Dombrowski Christian, Song Shu Jun, Chuan Peiying, Lim Xinhong, Susanto Evelyn, Sawyer Amber A, Woodruff Maria A, Hutmacher Dietmar W, Nurcombe Victor, Cool Simon M
Stem Cells and Tissue Repair Group, Institute of Medical Biology, A*STAR, Singapore.
Stem Cells Dev. 2009 May;18(4):661-70. doi: 10.1089/scd.2008.0157.
The growth and differentiation of mesenchymal stem cells (MSCs) is controlled by various growth factors, the activities of which can be modulated by heparan sulfates (HSs). We have previously noted the necessity of sulfated glycosaminoglycans for the fibroblast growth factor type 2 (FGF-2)-stimulated differentiation of osteoprogenitor cells. Here we show that exogenous application of HS to cultures of primary rat MSCs stimulates their proliferation, leading to increased expression of osteogenic markers and enhanced bone nodule formation. FGF-2 can also increase the proliferation, and osteogenic differentiation of rat bone marrow stem cells (rMSCs) when applied exogenously during their linear growth. However, as opposed to exogenous HS, the continuous use of FGF-2 during in vitro differentiation completely blocked rMSC mineralization. We show that the effects of both FGF-2 and HS are mediated through FGF receptor 1 (FGFR1) and that inhibition of signaling through this receptor arrests cell growth, resulting in the cells being unable to reach the critical density necessary to induce differentiation. Blocking FGFR1 signaling in postconfluent osteogenic cultures significantly increased calcium deposition. Taken together our data suggest that FGFR1 signaling plays an important role during osteogenic differentiation, first by stimulating cell growth that is closely followed by an inhibitory effect once the cells have reached confluence. It also confirms the importance of HS as a coreceptor for the signaling of endogenous FGF-2 and suggests that purified glycosaminoglycans may be attractive alternatives to growth factors for improved ex vivo growth and differentiation of MSCs.
间充质干细胞（MSCs）的生长和分化受多种生长因子调控，而硫酸乙酰肝素（HSs）可调节这些生长因子的活性。我们之前已经注意到，硫酸化糖胺聚糖对于成骨祖细胞在成纤维细胞生长因子2（FGF - 2）刺激下的分化是必需的。在此我们表明，向原代大鼠MSCs培养物中外源应用HS可刺激其增殖，导致成骨标志物表达增加以及骨结节形成增强。当在大鼠骨髓干细胞（rMSCs）线性生长期间外源应用FGF - 2时，它也可增加rMSCs的增殖和成骨分化。然而，与外源HS相反，在体外分化过程中持续使用FGF - 2会完全阻断rMSC矿化。我们表明，FGF - 2和HS的作用均通过FGF受体1（FGFR1）介导，并且抑制通过该受体的信号传导会阻止细胞生长，导致细胞无法达到诱导分化所需的临界密度。在汇合后成骨培养物中阻断FGFR1信号传导可显著增加钙沉积。综合我们的数据表明，FGFR1信号传导在成骨分化过程中起重要作用，首先通过刺激细胞生长，一旦细胞达到汇合状态随后便产生抑制作用。这也证实了HS作为内源性FGF - 2信号传导的共受体的重要性，并表明纯化的糖胺聚糖可能是生长因子的有吸引力的替代品，可用于改善MSCs的体外生长和分化。
