Vitamin D metabolites regulate matrix vesicle metalloproteinase content in a cell maturation-dependent manner

Matrix vesicles are extracellular organelles produced by cells that mineralize their matrix. They contain enzymes that are associated with calcification and are regulated by vitamin D metabolites in a cell maturation-dependent manner. Matrix vesicles also contain metalloproteinases that degrade proteoglycans, macromolecules known to inhibit calcification in vitro, as well as plasminogen activator, a proteinase postulated to play a role in activation of latent TGF-β. In the present study, we examined whether matrix vesicle metalloproteinase and plasminogen activator are regulated by 1,25(OH) ₂D ₃ and 24,25 (OH) ₂D ₃. Matrix vesicles and plasma membranes were isolated from fourth passage cultures of resting zone chondrocytes that bad been incubated with 10 ^-1010 ^-7 M24 25(OH) ₂D ₃ or growth zone chondrocytes incubated with 10 ^-11-10 ^-8 M 1,25(OH) ₂D ₃, and their alkaline phosphatase, active and total neutral metalloproteinase, and plasminogen activator activities determined. 24,25(OH) ₂D ₃ increased alkaline phosphatase by 35-60%, decreased active and total metalloproteinase by 75%, and increased plasminogen activator by fivefold in matrix vesicles from resting zone chondrocyte cultures. No effect of vitamin D treatment was observed in plasma membranes isolated from these cultures. In contrast, 1,25(OH) ₂D ₃ increased alkaline phosphatase by 35-60%, but increased active and total metalloproteinase three- to fivefold and decreased plasminogen activator by as much as 75% in matrix vesicles isolated from growth zone chondrocyte cultures. Vitamin D treatment bad no effect on plasma membrane alkaline phosphatase or metalloproteinase, but decreased plasminogen activator activity. The results demonstrate that neutral metalloproteinase and plasminogen activator activity in matrix vesicles are regulated by vitamin D metabolites in a cell maturation-specific manner. In addition, they support the hypothesis that 1,25(OH) ₂D ₃ regulation of matrix vesicle function facilitates calcification by increasing alkaline phosphatase and phospholipase A ₂ specific activities as well as metalloproteinases which degrade proteoglycans.