MINERAL ION-INDUCED RELEASE OF MINERALIZATION-COMPETENT MATRIX VESICLES FROM HUMAN VASCULAR SMOOTH MUSCLE CELLS

Vitamin D in Vascular Calcification: A Double-Edged Sword?

Vascular calcification (VC) as a manifestation of perturbed mineral balance, is associated with aging, diabetes and kidney dysfunction, as well as poorer patient outcomes. Due to the current limited understanding of the pathophysiology of vascular calcification, the development of effective preventative and therapeutic strategies remains a significant clinical challenge. Recent evidence suggests that traditional risk factors for cardiovascular disease, such as left ventricular hypertrophy and dyslipidaemia, fail to account for clinical observations of vascular calcification. Therefore, more complex underlying processes involving physiochemical changes to mineral balance, vascular remodelling and perturbed hormonal responses such as parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF-23) are likely to contribute to VC. In particular, VC resulting from modifications to calcium, phosphate and vitamin D homeostasis has been recently elucidated. Notably, deregulation of vitamin D metabolism, dietary calcium intake and renal mineral handling are associated with imbalances in systemic calcium and phosphate levels and endothelial cell dysfunction, which can modulate both bone and soft tissue calcification. This review addresses the current understanding of VC pathophysiology, with a focus on the pathogenic role of vitamin D that has provided new insights into the mechanisms of VC.

Novel insights into vascular calcification

Vascular calcification is not just a hallmark of uremic arterio- and atherosclerosis, but also a significant cardiovascular risk factor in patients with chronic kidney disease. In contrast to the previous assumption that vascular calcification predominantly occurs by passive precipitation of calcium and phosphate ions, recent research led to the insight that extraosseous calcification is a highly regulated process. High serum phosphate and calcium levels may induce a process of osteogenic 'bone-like' differentiation of vascular smooth muscle cells, while deficiencies of calcification inhibitors or a disturbed balance towards calcification inducers may have a relevant pathophysiological influence on the initiation and progression of calcified lesions. This overview summarizes some of the best explored novel risk factors for disturbances of calcium and phosphate homeostasis and points to the integral role of hyperphosphatemia as a modifiable key trigger in calcification processes.