Boumediene K, Félisaz N, Pujol J P
Laboratoire de Biochimie du Tissu Conjonctif, Facultéde Médecine, Caen Cedex, 14032, France.
Exp Cell Res. 1998 Aug 25;243(1):173-84. doi: 10.1006/excr.1998.4129.
We previously found that transforming growth factor beta type 1 (TGFbeta1) had bifunctional effects on articular chondrocytes in culture depending on the proliferative state of the cells. Here, TGFbeta1 responses and the expression of TGFbeta receptors I and II were investigated as a function of growth state in rabbit articular chondrocytes (RAC) and Mv1Lu cells, a cell line which is growth inhibited by TGFbeta1. In contrast to these latter cells, in which DNA synthesis was decreased by TGFbeta1 independently of the cell cycle phases, exponentially growing RAC responded with a stimulation of DNA synthesis while confluent or quiescent cells were growth inhibited. Using synchronized RAC cultures, we showed that inhibitory responses were associated with the G0/G1 phase, whereas proliferative effects were S-phase dependent. Type I receptor mRNA level was severalfold greater in quiescent and slowly proliferating than in exponentially growing cells. In contrast, the expression of type II mRNA did not change. 125I-TGFbeta1 binding to RI in G0/G1-arrested cells was greater than in S-phase, suggesting a correlation with the growth-inhibitory effect of TGFbeta1. Transfection of an RI expression vector in exponentially growing RAC, which normally are growth stimulated by TGFbeta1, induced an inhibitory response, supporting the idea that this effect was due to increased RI expression. These results indicate that the ratio of type I to type II levels is cell cycle dependent and could lead to either negative or positive proliferative responses. In contrast, no influence on the TGFbeta1-induced stimulation of matrix gene transcriptional activity was seen, confirming that TGFbeta cell growth and matrix effects are controlled by separate pathways.
我们先前发现，转化生长因子β1（TGFβ1）对培养的关节软骨细胞具有双相作用，这取决于细胞的增殖状态。在此，我们研究了兔关节软骨细胞（RAC）和Mv1Lu细胞（一种受TGFβ1抑制生长的细胞系）中TGFβ1的反应以及TGFβ受体I和II的表达与生长状态的关系。与后一种细胞不同，在后者中TGFβ1可使DNA合成减少，且与细胞周期阶段无关，而指数生长的RAC对TGFβ1的反应是DNA合成受到刺激，而汇合或静止的细胞则生长受到抑制。利用同步化的RAC培养物，我们发现抑制性反应与G0/G1期相关，而增殖作用则依赖于S期。静止和缓慢增殖的细胞中I型受体mRNA水平比指数生长的细胞高几倍。相比之下，II型mRNA的表达没有变化。在G0/G1期停滞的细胞中，125I-TGFβ1与RI的结合比S期更强，这表明与TGFβ1的生长抑制作用相关。在指数生长的RAC中（其通常受TGFβ1刺激生长）转染RI表达载体可诱导抑制性反应，这支持了该效应是由于RI表达增加的观点。这些结果表明I型与II型水平的比例是细胞周期依赖性的，并且可能导致负性或正性增殖反应。相比之下，未观察到对TGFβ1诱导的基质基因转录活性刺激的影响，这证实了TGFβ对细胞生长和基质的作用是由不同途径控制的。
