Fuchigami Taro, Matsuzaki Takashi, Ihara Setsunosuke
Tottori University, Division of Resources Life Science, The United Graduate School of Agricultural Sciences, 4-101 Koyama-Minami, Tottori 680-8553, Japan.
Zoolog Sci. 2011 Sep;28(9):633-41. doi: 10.2108/zsj.28.633.
Wounds in Xenopus laevis embryos close rapidly, as previously described. In this study, we examined the dependence on extracellular Na(+) and/or Cl(-) ion concentrations of the closure of wounds in Xenopus embryos inflicted by thermal injury. Wound closure did not occur in normal amphibian medium (100% NAM), while wound areas remarkably decreased either in 10-50% NAM or in 100% NAM lacking Na(+) or Cl(-). Similarly, wound areas did not change in a set of Na(+) and Cl(-) ion concentrations equivalent to those of the humoral fluids of intact Xenopus embryos, but rapid wound closure was induced by decreasing the concentration of either of the two ions. A tangential accumulation of actin cytoskeleton along the wound edge was associated with wound closure. However, a similar actin alignment formed even under the 100% NAM condition, in which wounds did not close, as stated above. The epidermis around the wound edge exhibited ellipse-shaped hypertrophy, and the marginal cells centripetally elongated during wound closure. On the other hand, no distinct morphological changes occurred in 100% NAM, although the epidermis was somewhat thickened. Thus, the morphological changes in the epidermis specific to the low ionic environment most likely play active roles in the wound closure of Xenopus laevis embryos, whereas the tangential actin alignment alone may be insufficient. Taken together, we propose that the wound closure in Xenopus embryos is triggered by a decline in either the extracellular Na(+) or Cl(-) ion concentration, and that this process is required for the abovementioned changes in the shape of the marginal cells.
非洲爪蟾胚胎的伤口如先前所述会迅速愈合。在本研究中，我们检测了热损伤造成的非洲爪蟾胚胎伤口愈合对细胞外钠离子和/或氯离子浓度的依赖性。在正常两栖类培养基（100% NAM）中伤口不会愈合，而在10 - 50% NAM或缺乏钠离子或氯离子的100% NAM中，伤口面积显著减小。同样，在一组与完整非洲爪蟾胚胎体液中钠离子和氯离子浓度相当的条件下，伤口面积没有变化，但降低这两种离子中任何一种的浓度都会诱导伤口快速愈合。肌动蛋白细胞骨架沿伤口边缘的切向积累与伤口愈合相关。然而，如上文所述，即使在伤口不愈合的100% NAM条件下也会形成类似的肌动蛋白排列。伤口边缘周围的表皮呈现椭圆形肥大，并且在伤口愈合过程中边缘细胞向心伸长。另一方面，在100% NAM中虽然表皮有所增厚，但没有发生明显的形态变化。因此，低离子环境特有的表皮形态变化很可能在非洲爪蟾胚胎的伤口愈合中发挥积极作用，而仅靠切向肌动蛋白排列可能并不够。综上所述，我们提出非洲爪蟾胚胎的伤口愈合是由细胞外钠离子或氯离子浓度的下降触发的，并且这个过程对于上述边缘细胞形状的变化是必需的。
