Unsicker K
Dev Biol. 1985 Apr;108(2):259-68. doi: 10.1016/0012-1606(85)90030-2.
The morphological development and plasticity of embryonic and postnatal rat adrenal medullary cells were studied in homologous adrenal grafts to the anterior chamber of the eye. The eyes of recipient rats were adrenergically denervated 10 days prior to grafting by extirpation of the superior cervical ganglion in order to increase levels of NGF and NGF-like activities in the iris. Grafts taken at the 15th day of embryonic development (E15), i.e., at the beginning of immigration of medullary progenitor cells into the adrenal cortical anlagen, contained no cortical or mature medullary cells after 2 weeks in oculo. Numerous sympathoblastic cells, however, were located at the anterior surface of the iris. E 16 and E 17 transplants showed abundant mature cortical tissue after 2 weeks. Small groups of medullary cells with the ultrastructural characteristics of mature pheochromoblasts or young chromaffin cells were interspersed among cortical cells without forming a discrete medulla. Neuronal cells were exclusively found outside the cortical cell mass. Sympathoblasts grew at the surface of the iris, while young sympathetic nerve cells, which were invested by Schwann cells and received synaptic axon terminals, were embedded into the stroma of the iris. Grafting of E 21 adrenals yielded very similar results except that, in a few instances, young chromaffin cells were located outside the cortex and sympathetic nerve cells were seen to be in close contact with cortical cells. In transplants of adult medullary cells typical mature adrenaline and noradrenaline cells were clearly distinguishable after 8 weeks even in the absence of cortical cells. The only indication of phenotypical changes in these cells was the formation by some of them, of neuritic processes which could be visualized in glyoxylic acid-treated whole mounts of irises. These results are compatible with the idea that embryonic adrenal medullary cells have the environmentally controlled potential to develop along the neuronal or endocrine line, but could also be interpreted in terms of a selection of a specific subpopulation with predetermined potentialities by a specific microenvironment. Moreover, these results suggest that increasing differentiation of medullary cells is accompanied by progressive restrictions in their genetic program, which eventually prevent full transdifferentiation of mature chromaffin into neuronal cells.
通过将同源肾上腺移植到大鼠眼前房，对胚胎期和出生后大鼠肾上腺髓质细胞的形态发育和可塑性进行了研究。为了提高虹膜中神经生长因子（NGF）和NGF样活性水平，在移植前10天通过切除颈上神经节对受体大鼠的眼睛进行肾上腺素能去神经支配。取自胚胎发育第15天（E15）的移植物，即髓质祖细胞开始迁入肾上腺皮质原基时的移植物，在眼内放置2周后不含皮质细胞或成熟髓质细胞。然而，许多成神经细胞位于虹膜前表面。E16和E17移植物在2周后显示出丰富的成熟皮质组织。少数具有成熟嗜铬母细胞或年轻嗜铬细胞超微结构特征的髓质细胞散布在皮质细胞之间，未形成离散的髓质。神经元细胞仅在皮质细胞团块外发现。成神经细胞在虹膜表面生长，而被施万细胞包裹并接受突触轴突终末的年轻交感神经细胞则嵌入虹膜基质中。移植E21肾上腺产生了非常相似的结果，只是在少数情况下，年轻嗜铬细胞位于皮质外，并且可见交感神经细胞与皮质细胞紧密接触。在成年髓质细胞移植中，即使在没有皮质细胞的情况下，典型的成熟肾上腺素和去甲肾上腺素细胞在8周后也清晰可辨。这些细胞表型变化的唯一迹象是其中一些细胞形成了神经突，这在经乙醛酸处理的整个虹膜标本中可以观察到。这些结果与胚胎肾上腺髓质细胞具有受环境控制的沿神经元或内分泌谱系发育的潜能这一观点相符，但也可以从特定微环境选择具有预定潜能的特定亚群的角度来解释。此外，这些结果表明，髓质细胞分化的增加伴随着其基因程序的逐渐限制，最终阻止成熟嗜铬细胞完全转分化为神经元细胞。
