Raisz L G
Lowell P. Weicker, Jr. General Clinical Research Center, University of Connecticut Health Center, MC-2806, 263 Farmington Ave., Farmington, CT 06030, USA.
Clin Chem. 1999 Aug;45(8 Pt 2):1353-8.
The skeleton is a metabolically active organ that undergoes continuous remodeling throughout life. This remodeling is necessary both to maintain the structural integrity of the skeleton and to subserve its metabolic functions as a storehouse of calcium and phosphorus. These dual functions often come into conflict under conditions of changing mechanical forces or metabolic and nutritional stress. The bone remodeling cycle involves a complex series of sequential steps that are highly regulated. The "activation" phase of remodeling is dependent on the effects of local and systemic factors on mesenchymal cells of the osteoblast lineage. These cells interact with hematopoietic precursors to form osteoclasts in the "resorption" phase. Subsequently, there is a "reversal" phase during which mononuclear cells are present on the bone surface. They may complete the resorption process and produce the signals that initiate formation. Finally, successive waves of mesenchymal cells differentiate into functional osteoblasts, which lay down matrix in the "formation" phase. The effects of calcium-regulating hormones on this remodeling cycle subserve the metabolic functions of the skeleton. Other systemic hormones control overall skeletal growth. The responses to changes in mechanical force and repair of microfractures, as well as the maintenance of the remodeling cycle, are determined locally by cytokines, prostaglandins, and growth factors. Interactions between systemic and local factors are important in the pathogenesis of osteoporosis as well as the skeletal changes in hyperparathyroidism and hyperthyroidism. Local factors are implicated in the pathogenesis of the skeletal changes associated with immobilization, inflammation, and Paget disease of bone.
骨骼是一个具有代谢活性的器官，在整个生命过程中不断进行重塑。这种重塑对于维持骨骼的结构完整性以及作为钙和磷储存库发挥其代谢功能都是必要的。在机械力变化或代谢及营养应激的情况下，这两种功能常常相互冲突。骨重塑周期涉及一系列复杂的连续步骤，且受到高度调控。重塑的“激活”阶段取决于局部和全身因素对成骨细胞谱系间充质细胞的影响。在“吸收”阶段，这些细胞与造血前体细胞相互作用形成破骨细胞。随后是一个“逆转”阶段，在此期间单核细胞出现在骨表面。它们可能完成吸收过程并产生启动形成的信号。最后，间充质细胞的连续波分化为功能性成骨细胞，在“形成”阶段沉积基质。钙调节激素对这个重塑周期的作用有助于骨骼的代谢功能。其他全身激素控制整体骨骼生长。对机械力变化和微骨折修复的反应以及重塑周期的维持，在局部由细胞因子、前列腺素和生长因子决定。全身和局部因素之间的相互作用在骨质疏松症的发病机制以及甲状旁腺功能亢进和甲状腺功能亢进的骨骼变化中都很重要。局部因素与与固定、炎症和骨Paget病相关的骨骼变化的发病机制有关。
