Hofmann H D, Seidl K, Unsicker K
Max-Planck-Institut for Brain Research, Frankfurt, Federal Republic of Germany.
J Electron Microsc Tech. 1989 Aug;12(4):397-407. doi: 10.1002/jemt.1060120412.
Neural crest derived precursors of the sympathoadrenal cell lineage give rise to two major cell types that differ in a number of morphological, ultrastructural, and biochemical characteristics: principal sympathetic neurons and chromaffin cells of the adrenal medulla. The present article reviews experimental studies performed on cultured adrenal medullary cells and designed to unravel the nature of epigenetic signals governing the developmental choice between the endocrine chromaffin and the neuronal sympathetic phenotype. Emphasis is placed on the role of glucocorticoids in initiation, development, and maintenance of the endocrine chromaffin phenotype and apparently antagonistic influences exerted by nerve growth factor (NGF) in vitro, resulting in the acquisition of neuronal properties by differentiated chromaffin cells. Experimental data from in vitro studies are compatible with the following conclusions. Glucocorticoids represent the decisive signal for the initial induction of endocrine differentiation. Moreover, high steroid hormone concentrations, as present in the adrenal medulla, are a prerequisite for the maturation of chromaffin cells. Even in a differentiated state, the endocrine phenotype is unstable in the absence of glucocorticoids, and the cells seem to reenter the neuronal developmental pathway. Under these conditions, cellular survival and differentiation into sympathetic neurons become NGF-dependent, as in normal sympathetic development. Thus, the effects of NGF survival, neurite outgrowth, and transmitter synthesis of cultured chromaffin cells probably do not reflect the induction of a specific phenotype, but they may be interpreted as a general neurotrophic support observable with other responsive cell types.
神经嵴衍生的交感肾上腺细胞谱系前体产生两种主要细胞类型，它们在许多形态、超微结构和生化特征上存在差异：主要的交感神经元和肾上腺髓质的嗜铬细胞。本文综述了对培养的肾上腺髓质细胞进行的实验研究，这些研究旨在揭示调控内分泌嗜铬细胞和神经元交感表型之间发育选择的表观遗传信号的本质。重点阐述了糖皮质激素在启动、发展和维持内分泌嗜铬细胞表型中的作用，以及神经生长因子（NGF）在体外产生的明显拮抗作用，导致分化的嗜铬细胞获得神经元特性。体外研究的实验数据与以下结论相符。糖皮质激素是内分泌分化初始诱导的决定性信号。此外，肾上腺髓质中存在的高浓度甾体激素是嗜铬细胞成熟的先决条件。即使处于分化状态，在没有糖皮质激素的情况下，内分泌表型也是不稳定的，细胞似乎会重新进入神经元发育途径。在这些条件下，细胞存活和分化为交感神经元变得依赖NGF，就像在正常交感神经发育中一样。因此，NGF对培养的嗜铬细胞的存活、神经突生长和递质合成的影响可能并不反映特定表型的诱导，但它们可以被解释为与其他反应性细胞类型一样可观察到的一般神经营养支持。
