CELL-CYCLE VERSUS DENSITY DEPENDENCE OF SMOOTH-MUSCLE ALPHA-ACTIN EXPRESSION IN CULTURED RAT AORTIC SMOOTH-MUSCLE CELLS
CELL-CYCLE VERSUS DENSITY DEPENDENCE OF SMOOTH-MUSCLE ALPHA-ACTIN EXPRESSION IN CULTURED RAT AORTIC SMOOTH-MUSCLE CELLS
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DOI：
10.1083/jcb.107.1.299
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发表时间：
1988-07-01
影响因子：
7.8
通讯作者：
OWENS, GK
中科院分区：
文献类型：
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作者：
BLANK, RS;THOMPSON, MM;OWENS, GK
培养的平滑肌细胞（SMC）在融合时经历平滑肌（SM）α肌动蛋白的诱导。由于汇合细胞表现出接触抑制生长，这一发现表明，SM α肌动蛋白的诱导可能与细胞周期的撤退。在本研究中，进一步研究了这个问题，使用荧光激活细胞分选的SMC进行诱导融合和检查的影响，FBS和血小板衍生生长因子（PDGF）对SM α肌动蛋白表达融合后SMC培养物，已经经历了诱导。细胞分选基于DNA含量或溴脱氧尿苷（Budr）的差异掺入。融合细胞中SM α肌动蛋白的合成分数比亚融合对数期细胞增加2 - 3倍，但融合循环（Budr+）和非循环（Budr-）细胞之间没有观察到差异。在未暴露于Budr的培养物中，汇合的循环S + G2细胞表现出类似的诱导。这些数据表明，细胞周期的撤回是不是一个先决条件的诱导SM α肌动蛋白合成SMC融合。融合后培养物与FBS或PDGF的生长刺激导致SM α肌动蛋白合成的显著抑制，但抑制水平与进入S期没有直接关系，因为PDGF是比FBS更有效的SM α肌动蛋白合成抑制剂，尽管促有丝分裂作用较小。FBS与PDGF的这种差异效应似乎不是由于转化生长因子β对PDGF诱导的抑制没有影响。同样，FBS（0.1-10.0%）不能抑制PDGF诱导的抑制。综上所述，这些数据表明，复制频率以外的因素支配培养的SMC的分化，并表明，一个重要的功能，如PDGF的有效的生长因子可能是肌肉特异性的特点的镇压。
Cultured smooth muscle cells (SMC) in undergo induction of smooth muscle (SM) alpha actin at confluency. Since confluent cells exhibit contact inhibition of growth, this finding suggests that induction of SM alpha actin may be associated with cell cycle withdrawal. This issue was further examined in the present study using fluorescence-activated cell sorting of SMC undergoing induction at confluency and by examination of the effects of FBS and platelet-derived growth factor (PDGF) on SM alpha actin expression in postconfluent SMC cultures that had already undergone induction. Cell sorting was based on DNA content or differential incorporation of bromodeoxyuridine (Budr). The fractional synthesis of SM alpha actin in confluent cells was increased two- to threefold compared with subconfluent log phase cells, but no differences were observed between confluent cycling (Budr+) and noncycling (Budr-) cells. In cultures not exposed to Budr, confluent cycling S + G2 cells exhibited similar induction. These data indicate that cell cycle withdrawal was not a prerequisite for the induction of SM alpha actin synthesis in SMC at confluency. Growth sitmulation of postconfluent cultures with either FBS or PDGF resulted in marked repression of SM alpha actin synthesis but the level of repression was not directly related to entry into S phase in that PDGF was a more potent repressor of SM alpha actin synthesis than was FBS despite a lesser mitogenic effect. This differential effect of FBS versus PDGF did not appear to be due to transforming growth factor-beta had no effect on PDGF-induced repression. Likewise, FBS (0.1-10.0%) failed to inhibit PDGF-induced repression. Taken together these data demonstrate that factors other than replicative frequency govern differentiation of cultured SMC and suggest that an important function of potent growth factors such as PDGF may be the repression of muscle-specific characteristics.