Hill D J, Logan A, McGarry M, De Sousa D
Lawson Research Institute, St Joseph's Health Centre, London, Ontario, Canada.
J Endocrinol. 1992 Jun;133(3):363-73. doi: 10.1677/joe.0.1330363.
Chondrogenesis is thought to be controlled by interactions between circulating anabolic hormones and locally produced peptide growth factors, and involves ordered changes in matrix composition which ultimately allow endochondral calcification. We have used a model of isolated ovine fetal growth-plate chondrocytes to examine the actions and interactions of basic fibroblast growth factor (basic FGF), insulin-like growth factors-I and -II (IGF-I and -II), insulin and transforming growth factor-beta 1 (TGF-beta 1) on total protein, collagen or non-collagenous protein and sulphated glycosaminoglycan synthesis. These parameters were determined by assessment of the incorporation by monolayer cultures of early passage chondrocytes of [3H]leucine, [14C]proline and [35S]sulphate respectively, followed by partial molecular characterization. Basic FGF enhanced total protein synthesis with a half-maximal effective concentration of 270 +/- 60 pmol/l (mean +/- S.E.M., four animals) and was sixfold more active on a molar basis than IGF-I or insulin, and 28-fold more active that IGF-II which is the endogenously synthesized IGF. The actions of basic FGF were additive to those of IGF-I or insulin. More detailed analysis of extracellular-matrix component synthesis showed that basic FGF, IGF-I and insulin each caused significant increases in the synthesis of collagen and sulphated glycosaminoglycans. TGF-beta 1 had no effect on total protein synthesis by chondrocytes when present alone at concentrations of 200 pmol/l or less, but was inhibitory at 400 pmol/l. However, the use of this parameter masked a stimulatory action of 50 or 100 pmol TGF-beta 1 on sulphated glycosaminoglycan synthesis and a relative shift in the ratio of collagen: non-collagenous protein synthesis in favour of the former. A synergistic interaction existed between TGF-beta 1 (20-100 pmol/l) and basic FGF which potentiated total protein and collagen synthesis, and their actions on sulphated glycosaminoglycan production were additive. The same concentrations of TGF-beta 1 inhibited the ability of IGF-I or insulin to stimulate total protein or collagen synthesis, but were additive to their stimulatory effects on sulphated glycosaminoglycan synthesis. The results suggest that matrix-molecule composition and the anabolic status of the epiphyseal growth-plate may be modulated in utero by multiple interactions between peptide growth factors produced locally, such as basic FGF, IGF-II and TGF-beta 1, and circulating hormones such as insulin and IGF-I.
软骨形成被认为受循环中的合成代谢激素与局部产生的肽生长因子之间相互作用的控制，并且涉及基质成分的有序变化，最终导致软骨内钙化。我们使用分离的绵羊胎儿生长板软骨细胞模型来研究碱性成纤维细胞生长因子（碱性FGF）、胰岛素样生长因子-I和-II（IGF-I和-II）、胰岛素以及转化生长因子-β1（TGF-β1）对总蛋白、胶原蛋白或非胶原蛋白以及硫酸化糖胺聚糖合成的作用和相互作用。这些参数通过分别评估早期传代软骨细胞单层培养物对[3H]亮氨酸、[14C]脯氨酸和[35S]硫酸盐的掺入来确定，随后进行部分分子特征分析。碱性FGF增强总蛋白合成，半数有效浓度为270±60 pmol/l（平均值±标准误，四只动物），在摩尔基础上比IGF-I或胰岛素活性高6倍，比内源性合成的IGF-II活性高28倍。碱性FGF的作用与IGF-I或胰岛素的作用相加。对细胞外基质成分合成的更详细分析表明，碱性FGF、IGF-I和胰岛素各自导致胶原蛋白和硫酸化糖胺聚糖合成显著增加。当单独存在浓度为200 pmol/l或更低时，TGF-β1对软骨细胞的总蛋白合成没有影响，但在400 pmol/l时具有抑制作用。然而，使用这个参数掩盖了50或100 pmol TGF-β1对硫酸化糖胺聚糖合成的刺激作用以及胶原蛋白：非胶原蛋白合成比例向有利于前者的相对转变。TGF-β1（2-100 pmol/l）与碱性FGF之间存在协同相互作用，增强了总蛋白和胶原蛋白合成，并且它们对硫酸化糖胺聚糖产生的作用是相加的。相同浓度的TGF-β1抑制IGF-I或胰岛素刺激总蛋白或胶原蛋白合成的能力，但对它们对硫酸化糖胺聚糖合成的刺激作用是相加的。结果表明，骨骺生长板的基质分子组成和合成代谢状态可能在子宫内通过局部产生的肽生长因子（如碱性FGF、IGF-II和TGF-β1）与循环激素（如胰岛素和IGF-I）之间的多种相互作用进行调节。
