PDGF, bFGF and IGF-I stimulate the proliferation of intervertebral disc cells in vitro via the activation of the ERK and Akt signaling pathways
PDGF, bFGF and IGF-I stimulate the proliferation of intervertebral disc cells in vitro via the activation of the ERK and Akt signaling pathways
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DOI：
10.1007/s00586-007-0408-9
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发表时间：
2007-11-01
影响因子：
2.8
通讯作者：
Kletsas, Dimitris
中科院分区：
文献类型：
--
作者：
Pratsinis, Harris;Kletsas, Dimitris
椎间盘退变通常以细胞增殖增加为特征，可能是一种组织再生反应。尽管许多生长因子及其受体在椎间盘中正常表达，并在退变过程中普遍过度表达，但并不是所有的生长因子及其受体对IVD细胞增殖的影响都得到了深入的研究。本文研究了三种有丝分裂原，即血小板衍生生长因子(PDGF)、碱性成纤维细胞生长因子(BFGF)和胰岛素样生长因子-I(IGF-I)对体外培养的牛尾髓核(NP)和纤维环(AF)细胞的促增殖作用，以及激活主要的细胞内信号转导通路的作用。PDGF、bFGF和IGF-I以剂量依赖的方式诱导静止期IVD细胞的DNA合成。PDGF的刺激作用最强，但三种因素同时作用的刺激作用仅略高于PDGF单独作用。三种生长因子均可立即磷酸化细胞外信号调节蛋白激酶(ERKs)，尤其是bFGF刺激可使ERK持续磷酸化。此外，这三种生长因子在刺激后立即诱导Thr308和Ser473残基Akt的磷酸化，尽管bFGF诱导的磷酸化比PDGF和IGF-I诱导的弱得多。此外，MEK抑制剂PD98059和PI 3-K抑制剂Wortmannin分别阻断生长因子诱导的IVD细胞ERK和Akt的磷酸化。抑制MEK/ERK或PI3-K/Akt信号通路可使PDGF、bFGF或IGF-I对IVD细胞的促增殖作用明显减弱，而同时抑制这两种信号通路则可完全消除这些生长因子的促分裂活性。上述三种生长因子在NP和AF细胞培养中的作用相似。综上所述，上述结果表明PDGF、bFGF和IGF-I通过ERK和Akt信号通路刺激IVD细胞的增殖。
Intervertebral disc (IVD) degeneration is frequently characterized by increased cell proliferation, probably as a tissue regenerative response. Although many growth factors and their receptors have been shown to be expressed normally in the disc, and generally to be over-expressed during degeneration, not all of them have been thoroughly studied concerning their effects on IVD cell proliferation. In the present report, three potent mitogens, platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF) and insulin-like growth factor-I (IGF-I) are examined regarding their capacity to induce proliferation in vitro of bovine coccygeal nucleus pulposus (NP) and annulus fibrosus (AF) cells, as well as to activate major intracellular signal transduction pathways. PDGF, bFGF and IGF-I were found to induce DNA synthesis in quiescent IVD cells in a dose-dependent manner. Maximum stimulation was induced by PDGF, while stimulation by all three factors simultaneously exceeded only slightly that caused by PDGF alone. All three growth factors were shown to phosphorylate immediately extracellular-signal regulated kinases (ERKs), while the stimulation by bFGF especially resulted in sustained ERK phosphorylation. Furthermore, all three growth factors induced phosphorylation of Akt in both Thr308 and Ser473 residues immediately after stimulation, although bFGF-induced phosphorylation was much weaker than that provoked by PDGF and IGF-I. In addition, the MEK inhibitor PD98059 and the PI 3-K inhibitor wortmannin were shown to block growth factor-induced ERK- and Akt-phosphorylation, respectively, in IVD cells. Inhibition of the MEK/ERK or the PI 3-K/Akt pathways provoked a significant decline of the proliferative effects of PDGF, bFGF or IGF-I on IVD cell cultures, while the simultaneous inhibition of both signaling pathways abolished completely the mitogenicity of these growth factors. The above effects of the three growth factors were reproduced similarly in both NP and AF cell cultures. Overall, the above results indicate that PDGF, bFGF and IGF-I stimulate the proliferation of IVD cells via the ERK and Akt signaling pathways.