Tooth replacement in an evo-devo context : the dental lamina as a possible source of stem cells

• Main Author: Vandenplas, Sam
• Other Authors: Huysseune, Ann, Witten, Paul Eckhard
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Ghent University. Faculty of Sciences 2016
• Subjects: Biology and Life Sciences; BrdU pulse chase labeling; stem cells; Tooth replacement; dental lamina; polyphyodont; Canicula; Salmo salar
• Online Access: https://biblio.ugent.be/publication/7138505; http://hdl.handle.net/1854/LU-7138505; https://biblio.ugent.be/publication/7138505/file/7138549

The enthralling ability to continuously replace teeth throughout life has fascinated scientists for decades. This ability (polyphyodonty) is maintained in almost all tooth-bearing non-mammalian vertebrates. Teeth are organised in tooth families, i.e. a functional tooth and all of its successors (Reif, 1982). In general, first and later generation teeth develop within an epithelial dental lamina as result of interaction of the epithelial cells with the underlying neural crest derived mesenchyme. Many aspects of tooth development and tooth evolution have been intensively studied over the past century; however the mechanism that drives lifelong tooth renewal remains largely unknown. Huysseune and Thesleff (2004) were the first to hypothesise that epithelial stem cells might be involved in this process, and suggested the dental lamina as a putative stem cell niche. In this thesis, we wished to test this hypothesis using a selection of polyphyodont species. In each of the species examined, we focussed on the lower jaw, and addressed three key issues: (1) the morphology and architecture of the dental tissues, with a particular interest for the dental lamina, (2) the spatiotemporal pattern of cell proliferation within the different layers of the dental lamina, and (3) the potential presence of epithelial stem cells. We selected three polyphyodont species that are interesting from a comparative, evo-devo perspective: a chondrichthyan (Scyliorhinus canicula) and two actinopterygian osteichthyans (Polypterus senegalus as a member of a basal clade within the Actinopterygii and Salmo salar as a basal protacanthopterygian). (1) Scyliorhinus canicula has many successor teeth, which are prefabricated before the functional tooth is shed (CHAPTER 3). This results in tooth family sizes of seven to eight members. All tooth families are interconnected by a continuous and permanent dental lamina and are organised in an alternating pattern of developmental stages along the jaw margin. Three to four members of each family reside in ...