O'Keefe R J, Crabb I D, Puzas J E, Rosier R N
Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, NY 14642.
J Orthop Res. 1994 May;12(3):299-310. doi: 10.1002/jor.1100120302.
The local tissue metabolism is controlled through the complex interaction between systemic and local growth factors. In recent years, an increasing number of autocrine or paracrine growth regulators have been identified in physeal cartilage. While these factors act to alter chondrocytes phenotypically and presumably are important mediators in the process of endochondral ossification, the manner in which they interact with the systemically regulated growth factor insulin-like growth factor-I is unknown. In the present study, the interactive effects of insulin-like growth factor-I with transforming growth factor-beta 1 or basic fibroblast growth factor were examined in short-term monolayer cultures of chick growth plate chondrocytes. [3H]thymidine incorporation was maximally stimulated 11-fold by fibroblast growth factor (10 ng/ml) and 3.5-fold by transforming growth factor-beta 1 following a 24-hour exposure in serum-containing cultures. The effects of transforming growth factor-beta 1 and fibroblast growth factor at both high and low concentrations were enhanced in a dose-dependent manner by insulin-like growth factor-I, with a 40-50% increase in DNA synthesis in the presence of 100 ng/ml of insulin-like growth factor-I. Since insulin-like growth factor-I increased [3H]thymidine incorporation after 48 hours (50% increase) but not after 24 hours of exposure, these observations represent a synergistic interaction. Total DNA in cultures treated for 5 days confirmed the modulating effect of insulin-like growth factor-I with transforming growth factor-beta 1 and fibroblast growth factor. The growth factors were further examined for their effects on markers of chondrocyte differentiation. While all three caused a dose-dependent inhibition of alkaline phosphatase activity, the effects of insulin-like growth factor-I were additive only to those of transforming growth factor-beta 1 and fibroblast growth factor. Similarly, insulin-like growth factor-I did not affect the sulfate incorporation stimulated by fibroblast growth factor or transforming growth factor-beta 1. Insulin-like growth factor-I had no effect on total protein synthesis after 24 hours and, although type-II collagen mRNA levels were stimulated, it had no effect on type-X collagen mRNA, as determined by quantitative in situ hybridization. Finally, insulin-like growth factor-I did not alter the dose-dependent stimulation of noncollagen protein synthesis and the inhibition of collagen synthesis caused by fibroblast growth factor and transforming growth factor-beta 1 in 24-hour cultures. Thus, the data suggest that insulin-like growth factor-I may have a role in augmenting the effects of other growth factors found in cartilage.(ABSTRACT TRUNCATED AT 400 WORDS)
局部组织代谢是通过全身和局部生长因子之间复杂的相互作用来控制的。近年来，在生长板软骨中已鉴定出越来越多的自分泌或旁分泌生长调节因子。虽然这些因子可改变软骨细胞的表型，并且可能是软骨内骨化过程中的重要介质，但它们与受全身调节的生长因子胰岛素样生长因子-I相互作用的方式尚不清楚。在本研究中，在鸡生长板软骨细胞的短期单层培养中检测了胰岛素样生长因子-I与转化生长因子-β1或碱性成纤维细胞生长因子的相互作用。在含血清的培养物中暴露24小时后，成纤维细胞生长因子（10 ng/ml）可使[3H]胸苷掺入量最大刺激11倍，转化生长因子-β1可使其刺激3.5倍。胰岛素样生长因子-I以剂量依赖性方式增强了高浓度和低浓度的转化生长因子-β1和成纤维细胞生长因子的作用，在存在100 ng/ml胰岛素样生长因子-I的情况下，DNA合成增加40-50%。由于胰岛素样生长因子-I在暴露48小时后增加了[3H]胸苷掺入量（增加50%），但在暴露24小时后没有增加，这些观察结果代表了一种协同相互作用。处理5天的培养物中的总DNA证实了胰岛素样生长因子-I对转化生长因子-β1和成纤维细胞生长因子的调节作用。进一步研究了这些生长因子对软骨细胞分化标志物的影响。虽然所有三种因子均导致碱性磷酸酶活性的剂量依赖性抑制，但胰岛素样生长因子-I的作用仅与转化生长因子-β1和成纤维细胞生长因子的作用相加。同样，胰岛素样生长因子-I不影响成纤维细胞生长因子或转化生长因子-β1刺激的硫酸盐掺入。胰岛素样生长因子-I在24小时后对总蛋白合成没有影响，并且尽管II型胶原mRNA水平受到刺激，但通过定量原位杂交确定，它对X型胶原mRNA没有影响。最后，胰岛素样生长因子-I在24小时培养中没有改变成纤维细胞生长因子和转化生长因子-β1引起的非胶原蛋白合成的剂量依赖性刺激和胶原蛋白合成的抑制。因此，数据表明胰岛素样生长因子-I可能在增强软骨中发现的其他生长因子的作用方面发挥作用。（摘要截短为400字）
