Cartilage is a group of tissues produced by chondrocytes that is characterized by a relative lack of vascularity and consists of cells surrounded by a specialized extracellular matrix composed predominantly of type II collagen and proteoglycan, often in the form of proteoglycan aggregate. This chapter explains that cartilage, much like other tissues, is a family of tissues spanning a broad spectrum of cell maturation states. In growth plate, a subset of the cartilage phenotype, chondrocytes can be seen at distinct states of maturation in a linear array. Using a variety of in vivo and in vitro assays, investigators have been able to show that the growth plate is sensitive to vitamin D regulation, with 24R,25(OH)2D3 affecting less mature cells, particularly those of the resting zone, and 1α,25(OH)2D3 modulating activities in the growth zone (prehypertrophic and upper hypertrophic) cartilage. Rapid cell-membrane-mediated events via Pdia3 and vitamin D receptor (VDR) may result in secondary genomic responses via protein phosphorylation cascades and MAP kinase; in matrix vesicles, rapid membrane effects may be termed nongenomic because no gene expression or protein synthesis is possible. 1α,25(OH)2D3 and 24R,25(OH)2D3 regulate chondrocyte proliferation, metabolism, differentiation, and maturation, as well as events in the extracellular matrix. The effects are cell maturation-dependent and organelle-specific, and may involve both VDR-dependent and VDR-independent genomic as well as nongenomic mechanisms.
|Original language||English (US)|
|Title of host publication||Vitamin D|
|Number of pages||13|
|State||Published - 2011|
ASJC Scopus subject areas