Procollagen Binding Proteins in Age-Dependent LV Remodeling

年龄依赖性左心室重塑中的原胶原结合蛋白

• 批准号: 8440206
• 负责人: Amy D Bradshaw
• 金额: --
• 依托单位: RALPH H JOHNSON VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8440206
• 关键词: Activities of Daily Living; Address; Affect; Age; Aging; Animals; Binding; Binding Proteins; Binding Sites; Cardiac; Cardiovascular Diseases; Cell Aging; Cell Proliferation; Clinical; Collagen; Collagen Receptors; Competitive Binding; Cysteine; Data; Deposition; Development; Elderly; Enzymes; Equilibrium; Exercise; Extracellular Matrix; Fibrillar Collagen; Fibroblasts; Functional disorder; Funding; Gelatinase A; Heart; Heart Diseases; Heart failure; Hypertension; In Vitro; Incidence; Ischemia; Label; Left; Left Ventricular Mass; Left Ventricular Remodeling; Left ventricular structure; Matrix Metalloproteinases; Measurement; Measures; Mediating; Mediator of activation protein; Mus; Myocardial; Myocardium; Osteonectin; Outcome; Patient Care Management; Phenotype; Phosphorylation; Process; Procollagen; Production; Proline; Protein Tyrosine Kinase; Proteins; Radio; Radiolabeled; Regulation; Relative (related person); Signal Pathway; Stream; Structure; Surface; Techniques; Testing; Tissues; Transgenic Organisms; Ventricular; Veterans; age effect; age related; aged; base; cell age; discoidin domain receptor 2; gain of function; improved; in vivo; indexing; interstitial; loss of function; novel; older patient; programs; radiotracer; receptor; research study; senescence

DESCRIPTION (provided by applicant): Left ventricular (LV) structural remodeling, such as changes in LV mass, volume, and geometry, are important predictors of adverse functional and clinical outcomes. Advancing age, independent of concurrent cardiovascular disease, can be associated with significant LV remodeling. Studies in aged animals have shown that increasing age is associated with development of LV concentric remodeling, increased extracellular matrix (ECM) fibrillar collagen content, and significant abnormalities in diastolic function. However, cellular mechanisms by which advanced age leads to cardiac remodeling, particularly a net increase in myocardial collagen content and the development of diastolic dysfunction, have not been completely defined. Regulation of the structure and composition of the collagenous ECM of the myocardium is controlled by cardiac fibroblasts and is regulated at the levels of procollagen synthesis, post-synthetic procollagen processing, and collagen degradation. In aged animals, collagen synthesis is decreased, procollagen processing is increased, and mediators of collagen degradation are generally decreased. In addition, aged fibroblasts demonstrate reduced rates of proliferation consistent with a senescent fibroblast phenotype. In the previous funding period, we identified that expression of SPARC (Secreted Protein Acidic and Rich in Cysteine/osteonectin/BM40), a collagen-binding matricellular protein, was increased in aged myocardium and is a critical factor contributing to elevated collagen content in aged hearts. We also found that SPARC acts to decrease procollagen interaction with cardiac fibroblasts, presumably through decreased engagement of transmembrane collagen receptors. Based on preliminary data, we have identified Discoidin Domain Receptor 2 (DDR2) as a principle collagen receptor engaged in binding collagen and acting in opposition to SPARC. Because DDR2 and SPARC share the same binding site on procollagen, we propose that, in aged myocardium, increases in SPARC expression reduce DDR2 binding to procollagen thus limiting DDR2 binding activity and down-stream signaling pathways. Procollagen binding to DDR2 has been demonstrated to induce fibroblast proliferation and increase production of matrix metalloproteinases (MMP) -2 and -13. Decreased DDR2 activity in aged myocardium is therefore predicted to decrease fibroblast proliferation and production of MMP-2 and -13 thus contributing to the senescent phenotype indicative of aged cardiac fibroblasts. In Aim 1, we will determine whether reductions in DDR2 activity contribute to decreased proliferation and decreased expression of MMP-2 and 13 in aged fibroblasts and whether DDR2 activity is enhanced by decreasing SPARC expression in aged cells. Experiments in Aim 2 will test whether increasing DDR2 activity in aged myocardium, either through over-expression of DDR2 or inhibition of SPARC expression, reverses the senescent fibroblast phenotype in vivo through increasing fibroblast proliferation and production of MMP-2 and 13. Previous studies that have addressed indices of procollagen processing and degradation in aged myocardium have been based primarily on indirect measurements of these processes such as levels of enzymes that process or degrade collagen. In Aim 3, newly developed in vivo radiolabeling techniques will be used to directly quantify changes in procollagen processing and degradation in aged myocardium and determine whether altering DDR2 or SPARC activity influences these processes.

描述（由申请人提供）： 左心室（LV）结构重构，如LV质量、体积和几何形状的变化，是不良功能和临床结局的重要预测因素。年龄的增长，独立于并发的心血管疾病，可能与显著的LV重构相关。在老年动物中的研究表明，年龄的增加与LV向心性重构的发展、细胞外基质（ECM）纤维胶原含量的增加以及舒张功能的显著异常相关。然而，高龄导致心脏重塑的细胞机制，特别是心肌胶原含量的净增加和舒张功能障碍的发展，尚未完全确定。 心肌胶原ECM的结构和组成的调节由心脏成纤维细胞控制，并在前胶原合成、合成后前胶原加工和胶原降解的水平上进行调节。在老年动物中，胶原蛋白合成减少，前胶原蛋白加工增加，胶原蛋白降解的介质通常减少。此外，老化的成纤维细胞表现出与衰老成纤维细胞表型一致的增殖速率降低。在上一个资助期，我们确定了胶原结合基质细胞蛋白-β-胶原蛋白（富含半胱氨酸/骨连接素/BM 40的酸性分泌蛋白）的表达在老年心肌中增加，并且是导致老年心脏中胶原含量升高的关键因素。我们还发现，抑制剂可减少前胶原与心脏成纤维细胞的相互作用，推测是通过减少跨膜胶原受体的参与。基于初步的数据，我们已经确定了盘状结构域受体2（DDR2）作为一个主要的胶原蛋白受体参与结合胶原蛋白，并在反对的胶原蛋白。由于DDR2和DDR4在前胶原上具有相同的结合位点，我们认为，在老年心肌中，DDR4表达的增加减少了DDR2与前胶原的结合，从而限制了DDR2的结合活性和下游信号通路。已证明与DDR2结合的前胶原诱导成纤维细胞增殖并增加基质金属蛋白酶（MMP）-2和-13的产生。因此，预测老化心肌中DDR2活性的降低会降低成纤维细胞增殖和MMP-2和-13的产生，从而有助于指示老化心脏成纤维细胞的衰老表型。在目的1中，我们将确定DDR2活性的降低是否有助于老年成纤维细胞中增殖的降低和MMP-2和13表达的降低，以及DDR2活性是否通过降低老年细胞中MMP-2和13的表达而增强。目标2中的实验将测试通过DDR2的过表达或抑制DDR2表达来增加衰老心肌中的DDR2活性是否通过增加成纤维细胞增殖和MMP-2和MMP-13的产生来逆转体内衰老成纤维细胞表型。以前的研究已经解决了老年心肌中的前胶原蛋白加工和降解的指标，主要是基于这些过程的间接测量，如加工或降解胶原蛋白的酶的水平。在目标3中，新开发的体内放射性标记技术将用于直接定量老化心肌中前胶原加工和降解的变化，并确定改变DDR2或DDR2活性是否会影响这些过程。