Johnson S E, Allen R E
Department of Animal Sciences, University of Arizona, Tucson 85721, USA.
Exp Cell Res. 1995 Aug;219(2):449-53. doi: 10.1006/excr.1995.1251.
Specific, high-affinity binding of FGF2 was evaluated in cultured skeletal muscle satellite cells from young (3- to 4-week-old) and adult (9- to 12-month-old) rats prior to the first division in culture. Specific binding of FGF2 was detected on satellite cells from young rats at 18 h postplating, the earliest time examined, but specific binding was not detectable until 42 h on satellite cells from old rats. This correlates well with the delayed entry into the cell cycle exhibited by adult satellite cells and with the ability of satellite cells from rats of these ages to proliferate in response to FGF2. Patterns of tyrosine phosphorylation in whole cell extracts, following stimulation by FGF2, indicated specific FGF2 phosphorylation of proteins of 150/145, 90, 42, and 35 kDa in cells from both age groups. Several growth factors were evaluated for their ability to stimulate early entry of adult satellite cells into the cell cycle, and none of the following growth factors were able to activate proliferation of these cells: FGF2, IGF-1, IGF-2, PDGF-BB, TGF-beta 1, or TGF-beta 2. In addition, specific binding of FGF2 to 48-h cultures of adult satellite cells was not stimulated by FGF2, IGF-1, IGF-2, PDGF-BB, or TGF-beta 2, and specific binding was significantly decreased (P < 0.05) by FGF2 and TGF-beta 2. Specific binding was significantly lower in cells treated with PDGF-BB than in cells treated with either form of IGF but was greater than in cells treated with FGF2 or TGF-beta 2. The results of these experiments suggest that expression of functional FGF receptors on the surface of satellite cells may represent an important step in the activation of quiescent satellite cells.
在培养的年轻（3至4周龄）和成年（9至12月龄）大鼠骨骼肌卫星细胞首次分裂前，评估了FGF2的特异性高亲和力结合。在接种后18小时，即最早检测时间，在年轻大鼠的卫星细胞上检测到FGF2的特异性结合，但在老年大鼠的卫星细胞上直到42小时才检测到特异性结合。这与成年卫星细胞进入细胞周期的延迟以及这些年龄段大鼠的卫星细胞对FGF2作出反应进行增殖的能力密切相关。FGF2刺激后，全细胞提取物中的酪氨酸磷酸化模式表明，两个年龄组细胞中150/145、90、42和35 kDa的蛋白质发生了特异性FGF2磷酸化。评估了几种生长因子刺激成年卫星细胞早期进入细胞周期的能力，以下生长因子均不能激活这些细胞的增殖：FGF2、IGF-1、IGF-2、PDGF-BB、TGF-β1或TGF-β2。此外，FGF2、IGF-1、IGF-2、PDGF-BB或TGF-β2均未刺激FGF2与成年卫星细胞48小时培养物的特异性结合，而FGF2和TGF-β2使特异性结合显著降低（P<0.05）。用PDGF-BB处理的细胞中的特异性结合显著低于用任何一种IGF处理的细胞，但高于用FGF2或TGF-β2处理的细胞。这些实验结果表明，卫星细胞表面功能性FGF受体的表达可能是静止卫星细胞激活的重要步骤。
