Department of Genetics, University of Barcelona, Av, Diagonal 643, edifici annex, planta 2a, 08028 Barcelona, Spain.
Front Zool. 2013 Oct 28;10(1):64. doi: 10.1186/1742-9994-10-64.
Regeneration is a widespread phenomenon in the animal kingdom, but the capacity to restore damaged or missing tissue varies greatly between different phyla and even within the same phylum. However, the distantly related Acoelomorpha and Platyhelminthes share a strikingly similar stem-cell system and regenerative capacity. Therefore, comparing the underlying mechanisms in these two phyla paves the way for an increased understanding of the evolution of this developmental process.To date, Isodiametra pulchra is the most promising candidate as a model for the Acoelomorpha, as it reproduces steadily under laboratory conditions and is amenable to various techniques, including the silencing of gene expression by RNAi. In order to provide an essential framework for future studies, we report the succession of regeneration events via the use of cytochemical, histological and microscopy techniques, and specify the total number of cells in adult individuals.
Isodiametra pulchra is not capable of regenerating a new head, but completely restores all posterior structures within 10 days. Following amputation, the wound closes via the contraction of local muscle fibres and an extension of the dorsal epidermis. Subsequently, stem cells and differentiating cells invade the wound area and form a loosely delimited blastema. After two days, the posterior end is re-patterned with the male (and occasionally the female) genital primordium being apparent. Successively, these primordia differentiate into complete copulatory organs. The size of the body and also of the male and female copulatory organs, as well as the distance between the copulatory organs, progressively increase and by nine days copulation is possible. Adult individuals with an average length of 670 μm consist of approximately 8100 cells.
Isodiametra pulchra regenerates through a combination of morphallactic and epimorphic processes. Existing structures are "re-modelled" and provide a framework onto which newly differentiating cells are added. Growth proceeds through the intercalary addition of structures, mirroring the embryonic and post-embryonic development of various organ systems. The suitability of Isodiametra pulchra for laboratory techniques, the fact that its transcriptome and genome data will soon be available, as well as its small size and low number of cells, make it a prime candidate subject for research into the cellular mechanisms that underlie regeneration in acoelomorphs.
再生是动物界普遍存在的现象，但不同门之间以及同一门内的组织损伤或缺失的修复能力差异很大。然而，亲缘关系较远的无腔动物门和扁形动物门却拥有惊人相似的干细胞系统和再生能力。因此，比较这两个门的潜在机制为深入了解这一发育过程的进化提供了可能。迄今为止，美丽多棘虫是研究无腔动物门的最佳候选模型，因为它在实验室条件下稳定繁殖，并且可采用包括 RNAi 在内的各种技术来沉默基因表达。为了为未来的研究提供重要框架，我们通过使用细胞化学、组织学和显微镜技术报告了再生事件的顺序，并确定了成年个体中的细胞总数。
美丽多棘虫不能再生新的头部，但在 10 天内完全恢复所有的尾部结构。截肢后，伤口通过局部肌肉纤维的收缩和背表皮的延伸而闭合。随后，干细胞和分化细胞侵入伤口区域并形成一个界限松散的胚基。两天后，尾部重新形成雄性（偶尔也形成雌性）生殖器原基。随后，这些原基分化成完整的交配器官。身体的大小以及雄性和雌性交配器官的大小，以及交配器官之间的距离逐渐增加，到第九天就可以交配了。平均长度为 670 μm 的成年个体由大约 8100 个细胞组成。
美丽多棘虫通过形态发生和胚胎发生的结合进行再生。现有的结构被“重新塑造”，并提供了一个新分化细胞添加的框架。生长通过结构的间插添加进行，反映了各种器官系统的胚胎和胚胎后发育。美丽多棘虫适合实验室技术，其转录组和基因组数据即将可用，以及它的体型小、细胞数量少，使其成为研究无腔动物门再生的细胞机制的理想候选对象。
