Martínez P, Moreno I, De Miguel F, Vila V, Esbrit P, Martínez M E
Biochemistry Division, Hospital La Paz, Madrid, Spain.
Bone. 2001 Jul;29(1):35-41. doi: 10.1016/s8756-3282(01)00479-3.
Age-related osteopenia is known to occur differently throughout the skeleton. In the present study, we examine the influence of donor age (<50 and >50 years), and bone structure (cortical vs. trabecular) on osteocalcin and vitamin D receptor (VDR) expression in primary cultures of human osteoblastic cells (hOB) cells. Cells were isolated from trabecular bone samples obtained from donors undergoing either knee (mainly trabecular) (n = 22; 4 <50 years, 18 >50 years) or hip (mainly cortical) (n = 16; 6 <50 years, 10 >50 years) arthroplasty. Pooling the results from knee and hip hOB cell cultures, we found that secreted osteocalcin was higher in hOB cells from the younger donors, compared with that in older donors, and peaked after stimulation with 10(-6)--10(-8) mol/L 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)]. In cells from the latter donors, this secretion was maximal after 10(-6) mol/L 1,25(OH)(2)D(3) treatment. On the other hand, using reverse transcription followed by polymerase chain reaction, baseline osteocalcin mRNA was found to be lower in hOB cells from the older donors than in those from younger donors. After treatment with 10(-6)--10(-8) mol/L 1,25(OH)(2)D(3), osteocalcin mRNA increased over baseline in all groups of hOB cells studied. In age-matched cultures, both basal and 10(-6)--10(-8) mol/L 1,25(OH)(2)D(3)-stimulated osteocalcin mRNA showed similar values in hOB cells from both skeletal sites in younger donors. However, in the older donors, baseline as well as 10(-8) mol/L 1,25(OH)(2)D(3)-stimulated osteocalcin mRNA were higher in knee hOB cells than in hip hOB cells. Furthermore, baseline VDR mRNA expression was also higher in the former cells than in the latter cells in the older group. Considering the influence of donor age at each skeletal site of origin, we found lower baseline osteocalcin and VDR mRNA levels in hip hOB cells in the older group than in the younger group. Our findings indicate that the response of osteocalcin secretion and its mRNA to physiological doses of 1,25(OH)(2)D(3) decreases with aging and is associated with decreased VDR mRNA expression in hOB cells from mainly cortical bone.
众所周知，与年龄相关的骨质减少在整个骨骼中的发生情况有所不同。在本研究中，我们考察了供体年龄（<50岁和>50岁）以及骨结构（皮质骨与小梁骨）对人成骨细胞（hOB）原代培养物中骨钙素和维生素D受体（VDR）表达的影响。细胞从接受膝关节（主要为小梁骨）（n = 22；4例<50岁，18例>50岁）或髋关节（主要为皮质骨）（n = 16；6例<50岁，10例>50岁）置换术的供体所获取的小梁骨样本中分离得到。汇总膝关节和髋关节hOB细胞培养的结果，我们发现，与老年供体的hOB细胞相比，年轻供体的hOB细胞分泌的骨钙素更高，并且在用10(-6) - 10(-8) mol/L 1,25 - 二羟维生素D(3) [1,25(OH)(2)D(3)]刺激后达到峰值。在老年供体的细胞中，这种分泌在10(-6) mol/L 1,25(OH)(2)D(3)处理后达到最大值。另一方面，通过逆转录随后进行聚合酶链反应发现，老年供体的hOB细胞中骨钙素mRNA的基线水平低于年轻供体的hOB细胞。在用10(-6) - 10(-8) mol/L 1,25(OH)(2)D(3)处理后，所研究的所有hOB细胞组中骨钙素mRNA均高于基线水平。在年龄匹配的培养物中，年轻供体两个骨骼部位的hOB细胞中，基础和10(-6) - 10(-8) mol/L 1,25(OH)(2)D(3)刺激的骨钙素mRNA显示出相似的值。然而，在老年供体中，膝关节hOB细胞的基线以及10(-8) mol/L 1,25(OH)(2)D(3)刺激的骨钙素mRNA高于髋关节hOB细胞。此外，在老年组中，前者细胞的基线VDR mRNA表达也高于后者细胞。考虑到每个骨骼起源部位供体年龄的影响，我们发现老年组髋关节hOB细胞中骨钙素和VDR mRNA的基线水平低于年轻组。我们的研究结果表明，骨钙素分泌及其mRNA对生理剂量的1,25(OH)(2)D(3)的反应随年龄增长而降低，并且与主要来自皮质骨的hOB细胞中VDR mRNA表达降低有关。
