Henry J J, Mittleman J M
Department of Cell and Structural Biology, University of Illinois, Urbana 61801, USA.
Dev Biol. 1995 Sep;171(1):39-50. doi: 10.1006/dbio.1995.1258.
Previous studies have indicated that the outer cornea can undergo transdifferentiation to form a lens in the tadpole larva of Xenopus laevis following removal of the original lens. This transformation appears to require an interaction with the neural retina. In the present study, we carried out a series of experiments to determine if the matured tadpole eye can also elicit lens formation in embryonic ectoderm. Labeled embryonic ectoderm was removed from the presumptive lens-forming region, or from the belly region (ventral ectoderm), at various stages of development (stages 11-19, gastrula to neural tube stages) and implanted into the eye cavity (posterior chamber) of advanced stage 52-55 tadpoles. After 3 days, we examined the tadpoles and their implanted tissues for lens cell formation using lens-specific antibodies. Implanted presumptive lens ectoderm differentiated lens cells in a large number of cases. The percentage of cases forming lens cells and the extent of morphological differentiation increased with increasing age of the implanted tissue. Implanted ventral ectoderm also formed lens cells, although at a reduced frequency and with limited morphological differentiation. These results indicate that the environment of the matured tadpole eye cavity stimulates lens cell formation in both presumptive lens and nonlens ectoderm. The development of the implanted tissues was compared to that found in previous studies where these tissues were cultured as explants or transplanted to lens-forming regions during early development and subjected to various periods of embryonic lens induction. Together, these findings suggest that the process of embryonic lens formation is related to that involved in transdifferentiation of the tadpole cornea during "lens regeneration." However, the inductive effect of the matured tadpole eye is qualitatively different from that of the early period of embryonic lens induction and, while more intense, may be more closely related to that which takes place via the optic vesicle during the later phase of embryonic lens induction.
先前的研究表明，在非洲爪蟾的蝌蚪幼虫中，去除原始晶状体后，角膜外层可发生转分化形成晶状体。这种转变似乎需要与神经视网膜相互作用。在本研究中，我们进行了一系列实验，以确定成熟的蝌蚪眼是否也能诱导胚胎外胚层形成晶状体。在发育的各个阶段（第11 - 19阶段，原肠胚到神经管阶段），从假定的晶状体形成区域或腹部区域（腹侧外胚层）取出标记的胚胎外胚层，并植入晚期第52 - 55阶段蝌蚪的眼腔（后房）。3天后，我们使用晶状体特异性抗体检查蝌蚪及其植入组织中晶状体细胞的形成情况。在大量案例中，植入的假定晶状体外胚层分化出了晶状体细胞。形成晶状体细胞的案例百分比以及形态分化程度随着植入组织年龄的增加而增加。植入的腹侧外胚层也形成了晶状体细胞，尽管频率较低且形态分化有限。这些结果表明，成熟蝌蚪眼腔的环境刺激假定晶状体和非晶状体外胚层中晶状体细胞的形成。将植入组织的发育情况与先前研究中的情况进行了比较，在先前的研究中，这些组织作为外植体进行培养，或在早期发育期间移植到晶状体形成区域，并接受不同时期的胚胎晶状体诱导。总之，这些发现表明胚胎晶状体形成过程与蝌蚪角膜在“晶状体再生”期间的转分化过程有关。然而，成熟蝌蚪眼的诱导作用在性质上与胚胎晶状体诱导早期的作用不同，虽然更强，但可能与胚胎晶状体诱导后期通过视泡发生的作用更密切相关。
