Determinants of extracellular matrix mineralization

细胞外基质矿化的决定因素

• 批准号: 6786527
• 负责人: Gerard Karsenty
• 金额: $ 24.39万
• 依托单位: UNIVERSITY OF TX MD ANDERSON CAN CTR
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2005-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6786527
• 关键词: alkaline phosphatase; calcium ion; cartilage development; cell differentiation; chondrocytes; developmental genetics; extracellular matrix; extracellular matrix proteins; gene expression; gene interaction; gene targeting; genetic regulation; genetic transcription; genetically modified animals; immunocytochemistry; in situ hybridization; laboratory mouse; molecular cloning; normal ossification; northern blottings; osteoblasts; pathologic ossification; phenotype; southern blotting; transcription factor

Extracellular matrix (ECM) mineralization is a physiologic process in bone and teeth and a pathologic one everywhere else in the body. Pathologic ECM mineralization often has deleterious consequences in conditions such as coronary artery disease and osteoarthdtis two diseases for which no curative treatment is available. Despite the biological importance of ECM mineralization the molecular mechanisms restricting it to bone physiologically remain unknown. In particular gene deletion experiments failed to identify osteoblast-specific genes necessary to initiate bone mineralization while they demonstrated the existence of inhibitors of pathologic ECM mineralization. Two of these inhibitors, Npps and Ank, act by producing inorganic pyrophosphate, an inhibitor of ECM mineralization, and exporting it outside the cells. However, the observation that Npps and Ank are expressed in osteoblasts (data not shown), further complicates our understanding of bone mineralization. The absence of osteoblast-specific proteins initiating bone mineralization together with the expression in osteoblasts of mineralization inhibitors like Npps and Ank that affect phosphate metabolism led us to test the following hypothesis: could the spatial restriction of ECM mineralization to bone be explained, at least in part, by coexpression in osteoblasts of genes that are not osteoblast-specific but that affect phosphate metabolism and ECM assembly? The specific aims are: -To induce ectopic ECM mineralization by ectopic expression of tissue non-specific alkaline phosphatase -To raise TNAP levels in blood to determine if this alone can induce ectopic ECM mineralization -To determine whether ECM mineralization in the growth plate is a molecular determinant of longitudinal growth of the skeleton -To use genetic means to identify substrates for TNAP in bone -To address the role of calcium ions in the initiation of ECM mineralization. We believe that this analysis will greatly enhance our understanding of cartilage and bone ECMs mineralization. This may open novel research avenues to understand the mechanisms leading to the closure of the growth plate at the end of puberty. Finally, it could provide new therapeutic avenues to explore diseases characterized by abnormal or ectopic ECM mineralization such as osteoarthdtis (OA).

细胞外基质（ECM）矿化是骨和牙齿的生理过程，也是身体其他部位的病理过程。病理性ECM矿化通常在诸如冠状动脉疾病和骨关节炎的病症中具有有害后果，这两种疾病没有治愈性治疗。尽管ECM矿化的生物学重要性，但在生理学上限制其进入骨的分子机制仍然未知。特别是基因缺失实验未能确定成骨细胞特异性基因启动骨矿化，而他们证明存在抑制剂的病理ECM矿化。这些抑制剂中的两种，Npps和Ank，通过产生无机焦磷酸盐（ECM矿化的抑制剂）并将其输出到细胞外来起作用。然而，观察到Npps和Ank在成骨细胞中表达（数据未显示），进一步使我们对骨矿化的理解复杂化。缺乏成骨细胞特异性蛋白质启动骨矿化与矿化抑制剂如Npps和Ank，影响磷酸盐代谢的成骨细胞中的表达，导致我们测试以下假设：是否可以解释ECM矿化骨的空间限制，至少部分地，由成骨细胞中的基因的共表达，不是成骨细胞特异性的，但影响磷酸盐代谢和ECM组装？具体目标是：- 通过组织非特异性碱性磷酸酶的异位表达来诱导异位ECM矿化-提高血液中的TNAP水平以确定这是否单独可以诱导异位ECM矿化-确定生长板中的ECM矿化是否是生长板中的细胞的纵向分化的分子决定因素。 骨骼的生长-使用遗传方法鉴定骨中TNAP的底物 - 解决钙离子在ECM矿化启动中的作用。我们相信，这种分析将大大提高我们对软骨和骨ECM矿化的理解。这可能会打开新的研究途径，以了解导致青春期结束时生长板关闭的机制。最后，它可以提供新的治疗途径，探索疾病的特点是异常或异位ECM矿化，如骨关节炎（OA）。