Mechanisms and treatment of extraosseous calcification in chronic kidney disease

Strong and unidirectional associations exist between the severity of cardiovascular calcifications and mortality in patients with advanced chronic kidney disease. In the past 10 years, a wealth of experimental and clinical information has been published on the key pathophysiological events that contribute to the development and progression of vascular and soft-tissue calcifications. These processes involve a sensitive balance of calcification inhibition, induction and removal. The traditional view of regarding secondary hyperparathyroidism and elevated calcium x phosphate product as the pivotal risk factors for calcification has been challenged by data demonstrating a role for other, more subtle and complex pathomechanisms. These mechanisms include the loss of endogenous calcification inhibitors, deficient clearance of calcified debris, effects of vitamin K and vitamin D, and the action of calcification inducers as in osteogenic transdifferentiation. In this Review, we describe our current knowledge of the factors involved in the passive and active regulation of extraosseous calcification processes, with an assessment of their importance as targets for future diagnostic and therapeutic interventions.