Soft bone - hard arteries: a link?

Chronic kidney disease is characterized by mineral and various bone disorders associated with extraosseous and cardiovascular calcifications. Experimental studies and clinical observations in the general population and in chronic kidney disease patients show an inverse relationship between the extent of cardiovascular calcifications and bone mineral density or bone metabolic activity. Arterial calcification and osteoporosis are frequently observed in the same subjects and progress in parallel in postmenopausal women, and associations between histomorphometric indices of bone activity and vascular calcifications were also observed in patients with chronic and end-stage kidney diseases. The biological linkage between vascular calcifications and bone changes is certainly a part of the aging process, but in many studies these bone-vascular associations remained significant after adjustment for age, which suggests an age-independent causal relationship. Based on clinical and experimental evidence showing an association between bone disorders and functional and structural changes of the arterial system the concept of a bone-vascular axis was established complementary to the classical kidney-bone axis. Nevertheless, the factors or mechanisms accounting for these associations are not well understood, and could result from (1) arterial disease responsible for bone abnormalities; (2) action of common dysmetabolic or 'toxic' factors and mechanisms acting on bones and vessels, or (3) direct or indirect influence of bone cells and metabolism on the arterial system. This short review aims to illustrate these possible mechanisms.