Dean D D, Boyan B D, Muniz O E, Howell D S, Schwartz Z
Department of Orthopaedics, University of Texas Health Texas Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78284-7774, USA.
Calcif Tissue Int. 1996 Aug;59(2):109-16. doi: 10.1007/s002239900096.
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-beta. In the present study, we examined whether matrix vesicle metalloproteinase and plasminogen activator are regulated by 1, 25(OH)2D3 and 24,25(OH)2D3. Matrix vesicles and plasma membranes were isolated from fourth passage cultures of resting zone chondrocytes that had been incubated with 10(-10)-10(-7) M24, 25(OH)2D3 or growth zone chondrocytes incubated with 10(-11)-10(-8) M 1,25(OH)2D3, and their alkaline phosphatase, active and total neutral metalloproteinase, and plasminogen activator activities determined. 24,25(OH)2D3 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)2D3 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 had 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)2D3 regulation of matrix vesicle function facilitates calcification by increasing alkaline phosphatase and phospholipase A2 specific activities as well as metalloproteinases which degrade proteoglycans.
基质小泡是由使细胞外基质矿化的细胞产生的细胞外细胞器。它们含有与钙化相关的酶，并以细胞成熟依赖的方式受维生素D代谢物调节。基质小泡还含有金属蛋白酶，可降解蛋白聚糖（一种已知在体外抑制钙化的大分子），以及纤溶酶原激活剂（一种推测在潜伏性转化生长因子-β激活中起作用的蛋白酶）。在本研究中，我们检测了基质小泡金属蛋白酶和纤溶酶原激活剂是否受1,25(OH)₂D₃和24,25(OH)₂D₃调节。从用10⁻¹⁰ - 10⁻⁷ M 24,25(OH)₂D₃孵育的静止区软骨细胞的第四代培养物中分离出基质小泡和质膜，或者从用10⁻¹¹ - 10⁻⁸ M 1,25(OH)₂D₃孵育的生长区软骨细胞中分离出基质小泡和质膜，并测定它们的碱性磷酸酶、活性和总中性金属蛋白酶以及纤溶酶原激活剂活性。24,25(OH)₂D₃使静止区软骨细胞培养物的基质小泡中的碱性磷酸酶增加35 - 60%，使活性和总金属蛋白酶降低75%，并使纤溶酶原激活剂增加五倍。在从这些培养物中分离出的质膜中未观察到维生素D处理的影响。相反，1,25(OH)₂D₃使生长区软骨细胞培养物分离出的基质小泡中的碱性磷酸酶增加35 - 60%，但使活性和总金属蛋白酶增加三到五倍，并使纤溶酶原激活剂降低多达75%。维生素D处理对质膜碱性磷酸酶或金属蛋白酶没有影响，但降低了纤溶酶原激活剂活性。结果表明，基质小泡中的中性金属蛋白酶和纤溶酶原激活剂活性以细胞成熟特异性方式受维生素D代谢物调节。此外，它们支持这样的假说，即1,25(OH)₂D₃对基质小泡功能的调节通过增加碱性磷酸酶和磷脂酶A₂的比活性以及降解蛋白聚糖的金属蛋白酶来促进钙化。
