Relationship between vitamin D receptor gene (VDR) polymorphisms, vitamin D status, osteoarthritis and intervertebral disc degeneration

The vitamin D endocrine system is involved in bony and cartilaginous metabolisms and alterations in the homeostasis of this system could be associated to pathological conditions of cartilaginous tissue. In this context, the presence of polymorphisms in the vitamin D receptor gene (VDR), in association with the susceptibility to common osteochondral diseases, was largely investigated. The aim of this review was to summarize data present in literature, analyzing the association of the VDR polymorphisms, vitamin D status and knee cartilage and intervertebral disc pathologies, trying to suggest links between the different specific pathologies analyzed. Concerning the association between VDR polymorphisms and cartilaginous tissue diseases, we found controversial reports. However, the great majority of papers reported an association with lumbar disc degeneration, whereas about half of the studies found an association with osteoarthritis. A further association between VDR polymorphisms (in linkage disequilibrium) and the presence of specific characteristics of these diseases, in particular the formation of osteophytes, was evidenced. Finally, the influence of vitamin D status on these pathologies was evaluated, trying to evidence the relation between the presence of particular genetic variants in the VDR and vitamin D levels or to show whether a particular vitamin D status could predispose to the development or progression of such diseases, however, no significant associations were found. In the future, given the role of vitamin D system in the cartilaginous tissue metabolism, it could be interesting to perform functional and tissue specific studies to analyze the interplay between the different VDR variants and its ligand.