Malmström J, Westergren-Thorsson G
Department of Cell and Molecular Biology, Lund University, Sweden.
Glycobiology. 1998 Dec;8(12):1149-55. doi: 10.1093/glycob/8.12.1149.
Heparan sulfate is a molecule that possesses a large structural variability and which has been shown to inhibit the proliferation of fibroblasts in vitro. The aim of this study was to determine whether the anti-proliferative effects of heparan sulfate were exerted by regulation of the activity of the platelet-derived growth factor and/or of the platelet-derived growth factor receptors. Both l-iduronate-rich, anti-proliferative and the l-iduronate-poor, non-anti-proliferative heparan sulfate species, were incubated with confluent human embryonic lung fibroblasts for 24 h. The mRNA levels for PDGF-AA, PDGF-BB, and their receptors were measured. Binding studies were performed with [125I]-PDGF-BB and [125I]-EGF for 2 h at 4 degreesC in cultures preincubated with both types of heparan sulfate for 24 h. In separate experiments, cultures were incubated together with heparan sulfate and [125I]-PDGF-BB for 2 h at 4 degreesC. Increases of two- to threefold in the mRNA levels for both the alpha- and the beta-receptors of PDGF was obtained after treatment with both types of heparan sulfate, whereas the mRNA levels of both the PDGF-AA and the PDGF-BB were essentially unaffected. A sixfold increase in binding was only noted for [125I]-PDGF-BB in cultures pre-treated with the anti-proliferative heparan sulfate for 24 h, whereas no effect was noted with use of the non-anti-proliferative heparan sulfate. Incubating the [125I]-PDGF-BB and the anti-proliferative heparan sulfate together for 2 h resulted in a smaller, threefold increase in binding. This indicates that the anti-proliferative heparan sulfate both stabilizes and increases expression of the PDGF receptors. To investigate whether the increased number of PDGF receptors could affect cell activity, cells were preincubated with anti-proliferative heparan sulfate and then treated with PDGF-BB. This resulted in an increase in mitogenicity compared to cells treated only with PDGF-BB. Neither an increase in binding for [125I-EGF] nor an increase in the mitogenic response of EGF could be observed in cultures pre-treated with the anti-proliferative heparan sulfate. The results indicate that the extracellular matrix itself may regulate important biological phenomena such as cell proliferation and matrix production through affecting the expression of receptors of PDGF, which initiate both stimulatory and inhibitory signals.
硫酸乙酰肝素是一种结构高度可变的分子，已被证明在体外可抑制成纤维细胞的增殖。本研究的目的是确定硫酸乙酰肝素的抗增殖作用是否通过调节血小板衍生生长因子和/或血小板衍生生长因子受体的活性来发挥。将富含L-艾杜糖醛酸、具有抗增殖作用的硫酸乙酰肝素和缺乏L-艾杜糖醛酸、无抗增殖作用的硫酸乙酰肝素与汇合的人胚肺成纤维细胞一起孵育24小时。检测血小板衍生生长因子-AA（PDGF-AA）、血小板衍生生长因子-BB（PDGF-BB）及其受体的mRNA水平。在4℃下，用两种类型的硫酸乙酰肝素预孵育24小时的培养物中，用[125I]-PDGF-BB和[125I]-表皮生长因子（EGF）进行2小时的结合研究。在单独的实验中，培养物与硫酸乙酰肝素和[125I]-PDGF-BB在4℃下一起孵育2小时。用两种类型的硫酸乙酰肝素处理后，PDGF的α和β受体的mRNA水平均增加了两到三倍，而PDGF-AA和PDGF-BB的mRNA水平基本未受影响。仅在用抗增殖硫酸乙酰肝素预处理24小时的培养物中，观察到[125I]-PDGF-BB的结合增加了六倍，而使用无抗增殖作用的硫酸乙酰肝素则未观察到影响。将[125I]-PDGF-BB与抗增殖硫酸乙酰肝素一起孵育2小时，导致结合增加幅度较小，为三倍。这表明抗增殖硫酸乙酰肝素既稳定又增加了PDGF受体的表达。为了研究PDGF受体数量的增加是否会影响细胞活性，细胞先用抗增殖硫酸乙酰肝素预孵育，然后用PDGF-BB处理。与仅用PDGF-BB处理的细胞相比，这导致有丝分裂活性增加。在用抗增殖硫酸乙酰肝素预处理的培养物中，未观察到[125I-EGF]结合增加，也未观察到EGF的有丝分裂反应增加。结果表明，细胞外基质本身可能通过影响PDGF受体的表达来调节重要的生物学现象，如细胞增殖和基质产生，而PDGF受体可启动刺激和抑制信号。
