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Early morphogenesis of dentition in humans
Hovořáková, Mária
In humans, the deciduous dentition develops from the U-shaped dental lamina running along the upper or lower jaw arch. It is assumed that the vestibular lamina is located externally and parallel to the dental lamina and gives rise to the oral vestibule. We investigated the early development of the dentition and the oral vestibule from embryonic week 6 to 9 by using serial frontal histological sections and computer-aided 3D reconstructions. The thickened dental epithelium originated separately on the medial nasal, maxillary and mandibular outgrowths before their fusion. After complete fusion, the dental epithelium formed a continuous mound in 3D reconstructions, giving rise to single tooth primordia. Externally to the dental mound, we regularly observed epithelial structures on frontal sections, protruding into the mesenchyme. Without correlation with 3D reconstructions, these structures could be considered as forming a continuous U-shaped vestibular lamina. However, 3D reconstructions did not show any continuous vestibular lamina. At the earlier fusion site of the dental epithelia of the upper jaw, the lateral deciduous incisor started to develop, comprising material from both: medial nasal and maxillary outgrowths. We can conclude that the continuous vestibular lamina does not exist. The...
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The role of rudimentary structures in odontogenesis.
Lochovská, Kateřina ; Hovořáková, Mária (advisor) ; Buchtová, Marcela (referee) ; Štembírek, Jan (referee)
In vivo organogenesis is based on the temporal-spatial developmental processes that depend on cell behaviour, for example on their growth, migration, differentiation and intercellular interactions. Such behaviour is regulated by appropriate transient expression of various signalling molecules. Despite the significant advances in therapeutic strategies, the secret of the development of the biological replacement of a damaged or missing tooth has not yet been revealed. In this context, animal models provide a powerful tool for studying tooth normogenesis and pathogenesis in both basic and applied research. Early development of the tooth shares similar morphological and molecular features with other ectodermal organs. At the same time, these features are largely preserved also between species, which is advantageous for the use of model organisms. The dental formula of both: the human and the mouse are reduced against a common ancestor, but both groups of organisms evince simple as well as multicusped teeth. In both, structures called rudimentary were found. These structures are suppressed during ontogenetic development and generally they are not attributed to essential functions. That is why we aimed to study dental rudiments in detail and reveal their function in odontogenesis. This work presents new...
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The signs of odontogenesis externally to the prospective functional dentition in the experimental model
Fábik, Jaroslav ; Hovořáková, Mária (advisor) ; Buchtová, Marcela (referee)
6 Abstract The development of the mouse tooth primordium is an important model for studying odontogenesis, as well as general organogenesis. The development of the mouse lower incisor is of remarkable interest. The epithelial anlage of the mouse lower incisor is interconnected with the vestibular anlage via the epithelial bridges. According to some authors, the epithelial bridges represent an area, where the transient rudimentary incisor germ appears. From a morphological point of view, the first sign of ongoing epithelial-mesenchymal interactions during early odontogenesis is the thickening of oral epithelium. From a molecular point of view, it is the expression of the Shh, Eda, Edar, Pitx2, Bmp2, Bmp4 and Dlx2 genes. Except for the transcription domain, representing the proper signalling centre of a developing prospective incisor, a transient transcription domain, localized anteriorly and superficially, appears in the odontogenic zone of the epithelium during early development. The anterior transcription domain originates in the area of epithelial bridges, and according to some authors, from an evolutionary point of view, it corresponds with the signalling centre of the rudimentary incisor germ. The aim of this diploma thesis was to compare the temporospatial dynamics of SHH and EDA protein expression in...
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Birth weight of newborns with orofacial clefts
Hofmannová, Oldřiška ; Hovořáková, Mária (advisor) ; Buchtová, Marcela (referee)
Orofacial clefts are frequent congenital anomalies. A combination of genetic and environmental factors contributes to their formation. Orofacial clefts together with growth retardation belong among the indicators of embryo toxicity. This thesis is focused on the potential relationship between birth weight and orofacial clefts of newborns born in Czech Republic. The non-syndromic cleft lip, cleft lip and palate, isolated cleft palate and patients with Pierre-Robin sequence are discussed here. Evaluation of the relationship between the birth weight and orofacial clefts was performed on the base of statistical analysis. The differences were tested in children with different types of orofacial clefts and in cleft patients compared to healthy control. Statistical analysis of variance demonstrated that the type and severity of the cleft (unilateral/ bilateral) does not affect birth weight of newborns with orofacial clefts. Newborns with non-syndromic clefts had reduced birth weight in comparison to healthy controls. Cleft patients with Pierre-Robin sequence (syndromic form of cleft) did not differ in birth weight from healthy children. To verify the results obtained in patients with orofacial clefts that the birth weight is lower in these patients compared to control, two experiments on a chicken model...
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Developmental and structural analysis of similarities among calcified and keratinized tooth structures in mouth of vertebrates
Karpecká, Zuzana ; Černý, Robert (advisor) ; Hovořáková, Mária (referee)
Calcified teeth comprise the hardest vertebrate tissues (enamel and dentine) and they undoubtedly represent a key evolutionary advantage for their users. Nevertheless, teeth have been lost many times and they were often replaced by keratinised structures, such as rhamphoteca of birds or of turtle beaks, or labial tooth structures and scratching laminae of many aquatic vertebrates. This thesis is intended to analyse levels of similarities among keratinised teeth and structures of three phylogenetically distinct lineages of amniotes and to compare them to morphogenesis of true teeth. Detailed developmental and structural characteristics of oral apparatus possessing keratinous teeth of lampreys, Loricarid cathfishes and frog tadpoles were identified and distinguished. Keratinous structures of cathfishes include only horny projections from single cell surface (unculi), whereas in frog tadpoles both horny jaw sheet and unicellular labial teeth composed by cell columns were found; the lamprey oral apparatus consists of multicellular teeth and laminae instead. Disparate phenotypes of these keratinous structures can, however, developmentally derive from a general process of keratinization: morphological disparities arise by distinct gradual accretion of keratinous layers and collumns during development. My...
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Tracing the fate of cell populations from regressive tooth primordia during ontogenesis
Řadová, Marie ; Hovořáková, Mária (advisor) ; Černý, Jan (referee)
(v anglickém jazyce) Development of tooth primordia in mice is an important model for study of odontogenesis. Several dental rudiments develop during the mouse embryogenesis. These structures develop in functional teeth in their phylogenetically older relatives. Similarly, we can initiate growth of teeth from these germs in some mutant mice. In my diploma thesis we have focused on the importance of rudimentary structures with odontogenic potential in postnatal individuals. As a model of development, we have chosen a cell population originating from rudimentary primordia MS (mesial segment) that develops in diastema of the lower jaw during the embryonic day 12.5. Using the inducible Cre-lox technology we have marked the cells which are part of the signal domain of primordia at this time. As a marker of these cells we have used gene Shh. We have found out that these cells persist prenataly and also postnatally. Further we have isolated this cell area and we have tested it using a variety of methods. We have shown that in the cells of postnatal individual are expressed markers of stem cells (Sox2, Bmi1, Gli1) and also genes for major enamel matrix structural proteins: ameloblastin and amelogenin. The same stem cell markers are also expressed in vitro culture of the isolated cells. This cell population...
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Formation of human dental anomalies in odontogenesis of mouse models with gene defects.
Lochovská, Kateřina ; Hovořáková, Mária (advisor) ; Peterka, Miroslav (referee)
Laboratory mouse is a appropriate experimental model for studies on normal tooth development mechanisms and for understanding of etio-pathogenesis of dental anomalies in humans. Mouse dentition consists of one incisor separated from three molars by toothless diastema in each jaw quadrant. Although an adult mice diastema does not contain teeth, rudimentary tooth primordia (MS, R2) appear here during embryonic development. However, their development stops and consequently functional tooth does not arise here. It is known that in mice with mutations in Spry2 and Spry4 genes, supernumerary teeth arise in antemolar region. The understanding of the temporo-spatial dynamics of signaling centers in Spry2/Spry4 double transgenic mice may help to elucidate the role of these embryonic diastemal buds in supernumerary tooth formation. The research of possible regeneration of dental anomalies in off-spring of crossing Spry4 deficient mice with supernumerary teeth formation with Eda deficient mice with predisposition to reduced dentition could be the way to elucidating of mechanism of dental pathologies development in general. Our aim was to describe temporal and spatial dynamics of Shh signaling domains in Spry2/Spry4 embryos, because Shh is one of the markers of early odontogenesis and determining of...
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Analysis of embryotoxic effect of hydrocortisone using chick embryotoxicity screening test (CHEST).
Janíková, Michaela ; Peterka, Miroslav (advisor) ; Hovořáková, Mária (referee)
Cleft lip is one of the most common human birth deffects. Its etiopathogenesis is multifactorial and many aspects of its occurrence remain unknown in the fields of both genetics and teratology. One of the set of known negative external factors causing cleft lip is chemical hydrocortisone. Its effect on cell proliferation is highly heterogeneous and depends on attributes of a specific cell population. In this work we studied the cleft beak origin after the hydrocortisone treatment on the basis of Chick Embryotoxicity Screening Test (CHEST). Our main aim was to detect cell cycle changes in the chick frontonasal process after hydrocortisone injection via flow cytometry analysis. Hydrocortisone caused S phase arrest within a minor subpopulation of highly granular cells with specific cell cycle. This sensitive subpopulation was localized in the areas of previously defined proliferative centers within the frontonasal process using immunohistochemistry of frozen sections. Quantitative analysis of cells in these areas revealed significant decrease of M phase portion in the hydrocortisone treated samples in comparison with the control samples. The TUNEL staining of histological sections was used to determine the apoptotic rate in the frontonasal process. The comparison between the control and the...
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Morphological variability of the incisor in mutant mice
Lochovská, Kateřina ; Churavá, Svatava (referee) ; Hovořáková, Mária (advisor)
Myš je nejfrekventovaněji používaným experimentálním modelovým organismem pro studium vývoje zubů. Myší funkční dentice obsahuje jeden řezák oddělený od tří molárů dlouhou bezzubou diastemou v každém čelistním kvadrantu. Cílem této práce bylo shrnout poznatky o myší dentici a jejím vývoji se zaměřením na myší řezáky a jejich patologie. Myší řezák je díky svým vlastnostem jedinečným zubem. Charakteristickou vlastností hlodavců jsou právě kontinuálně rostoucí řezáky. Tyto řezáky jsou pokryté sklovinou pouze na labiální straně. Lingvální povrch je tvořen pouze dentinem. Toto je spojeno s asymetrickou abrazí. Nicméně je také častým cílem mutací, ať už v podobě delece nebo jiné modifikace genů. Tyto mutace dentálních signálních drah jsou studovány na mutantních myších jako jsou například Tabby myši, Sprouty nebo Small eye (Sey) mutantní myši a mnoho dalších. Některé mutace jsou homologní k lidským onemocněním. Například X-vázaný tabby (Ta) syndrom u myší je považován za homolog hypohidrotické ektodermální dysplásie (HED) u lidí. Tato mutace napadá velikost řezáku, jeho tvar a pozici stejně jako cytodiferenciaci. Dále se může objevit hypodoncie, anodoncie nebo nějaké morfologické změny napadající ostatní existující zuby. Abnormality v počtu, velikosti a tvaru zubu byly dobře zdokumentovány v lidské...
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