Arresta Emiliano, Bernardini Sergio, Bernardini Enrico, Filoni Sergio, Cannata Stefano M
Dipartimento di Biologia, Università di Roma "Tor Vergata", I-00133 Rome, Italy.
J Exp Zool A Comp Exp Biol. 2005 Nov 1;303(11):958-67. doi: 10.1002/jez.a.219.
This study examines the retinal transdifferentiation (TD) of retinal pigmented epithelium (RPE) fragments dissected from Xenopus laevis larvae and implanted into the vitreous chamber of non-lentectomized host eyes. In these experimental conditions, most RPE implants transformed into polarized vesicles in which the side adjacent to the lens maintained the RPE phenotype, while the side adjacent to the host retina transformed into a laminar retina with the photoreceptor layer facing the cavity of the vesicle and with the ganglionar cell layer facing the host retina. The formation of a new retina with a laminar organization is the result of depigmentation, proliferation and differentiation of progenitor cells under the influence of inductive factors from the host retina. The phases of the TD process were followed using BrdU labelling as a marker of the proliferation phase and using a monoclonal antibody (mAbHP1) as a definitive indicator of retina formation. Pigmented RPE cells do not express Pax6. In the early phase of RPE to retinal TD, all depigmented and proliferating progenitor cells expressed Pax6. Changes in the Pax6 expression pattern became apparent in the early phase of differentiation, when Pax6 expression decreased in the presumptive outer nuclear layer (ONL) of the new-forming retina. Finally, during the late differentiation phase, the ONL, which contains photoreceptors, no longer expressed Pax6, Pax6 expression being confined to the ganglion cell layer and the inner nuclear layer. These results indicate that Pax6 may have different roles during the different phases of RPE to retinal TD, acting as an early retinal determinant and later directing progenitor cell fate.
本研究检测了从非洲爪蟾幼体解剖获得的视网膜色素上皮（RPE）碎片的视网膜转分化（TD），并将其植入未摘除晶状体的宿主眼的玻璃体腔中。在这些实验条件下，大多数RPE植入物转变为极化囊泡，其中与晶状体相邻的一侧维持RPE表型，而与宿主视网膜相邻的一侧转变为层状视网膜，其感光细胞层面向囊泡腔，神经节细胞层面向宿主视网膜。具有层状组织结构的新视网膜的形成是祖细胞在宿主视网膜诱导因子影响下发生色素脱失、增殖和分化的结果。使用BrdU标记作为增殖期的标志物，并使用单克隆抗体（mAbHP1）作为视网膜形成的确切指标，追踪TD过程的各个阶段。色素沉着的RPE细胞不表达Pax6。在RPE向视网膜TD的早期阶段，所有色素脱失且增殖的祖细胞均表达Pax6。当新形成视网膜的假定外核层（ONL）中Pax6表达降低时，Pax6表达模式的变化在分化早期变得明显。最后，在分化后期，包含感光细胞的ONL不再表达Pax6，Pax6表达局限于神经节细胞层和内核层。这些结果表明，Pax6在RPE向视网膜TD的不同阶段可能具有不同作用，在早期作为视网膜决定因素，后期指导祖细胞命运。
