[Origin of the mediacalcosis in kidney failure]

Extrarenal calcifications, particularly affecting the cardiovascular system, are common observations which can be a source of serious complications in patients with chronic renal disease, especially those on dialysis. In these patients, cardiovascular disease - myocardial infarction, arrhythmia, calcified valvulopathy, stroke, peripheral ischemic arteriopathy, calciphylaxy, etc. - is the leading cause of death (more than 50%). These complications are closely related to the presence of vascular calcifications (VC) which are much more frequent, severe, and progressive than in the general population. Previously, these calcifications were considered to arise via a passive process within the context of comorbid conditions without specific signs of gravity: high blood pressure, atherosclerosis, aging, diabetes, smoking, dyslipidemia, chronic micro-inflammation, hyperhomocysteinemia, disorders of calcium-phosphorus metabolism. It is now established that VC arise via a complex, probably regulated, active process analogous to the processes leading to bone formation and/or remodeling. New insight provided by a large body of work designed to ascertain the mechanisms underlying the onset of VC has enabled the development of new diagnostic and therapeutic approaches. It is now possible to identify factors clearly favoring the formation of VC: TNF-alpha (which stimulates cell necrosis/apoptosis), CRP, oxidized lipids, AGEs, leptin, inorganic phosphate, high calcium-phosphorus product (CaxPO(4)), calcium, 1,25-OH(2)D(3) and Vitamin D(3), PTHrP (via an intracrine pathway), cyclic AMP, TGF-beta, bone morphogenic protein 2 (BMP2) and factors protective against the formation of VC: magnesium, HDL, inorganic pyrophosphate, albumin, ahsg/fetuin A, osteopontin (OPN), osteoprotegerin (OPG), osteonectin (ON), bone morphogenic protein 7 (BMP7), klotho, PTHrP (via a paracrine pathway), matrix gla protein (MGP), PTH (via Msx2) and vitamin K. In conclusion, until recently, neglected disorders of calcium-phosphorus metabolism are currently recognized as the main actors in the process leading to vascular mediacalcosis in patients with chronic kidney failure.