title: Light and electron microscopic studies of the intestinal epithelium in Notoplana humilis (Platyhelminthes, Polycladida): the contribution of mesodermal/gastrodermal neoblasts to intestinal regeneration.
abstract: Some free-living flatworms in the phylum Platyhelminthes possess strong regenerative capability that depends on putative pluripotent stem cells known as neoblasts. These neoblasts are defined based on several criteria, including their proliferative capacity and the presence of cellular components known as chromatoid bodies. Polyclads, which are marine flatworms, have the potential to be a good model system for stem cell research, yet little information is available regarding neoblasts and regeneration. In this study, transmission electron microscopy and immunostaining analyses, using antibodies against phospho-histone H3 and BrdU, were used to identify two populations of neoblasts in the polyclad Notoplana humilis: mesodermal neoblasts (located in the mesenchymal space) and gastrodermal neoblasts (located within the intestine, where granular club cells and phagocytic cells are also located). Light and electron microscopic analyses also suggested that phagocytic cells and mesodermal/gastrodermal neoblasts, but not granular club cells, migrated into blastemas and remodeled the intestine during regeneration. Therefore, we suggest that, in polyclads, intestinal regeneration is accomplished by mechanisms underlying both morphallaxis (remodeling of pre-existing tissues) and epimorphosis (de novo tissue formation derived from mesodermal/gastrodermal neoblasts). Based on the assumption that gastrodermal neoblasts, which are derived from mesodermal neoblasts, are intestinal stem cells, we propose a model to study intestinal regeneration.
authors.affiliation: Department of Biology, Faculty of Agriculture and Life Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori, 036-8561, Japan. okano@hirosaki-u.ac.jp.|The United Graduate School of Agricultural Sciences, Iwate University, 3-18-8 Ueda, Morioka, 020-8550, Japan. okano@hirosaki-u.ac.jp.
authors.forename: Daisuke
authors.identifier: http://orcid.org/0000-0001-8307-4790
authors.initials: D
authors.lastname: Okano
authors.affiliation: Department of Biology, Faculty of Agriculture and Life Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori, 036-8561, Japan.|The United Graduate School of Agricultural Sciences, Iwate University, 3-18-8 Ueda, Morioka, 020-8550, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Ishida
authors.affiliation: Department of Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori, 036-8561, Japan.
authors.forename: Sei-ichi
authors.initials: S
authors.lastname: Ishiguro
authors.affiliation: Department of Biology, Faculty of Agriculture and Life Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori, 036-8561, Japan.|The United Graduate School of Agricultural Sciences, Iwate University, 3-18-8 Ueda, Morioka, 020-8550, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002465:Cell Movement; D049109:Cell Proliferation; D048430:Cell Shape; D004847:Epithelial Cells / Q000166:cytology / Q000648:ultrastructure; D007413:Intestinal Mucosa / Q000033:anatomy & histology / Q000166:cytology* / Q000648:ultrastructure*; D008648:Mesoderm / Q000166:cytology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D008938:Mitosis; D010932:Planarians / Q000166:cytology* / Q000648:ultrastructure*; D012038:Regeneration; D013194:Staining and Labeling
keywords: Chromatoid body; Intestinal regeneration; Neoblasts; Polyclads (Polycladida); Stem cells