PDF(Pubmed)
Abstract：
Vascular calcification has a global health impact that is closely linked to bone loss. The Receptor Activator of Nuclear Factor Kappa B (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system, fundamental for bone metabolism, also plays an important role in vascular calcification. The Leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4), a novel receptor for RANKL, regulates bone remodeling, and it appears to be involved in vascular calcification. Besides RANKL, LGR4 interacts with R-spondins (RSPOs), which are known for their roles in bone but are less understood in vascular calcification. Studies were conducted in rats with chronic renal failure fed normal or high phosphorus diets for 18 weeks, with and without control of circulating parathormone (PTH) levels, resulting in different degrees of aortic calcification. Additionally, vascular smooth muscle cells (VSMCs) were cultured under non-calcifying (1 mM phosphate) and calcifying (3 mM phosphate) media with different concentrations of PTH. To explore the role of RANKL in VSMC calcification, increasing concentrations of soluble RANKL were added to non-calcifying and calcifying media. The effects mediated by RANKL binding to its receptor LGR4 were investigated by silencing the LGR4 receptor in VSMCs. Furthermore, the gene expression of the RANK/RANKL/OPG system and the ligands of LGR4 was assessed in human epigastric arteries obtained from kidney transplant recipients with calcification scores (Kauppila Index). Increased aortic calcium in rats coincided with elevated systolic blood pressure, upregulated Lgr4 and Rankl gene expression, downregulated Opg gene expression, and higher serum RANKL/OPG ratio without changes in Rspos gene expression. Elevated phosphate in vitro increased calcium content and expression of Rankl and Lgr4 while reducing Opg. Elevated PTH in the presence of high phosphate exacerbated the increase in calcium content. No changes in Rspos were observed under the conditions employed. The addition of soluble RANKL to VSMCs induced genotypic differentiation and calcification, partly prevented by LGR4 silencing. In the epigastric arteries of individuals presenting vascular calcification, the gene expression of RANKL was higher. While RSPOs show minimal impact on VSMC calcification, RANKL, interacting with LGR4, drives osteogenic differentiation in VSMCs, unveiling a novel mechanism beyond RANKL-RANK binding.
摘要：
血管钙化具有与骨丢失密切相关的全球健康影响。核因子κB受体激活因子(RANK)/RANK配体(RANKL)/骨保护素(OPG)系统,骨代谢的基础，在血管钙化中也起着重要作用。富含亮氨酸的含重复序列的G蛋白偶联受体4（LGR4），一种新的RANKL受体，调节骨骼重塑，它似乎与血管钙化有关。除了RANKL,LGR4与R-spondins(RSPO)相互作用，众所周知，它们在骨骼中的作用，但在血管钙化中却鲜为人知。研究在慢性肾功能衰竭的大鼠中进行了正常或高磷饮食18周，有或没有控制循环副甲状腺激素（PTH）水平，导致不同程度的主动脉钙化。此外,血管平滑肌细胞(VSMC)在含不同浓度PTH的非钙化(1mM磷酸盐)和钙化(3mM磷酸盐)培养基中培养。探讨RANKL在VSMC钙化中的作用,将增加浓度的可溶性RANKL添加到非钙化和钙化培养基中。通过沉默VSMC中的LGR4受体来研究RANKL与其受体LGR4结合所介导的作用。此外，在有钙化评分(Kauppila指数)的肾移植受者的人上腹部动脉中评估了RANK/RANKL/OPG系统和LGR4配体的基因表达.大鼠主动脉钙升高与收缩压升高同时发生,上调Lgr4和Rankl基因表达，下调Opg基因表达，和更高的血清RANKL/OPG比率，而Rspos基因表达没有变化。体外升高的磷酸盐增加了钙含量和Rankl和Lgr4的表达，同时降低了Opg。在高磷酸盐存在下PTH升高加剧了钙含量的增加。在所采用的条件下没有观察到Rspos的变化。可溶性RANKL添加到VSMCs诱导基因型分化和钙化，部分由LGR4沉默阻止。在呈现血管钙化的个体的上腹部动脉中，RANKL基因表达较高。虽然RSPO对VSMC钙化的影响最小，RANKL,与LGR4相互作用，驱动VSMC中的成骨分化，揭示了超越RANKL-RANK绑定的新颖机制。
