D'avis P Y, Frazier C R, Shapiro J R, Fedarko N S
Division of Geriatrics, Department of Medicine, Room 5A-50 JHAAC, Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA.
Biochem J. 1997 Jun 15;324 ( Pt 3)(Pt 3):753-60. doi: 10.1042/bj3240753.
The role of insulin-like growth factor I (IGF-I) in extracellular matrix metabolism was studied in both proliferating and confluent human osteoblast-like cultures derived from donors of different ages. In proliferating cultures, recombinant human (rh)IGF-I was found to increase the incorporation of [3H]thymidine in a dose- and age-dependent manner. To study cell proliferation dynamically, continuous growth curves with and without rhIGF-I were modelled by a modified logistic function. Increasing doses of rhIGF-I decreased the lag time and maximal growth rates, whereas plateau values decreased only at the highest dose (100 ng/ml). In post-proliferative cell strains, rhIGF-I (0.1-100 ng/ml) increased levels of type I collagen, biglycan and decorin, and to a smaller extent fibronectin and thrombospondin, whereas it decreased the levels of hyaluronan and a versican-like proteoglycan when protein and proteoglycan metabolism were followed by steady-state radiolabelling with [3H]proline, [3H]glucosamine or [35S]sulphate. These responses to rhIGF-I were found to be age-dependent, with osteoblast-like cells derived from younger patients being more responsive to rhIGF-I. When extracellular matrix turnover was analysed by pulse-chase experiments, rhIGF-I had no effect. The steady-state levels of collagen, decorin, hyaluronan and a versican-like proteoglycan for bone cells treated with rhIGF-I on day 7 in culture were equivalent to levels of these matrix components in untreated osteoblasts grown for 14 days. These results are consistent with rhIGF-I's altering cellular proliferative capacity and matrix synthesis, causing a change in the osteoblast differentiated state.
在源自不同年龄供体的增殖期和汇合期人成骨细胞样培养物中，研究了胰岛素样生长因子I（IGF-I）在细胞外基质代谢中的作用。在增殖期培养物中，发现重组人（rh）IGF-I以剂量和年龄依赖性方式增加[3H]胸腺嘧啶核苷的掺入。为了动态研究细胞增殖，用改良的逻辑函数对有和没有rhIGF-I的连续生长曲线进行建模。rhIGF-I剂量增加会缩短延迟时间并提高最大生长速率，而平台期值仅在最高剂量（100 ng/ml）时降低。在增殖后期细胞株中，当用[3H]脯氨酸、[3H]氨基葡萄糖或[35S]硫酸盐进行稳态放射性标记来追踪蛋白质和蛋白聚糖代谢时，rhIGF-I（0.1 - 100 ng/ml）增加了I型胶原、双糖链蛋白聚糖和核心蛋白聚糖的水平，在较小程度上增加了纤连蛋白和血小板反应蛋白的水平，而降低了透明质酸和一种类多功能蛋白聚糖的水平。发现这些对rhIGF-I的反应具有年龄依赖性，源自年轻患者的成骨细胞样细胞对rhIGF-I更敏感。当通过脉冲追踪实验分析细胞外基质周转时，rhIGF-I没有作用。培养第7天用rhIGF-I处理的骨细胞中，胶原、核心蛋白聚糖透明质酸和一种类多功能蛋白聚糖的稳态水平与未处理的成骨细胞生长14天时这些基质成分的水平相当。这些结果与rhIGF-I改变细胞增殖能力和基质合成、导致成骨细胞分化状态改变是一致的。
