells and cytokines promote osteogenic differentiation of vascular smooth muscle cells 4

Genetic and Molecular Factors

• Monogenic deficiencies in ENPP1, CD73, and ABCC6 drive premature arterial calcification syndromes (GACI, PXE, and ACDC) 6
• These genes function as critical components in larger networks that balance calcification promotion and suppression 6
• Genetic factors identified through genome-wide association studies contribute to calcification susceptibility 6

Important Clinical Considerations

Common Pitfalls

• Do not assume calcification is simply passive calcium deposition—it is an active, regulated biological process requiring cellular transformation 2
• Current imaging techniques cannot differentiate between intimal atherosclerotic calcification and medial calcification, yet this distinction may be clinically significant 1
• Lipid-lowering therapy may paradoxically worsen calcification progression despite reducing cardiovascular events 5

Emerging Perspective

• Calcification may develop as an immune response to endothelial injury (from shear stress, oxidative stress, or other insults) rather than purely as pathological progression 5
• This hypothesis explains why calcification can be protective against plaque rupture and why it is unresponsive to lipid-lowering agents 5
• The focus should shift toward preventing and treating causes of endothelial injury rather than attempting to reverse established calcification 5