Kindy M S, Chang C J, Sonenshein G E
Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118.
J Biol Chem. 1988 Aug 15;263(23):11426-30.
Vascular smooth muscle cells produce the bulk of connective tissue protein in major arteries. Previously, we demonstrated that collagen synthesis by cultured bovine aortic smooth muscle cells in exponential growth is low and increases as cells approach confluence and growth slows. To evaluate more directly the effects of the proliferative state, subconfluent cultures of smooth muscle cells were incubated in medium supplemented with 0.5% fetal calf serum; under these conditions of growth factor deprivation, cells become quiescent within 72 h. The mRNA levels for type I and III collagens increased markedly within 12 h; at 48 h, they were between 2- and 15-fold higher than in cells growing exponentially. Upon addition of serum to quiescent cultures, cells re-entered the cycle, and collagen mRNA levels decreased. Expression of alpha 1(I), alpha 2(I), and alpha 1(III) mRNAs differed significantly, indicating differential gene regulation. In nuclear run-off assays, changes detected in collagen transcription were insufficient to account for changes in mRNA levels, suggesting additional post-transcriptional sites of control. The inverse response of collagen expression to the proliferative state suggests that exposure of smooth muscle cells in vivo to factors which influence their growth state could have profound effects on the structure of the arterial wall.
血管平滑肌细胞在大动脉中产生大部分结缔组织蛋白。此前，我们证明，处于指数生长期的培养牛主动脉平滑肌细胞的胶原蛋白合成量较低，随着细胞接近汇合且生长速度减慢，合成量会增加。为了更直接地评估增殖状态的影响，将亚汇合的平滑肌细胞培养物在补充有0.5%胎牛血清的培养基中孵育；在这些生长因子缺乏的条件下，细胞在72小时内进入静止状态。I型和III型胶原蛋白的mRNA水平在12小时内显著增加；在48小时时，它们比指数生长的细胞高出2至15倍。向静止培养物中添加血清后，细胞重新进入细胞周期，胶原蛋白mRNA水平下降。α1（I）、α2（I）和α1（III）mRNA的表达差异显著，表明存在差异基因调控。在核转录分析中，胶原蛋白转录中检测到的变化不足以解释mRNA水平的变化，这表明存在额外的转录后调控位点。胶原蛋白表达对增殖状态的反向反应表明，体内平滑肌细胞暴露于影响其生长状态的因素可能会对动脉壁结构产生深远影响。
