Hornsby P J, Yang L Q
Department of Cell and Molecular Biology, Medical College of Georgia, Augusta 30912.
Mech Ageing Dev. 1991 Apr 1;58(1):1-12. doi: 10.1016/0047-6374(91)90115-g.
We have developed a cell model for loss of differentiated gene expression in cellular aging. Over long periods in culture, bovine adrenocortical cells lose expression of a specialized gene, steroid 17 alpha-hydroxylase. The decline in expression of 17 alpha-hydroxylase in mass cultures and clones of bovine adrenocortical cells is the result of a phenotypic switching process which yields a mixture of cells that can express 17 alpha-hydroxylase after induction with cyclic AMP and cells that are incapable of expression of 17 alpha-hydroxylase. In the experimental portion of the work, bovine adrenocortical cells were grown in culture in colonies, stimulated with cyclic AMP to induce 17 alpha-hydroxylase, then fixed and hybridized in situ with labeled 17 alpha-hydroxylase cDNA. Separate images of Giemsa-stained cell colonies and of their hybridization patterns were digitized and combined as stylized representations of the colonies for comparison with those produced by a computer simulation. A program for the simulation of growth of colonies of bovine adrenocortical cells in senescence with phenotypic switching of 17 alpha-hydroxylase is presented. Comparison between simulated colonies and real colonies shows that the model accurately simulates colony growth and phenotypic switching. It suggests that the probability of phenotypic switching per cell generation is in the range of 0.03 to 0.06. The major variable among colonies is division probability, consistent with observations in this and other cell culture systems that clones differ widely in replicative potential. Thus, phenotypic switching of 17 alpha-hydroxylase in adrenocortical cells may be modelled using simple assumptions.
我们已经建立了一个细胞衰老过程中分化基因表达丧失的细胞模型。在长期培养过程中，牛肾上腺皮质细胞会丧失一种特殊基因——类固醇17α-羟化酶的表达。在牛肾上腺皮质细胞的大规模培养物和克隆中，17α-羟化酶表达的下降是一个表型转换过程的结果，该过程产生了两种细胞的混合物，一种是在用环磷酸腺苷诱导后能够表达17α-羟化酶的细胞，另一种是无法表达17α-羟化酶的细胞。在这项工作的实验部分，将牛肾上腺皮质细胞在培养皿中培养成集落，用环磷酸腺苷刺激以诱导17α-羟化酶，然后固定并用标记的17α-羟化酶cDNA进行原位杂交。将吉姆萨染色的细胞集落及其杂交模式的单独图像进行数字化处理，并组合成集落的程式化表示，以便与计算机模拟产生的图像进行比较。本文提出了一个用于模拟牛肾上腺皮质细胞衰老集落生长以及17α-羟化酶表型转换的程序。模拟集落与真实集落之间的比较表明，该模型能够准确模拟集落生长和表型转换。这表明每个细胞世代发生表型转换的概率在0.03至0.06之间。集落之间的主要变量是分裂概率，这与在这个以及其他细胞培养系统中的观察结果一致，即克隆的复制潜力差异很大。因此，可以使用简单的假设对肾上腺皮质细胞中17α-羟化酶的表型转换进行建模。
