Grimsrud C D, Rosier R N, Puzas J E, Reynolds P R, Reynolds S D, Hicks D G, O'Keefe R J
Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, New York 14642, USA.
J Orthop Res. 1998 Mar;16(2):247-55. doi: 10.1002/jor.1100160212.
Although the bone morphogenetic proteins stimulate chondrogenesis, little is known regarding their expression and regulation in growth-plate chondrocytes. The expression of bone morphogenetic protein-7 was examined in chick growth-plate chondrocyte cultures. Low basal levels of bone morphogenetic protein-7 mRNA and protein expression were stimulated by increasing doses of all-trans retinoic acid, a metabolite of vitamin A. The addition of 10 microM retinoic acid resulted in approximately a 6-fold increase in bone morphogenetic protein-7 mRNA levels. In contrast, other growth regulators, including basic fibroblast growth factor, transforming growth factor-beta, vitamin D, bone morphogenetic protein-6, bone morphogenetic protein-7, and parathyroid hormone-related peptide, did not alter bone morphogenetic protein-7 transcript levels. The increase in bone morphogenetic protein-7 transcripts, although present at 6 hours, was maximal following a 12-hour exposure to retinoic acid. Retinoic acid induction of bone morphogenetic protein-7 transcript levels was dependent on protein synthesis because the induction could be blocked by cyclohexamide. In maturationally distinct subpopulations of chondrocytes separated by countercurrent centrifugal elutriation, retinoic acid markedly induced bone morphogenetic protein-7 mRNA levels in the least differentiated chondrocytes but had no effect in the most terminally differentiated hypertrophic chondrocytes. Immunohistochemical localization of bone morphogenetic protein-7 demonstrates its expression throughout the developing and adolescent growth plate consistent with the constitutive pattern of expression seen in isolated chondrocytes. The addition of exogenous bone morphogenetic protein-7 to chondrocyte cultures stimulated maturation in undifferentiated chondrocyte populations. The data support a role for bone morphogenetic protein-7 as an autocrine regulator of chondrocyte maturation in the growth plate. Regulation of bone morphogenetic protein-7 by retinoic acid may be important in normal growth and development as well as in pathologic conditions of an excess or deficiency of vitamin A.
尽管骨形态发生蛋白可刺激软骨形成，但关于它们在生长板软骨细胞中的表达和调控却知之甚少。本研究检测了鸡生长板软骨细胞培养物中骨形态发生蛋白-7的表达情况。维生素A的代谢产物全反式维甲酸剂量增加时，可刺激骨形态发生蛋白-7 mRNA和蛋白表达的基础水平升高。添加10微摩尔/升的维甲酸可使骨形态发生蛋白-7 mRNA水平增加约6倍。相比之下，其他生长调节因子，包括碱性成纤维细胞生长因子、转化生长因子-β、维生素D、骨形态发生蛋白-6、骨形态发生蛋白-7和甲状旁腺激素相关肽，均未改变骨形态发生蛋白-7转录本水平。骨形态发生蛋白-7转录本水平的增加在6小时时即可出现，但在暴露于维甲酸12小时后达到最大值。维甲酸诱导骨形态发生蛋白-7转录本水平依赖于蛋白质合成，因为这种诱导可被环己酰亚胺阻断。在通过逆流离心淘析分离的成熟程度不同的软骨细胞亚群中，维甲酸显著诱导了分化程度最低的软骨细胞中骨形态发生蛋白-7 mRNA水平，但对终末分化程度最高的肥大软骨细胞没有影响。骨形态发生蛋白-7的免疫组织化学定位显示其在整个发育中和青春期生长板中均有表达，这与在分离的软骨细胞中观察到的组成性表达模式一致。向软骨细胞培养物中添加外源性骨形态发生蛋白-7可刺激未分化软骨细胞群体的成熟。这些数据支持骨形态发生蛋白-7作为生长板软骨细胞成熟的自分泌调节因子的作用。维甲酸对骨形态发生蛋白-7的调节在正常生长发育以及维生素A过量或缺乏的病理状况中可能都很重要。
