Majors A K, Ehrhart L A
Department of Vascular Cell Biology and Atherosclerosis Research, Cleveland Clinic Foundation, Ohio 44195.
Exp Cell Res. 1992 May;200(1):168-74. doi: 10.1016/s0014-4827(05)80085-0.
Collagen synthesis and procollagen mRNA levels were determined and compared in (1) sparse, rapidly proliferating smooth muscle cells (SMC); (2) postconfluent, density-arrested SMC; and (3) sparse, nonproliferating (mitogen-deprived) rabbit arterial SMC. Collagen synthesis per SMC was decreased by 70% in postconfluent versus proliferating cells. However, relative collagen synthesis, expressed as the percentage of total protein synthesis, increased from 3.7% in sparse cultures to approximately 7% in postconfluent cultures. Slot blot analyses demonstrated that the relative steady state alpha 1(I) and alpha 1(III) procollagen mRNA levels were also increased in postconfluent cultures when compared to sparse cultures. As with collagen synthesis per cell, the mRNA levels per cell for types I and III procollagen in postconfluent cells, determined by densitometry of blots, were likewise approximately half that found in sparse, proliferating cells. In a separate study to determine if cell-cell contact was necessary for eliciting these changes in collagen synthesis, we determined collagen synthesis in mitogen-deprived and proliferating SMC cultures at low density. Mitogen-deprived cultures synthesized only 10% the amount of collagen produced (per cell) by proliferating cultures in 10% fetal bovine serum. Relative collagen synthesis in proliferating and nonproliferating cultures was 5.0 and 8.3%, respectively. These results demonstrate elevated collagen synthesis, per cell, by proliferating cultures compared with nonproliferating cultures, regardless of whether cells were rendered quiescent by density arrest or by mitogen deprivation. Results also suggest a pretranslational mechanism for the regulation of collagen synthesis in rabbit aortic smooth muscle cells.
在以下三种细胞中测定并比较了胶原蛋白合成及前胶原蛋白mRNA水平：（1）稀疏、快速增殖的平滑肌细胞（SMC）；（2）汇合后、密度抑制的SMC；（3）稀疏、不增殖（无丝裂原）的兔动脉SMC。与增殖细胞相比，汇合后细胞中每个SMC的胶原蛋白合成减少了70%。然而，以总蛋白合成的百分比表示的相对胶原蛋白合成，从稀疏培养物中的3.7%增加到汇合后培养物中的约7%。狭缝印迹分析表明，与稀疏培养物相比，汇合后培养物中相对稳态α1（I）和α1（III）前胶原蛋白mRNA水平也有所增加。与每个细胞的胶原蛋白合成情况一样，通过印迹密度测定法确定，汇合后细胞中I型和III型前胶原蛋白的每个细胞mRNA水平同样约为稀疏、增殖细胞中的一半。在另一项研究中，为了确定细胞间接触是否是引发胶原蛋白合成这些变化所必需的，我们在低密度下测定了无丝裂原和增殖的SMC培养物中的胶原蛋白合成。无丝裂原培养物合成的胶原蛋白量（每个细胞）仅为在10%胎牛血清中增殖培养物产生量的10%。增殖和不增殖培养物中的相对胶原蛋白合成分别为5.0%和8.3%。这些结果表明，与不增殖培养物相比，增殖培养物中每个细胞的胶原蛋白合成增加，无论细胞是通过密度抑制还是无丝裂原处理而进入静止状态。结果还提示了兔主动脉平滑肌细胞中胶原蛋白合成调控的转录前机制。
