Mitchell J J, Woodcock-Mitchell J L, Perry L, Zhao J, Low R B, Baldor L, Absher P M
Department of Physiology, University of Vermont, Burlington 05405-0068.
Am J Respir Cell Mol Biol. 1993 Jul;9(1):10-8. doi: 10.1165/ajrcmb/9.1.10.
alpha-Smooth muscle actin (alpha SM actin)-containing cells recently have been demonstrated in intraalveolar lesions in both rat and human tissues following lung injury. In order to develop model systems for the study of such cells, we examined cultured lung cell lines for this phenotype. The adult rat lung fibroblast-like "RL" cell lines were found to express alpha SM actin mRNA and protein and to organize this actin into stress fiber-like structures. Immunocytochemical staining of subclones of the RL87 line demonstrated the presence in the cultures of at least four cell phenotypes, one that fails to express alpha SM actin and three distinct morphologic types that do express alpha SM actin. The proportion of cellular actin that is the alpha-isoform was modulated by the culture conditions. RL cells growing at low density expressed minimal alpha SM actin. On reaching confluent densities, however, alpha SM actin increased to at least 20% of the total actin content. This effect, combined with the observation that the most immunoreactive cells were those that displayed overlapping cell processes in culture, suggests that cell-cell contact may be involved in actin isoform regulation in these cells. Similar to the response of some smooth muscle cell lines, alpha SM actin expression in RL cells also was promoted by conditions, e.g., maintenance in low serum medium, which minimize cell division. alpha SM actin expression was modulated in RL cells by the growth factor transforming growth factor-beta. Addition of this cytokine to growing cells substantially elevated the proportion of alpha SM actin protein.(ABSTRACT TRUNCATED AT 250 WORDS)
最近已证实在大鼠和人类肺损伤后的肺组织肺泡内病变中存在含α-平滑肌肌动蛋白（α-SM肌动蛋白）的细胞。为了建立用于研究此类细胞的模型系统，我们检测了培养的肺细胞系是否具有这种表型。发现成年大鼠肺成纤维细胞样“RL”细胞系表达α-SM肌动蛋白mRNA和蛋白，并将这种肌动蛋白组织成应力纤维样结构。RL87系亚克隆的免疫细胞化学染色显示培养物中至少存在四种细胞表型，一种不表达α-SM肌动蛋白，另外三种不同形态类型表达α-SM肌动蛋白。α-异构体形式的细胞肌动蛋白比例受培养条件调节。低密度生长的RL细胞表达极少的α-SM肌动蛋白。然而，达到汇合密度时，α-SM肌动蛋白增加至总肌动蛋白含量的至少20%。这一效应，再加上观察到免疫反应性最强的细胞是那些在培养中显示出重叠细胞突起的细胞，表明细胞间接触可能参与这些细胞中肌动蛋白异构体的调节。与一些平滑肌细胞系的反应相似，RL细胞中α-SM肌动蛋白的表达也受到如在低血清培养基中培养等条件的促进，这些条件可使细胞分裂减至最少。RL细胞中α-SM肌动蛋白的表达受生长因子转化生长因子-β调节。向生长中的细胞添加这种细胞因子可显著提高α-SM肌动蛋白的比例。（摘要截短至250字）
