Relationship Between Vestibular Lamina, Dental Lami and the Developing Oral Vestibule in the Upper Jaw of the Field Vole (Microtus agrestis, Rodentia) Kirsti Witter, 1 * Hana Pavlikova, 2 Petra Matulova, 3 and Ivan Misek 2,3 1 Institute of Histology and Embryology, Department of Pathobiology, University of Veterinary Medicine Vienna, A-1210 Vienna, Austria 2 Institute of Anatomy, Histology and Embryology, University of Veterinary and Pharmaceutical Sciences Brno, CZ-612 42 Brno, Czech Republic 3 Laboratory of Genetics and Embryology, Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, CZ-602 00 Brno, Czech Republic ABSTRACT Formation of the oral vestibule is ignored in most studies on tooth development, although dental and vestibular lamina are closely related to each other. Knowl- edge about morphogenetic processes shaping the oral ves- tibule is missing almost completely. The aim of this study was to assess the developmentalrelationship between dental and vestibular lamina as well as formation of the oral vestibule in the upper jaw of the field vole (Microtus agrestis), a small rodent representing an attractive model species for comparative dental studies. Three-dimensional reconstruction revealed that the upper vestibular lamina of the vole joins the antemolar part of the diastemal dental lamina, similar to mouse. Later, this lamina complex re- gresses and the vestibular lamina is separated from the molar epithelium.Participation of the vestibular lamina in dental lamina formation,as hypothesized for mouse, therefore remains unclear. Except for increased apoptosis in the regressing diastemal dental lamina, spatial segre- gation of mitoses or apoptoses could be detected neither in the jaw arch epithelium nor in the adjacent mesenchyme. Therefore,in contrast to tooth primordia,apoptosis and mitosis seem to play a minor role in shaping of the upper oral vestibule. The buccal vestibule develops secondarily, probably in consequence of general growth of the head and localized differentiation of cells. J. Morphol. 265:264 –270, 2005. © 2005 Wiley-Liss, Inc. KEY WORDS: mouth; dentition; tooth; prenatal develop- ment; morphogenesis; odontogenesis The vestibular lamina is an epithelial lamina im- mersed in the jaw arch mesenchyme. It represents the primordium of the oral vestibule, the space be- tween teeth and gums on one side and lips and cheeks on the other side, at least in the anterior part of the mouth (Pouchet and Chabry, 1884; Bild, 1902; Peterkova, 1985; Pavlikova et al., 1999). The vesti- bular lamina of the mouse derives, together with the dental lamina, from a common epithelial placode— the odontogenic epithelialzone (Peterkova,1985; Peterkova et al., 2002). Although vestibular lamina and dental lamina are developmentally closely related and the murine ves- tibular lamina has been hypothesized to participate in molar development (Peterkova et al., 2002),the vestibular lamina is mostly ignored in odontogenetic studies. Except for mouse (e.g., Peterkova, 1985; Peterkova et al., 2002), sheep (Pavlikova et al., 1999), and man (Hovorakova et al., 2005), there is no recent information on vestibular lamina develop- ment at all. Vestibular lamina, dental lamina, and palatal ridge primordia of mouse segregate atembryonic day (E) 11.5–12.0 (Peterkova, 1985; Peterkova et al., 2002), probably by mesenchymal bulging or swelling (Peterkova et al., 2002). Morphogenetic processes leading to this in- and outfolding have not been studied so far. Localized proliferation and apoptotic cell death could cause shape changes in this region, as known for morphogenesis of tooth primordia (e.g., Lesot et al., 1996). The field vole, Microtus agrestis, is a small rodent with the same tooth formula (1.0.0.3/1.0.0.3) and a similar anatomical structure of the mouth as mouse. However, tooth shape and tooth development differ between mouse and vole (Witter et al., 2005). These differences and the possibility to use experimental approaches developed for mouse (Kera¨ nen et al., 1998,1999;Jernvall et al., 2000; Matulova et al., Contract grant sponsor: Grant Agency of the Czech Republic; Con- tract grant number: 304/02/0448; Contract grant sponsor: Ministry of Education,Youth and Sports of the Czech Republic; Contract grant number: COST project OC B23.001. *Correspondence to: Kirsti Witter, Institute of Histology and Em- bryology, University of Veterinary Medicine Vienna, Veterina¨ rplatz 1, A-1210 Wien, Austria. E-mail: Kirsti.Witter@vu-wien.ac.at Published online 15 July 2005 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/jmor.10356 JOURNAL OF MORPHOLOGY 265:264–270 (2005) ©2005 WILEY-LISS, INC.