Thesis (doctoral)--Umeå Universitet, Sweden, 1989. / Extra t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 2004. / Includes bibliographical references.

Thesis (M. Sc.)--McGill University, 1995. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M. Sc.)--McGill University, 1995. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Family with sequence similarity 20 (FAM20) consists of three members: FAM20A, FAM20B and FAM20C. Mutations in FAM20 family have been linked to developmental disorders involving bones, cartilage and teeth. FAM20A mutations in humans are associated with amelogenesis imperfecta with gingival fibromatosis and enamel renal syndrome. Fam20a knockout (KO) mouse showed growth retardation. The aim of this study was to characterize the skeletal and dental phenotypes using Fam20a KO mouse. Our results showed that body size and bone length of KO mice were smaller than those of WT. The microcomputed tomography (μCT) analyses of trabecular and cortical bones in KO displayed lower bone volume, thinner trabeculae and thinner bone cortex as compared to WT. Histological examination of KO growth plate demonstrated disorganized chondrocyte zones and extended hypertrophic zone. qRT-PCR results showed downregulation of several osteoblast differentiation markers in KO long bone. Immunohistochemical examination demonstrated reduced chondrocyte proliferation, apoptosis and increased collagen X expression in KO growth plate. Our data showed a lower number of osteoblasts and osteoclasts in KO as compared to WT. In vitro study, Fam20a KO showed a lower number of bone marrow stromal cells and osteoprogenitors. In vitro mineralization was impaired in KO osteoblasts. Fam20a KO had hypoplastic enamel, delayed tooth eruption and gingival overgrowth. The µCT results demonstrated that enamel in Fam20a KO was not fully mineralized and enamel matrix was detached from dentin. Scanning electron microscopy displayed absence of decussation patterns in Fam20a KO enamel. Histological examination of maxillary first molar at differentiation stage showed no difference between WT and KO. At the secretory stage, Fam20a KO ameloblasts were short and non-polarized as compared to WT. Immunohistochemical analysis showed diffuse staining pattern of amelogenin in Fam20a KO first molar compared to WT. Western blot analysis demonstrated that amelogenin proteolytic process was impaired in KO and showed slower migration pattern of MMP20. In conclusion, endochondral ossification defects and reduced number of osteoblasts and their precursors led to the bone phenotype in Fam20a KO. Amelogenin processing defects caused amelogenesis imperfecta phenotype in KO. Our study indicated that Fam20a plays a role in skeletal development and amelogenesis.

Amelogenesis imperfecta (AI) is a genetically determined enamel defect characterized by genetic and clinical heterogeneity . The prevalence and incidence of AI were established in the county of Västerbotten, northern Sweden, in 3-19-yr-olds born 1963-79, as were the mode of inheritance and clinical manifestation of AI. The distribution of the inorganic component in the enamel of AI teeth was studied as well as the surface morphology and other morphological details, and the findings were correlated to genetic and clinical data. AI was diagnosed in 79 children and adolescents (index cases). The prevalence in the study population was 1.4: 1 000. The mean yearly incidence 1963-79 was 1.3:1 000. The inheritance patterns for AI were established in 78 index cases from 51 families. Pedigree and segregation analyses suggested autosomal dominant (AD) inheritance in 3 3 families, autosomal recessive (AR) in six families, and X- linked recessive in two families; in ten families only sporadic cases were found. In one of the families with an AD inheritance pattern, X-linked dominant was a possible alternative. Examination of the families of the 78 index cases revealed 107 new cases of AI. The hypoplastic form was seen in 72% of all diagnosed cases and the hypomineralization form in 28% of the cases. A further classification of the clinical manifestations led to the identification of eight clinical variants. In 3 3 of the 51 families the same clinical variant was found in all affected members. In eight families affected members were assigned to different clinical variants. In three families with an X-linked inheritance pattern for AI, the clinical manifestation differed between women and men due to lyo- nization. Among the remaining five families, with an AD inheritance pattern for AI, variants clinically characterized by hypoplasia as well as variants characterized by hypomineralization were found in three families; in the other two families the clinical manifestation varied within the same main form of AI, i.e. hypoplasia or hypomineralization. Hypoplasia as well as hypomineralization were observed microradiographically in the enamel of most of the examined teeth. These findings were supported by scanning electron microscopy (SEM). Both clinically and microradiographically as well as by SEM, similar variants of AI were found as AD and AR traits and/or among the sporadic cases. In the families with AI as an X-linked trait the genetic hypothesis was confirmed by the clinical, microradiographic and scanning electron microscopic findings. / <p>S. 1-46: sammanfattning, s. 47-134: 5 uppsatser</p> / digitalisering@umu

Orientador: Sergio Roberto Peres Line / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-15T10:58:03Z (GMT). No. of bitstreams: 1 Mofatto_LucianaSouto_M.pdf: 6634624 bytes, checksum: a7a375b605c9d038d37a20e654d5333a (MD5) Previous issue date: 2010 / Resumo: A fluorose dentária é caracterizada por manchas no esmalte dentário devido a hipomineralização causada pela ingestão crônica de flúor durante o desenvolvimento dos dentes. O flúor parece interferir diretamente na formação da matriz do esmalte dentário. Estudos demonstraram que a matriz orgânica do esmalte dentário na fase secretória é birrefringente quando analisada em microscopia de luz polarizada, demonstrando que esta matriz possui uma ordenação supramolecular e que alterações genéticas e ambientais que afetam a estrutura do esmalte também afetam a organização supramolecular da matriz orgânica do esmalte dentário. Neste trabalho foi proposto analisar o efeito do flúor na maturação e organização supramolecular da matriz em linhagens de camundongos A/J, CBA e DBA/2 que possuem diferentes suscetibilidades à fluorose e sua associação com níveis sistêmicos de flúor no plasma, nos ossos e na urina. O efeito do flúor na matriz orgânica do esmalte dentário foi estudado através das análises de birrefringência e de absorbância de cortes histológicos corados com Ponceau SS. Noventa e seis camundongos (32 da linhagem A/J, 33 da linhagem CBA e 31 da linhagem DBA/2) foram aleatoriamente divididos em três grupos (0, 11.25 e 45 ppm de flúor adicionados à água de beber) e submetidos a um tratamento de 49 dias. O método do eletrodo específico foi usado para determinar as concentrações de flúor nos ossos, plasma e urina. Foram utilizadas: microscopia de polarização para analisar a birrefringência da matriz orgânica do esmalte e microscopia de luz para determinar a absorbância desta matriz. Como resultado, foi observado menor efeito do flúor na birrefringência no grupo 11.25 ppmF da linhagem A/J. Também nesta linhagem foram notadas maiores alterações de tonalidade no esmalte maduro nos grupos 11.25 e 45 ppmF. Entretanto, as maiores concentrações de flúor nos ossos e no plasma foram encontradas nos animais da linhagem DBA/2 tratados com 11.25 e 45 ppmF. O flúor não causou alteração na quantidade de proteína da matriz do esmalte durante a fase secretória. Conclusão: A linhagem mais suscetível a fluorose dentária foi a A/J, devido às alterações mais evidentes no esmalte maduro. No entanto, a matriz orgânica do esmalte na fase secretória foi menos afetada nesta linhagem do que nas demais. O flúor promoveu uma alteração na organização supramolecular da matriz orgânica do esmalte dentário na fase secretória, visto que este composto causou uma diminuição na birrefringência sem ocasionar uma redução significativa na quantidade de proteínas presentes na matriz. A linhagem A/J, mesmo sendo a mais suscetível à fluorose dentária, apresentou menores concentrações plasmática e óssea de flúor / Abstract: Dental fluorosis is characterized by alterations in the aspect of mature enamel due to hypomineralization, it is caused by chronic ingestion of fluoride during tooth development. Fluoride seems to influence on formation of enamel organic matrix. Previous studies have shown that the organic extracellular matrix of the enamel secretory phase is birefringent, evidencing the presence of an ordered supramolecular structure, and that the birefringence can be altered by genetical and environmental factors that also affect mature enamel. The aim of this work was to analyse the effect of fluoride on the matrix maturation and supramolecular organization in A/J, CBA and DBA/2 mice strains and its association to fluoride systemic levels in plasma, bones and urine. There are different patterns of susceptibility to fluorosis among these strains. The effect of fluoride on enamel organic matrix was studied by birefringence and absorbance analysis of Ponceau SS stained sections. Ninety six mice (32 A/J strain, 33 CBA strain and 31 DBA/2 strain) were randomly distributed in three groups (0, 11.25 and 45 ppm of fluoride in drinking water) submitted to a 49-days treatment. Fluoride levels in bones, plasma and urine were determined by F specific electrode. Polarizing microscopy was used to analyse the birefringence of enamel organic matrix and light microscopy was used to determinate the matrix absorbance. As result, 11.25 ppmF group of A/J strain showed least effect of fluoride on birefringence. Colouring alterations were observed in the mature enamel on 11.25 and 45 ppmF groups of A/J strain. However, 11.25 and 45 ppmF groups of DBA/2 strain presented highest levels of fluoride in bones and plasma. Fluoride did not change the protein amount of enamel matrix during secretion stage. Conclusion: A/J strain was the most susceptible to dental fluorosis because it showed more alterations in the mature enamel. However, enamel organic matrix of A/J strain was the least affected during the secretion phase. Fluoride promoted a change in the supramolecular organization of enamel organic matrix during the secretion stage. This compound caused a birefringence decrease without causing a significant reduction on matrix protein amount. A/J strain, even being the most susceptible to dental fluorosis, showed the lowest levels of fluoride in plasma and bones / Mestrado / Histologia e Embriologia / Mestre em Biologia Buco-Dental

Healthy tooth formation is crucially dependent on normal development of enamel and dentin. Any deviation from norm could lead to serious effects on the teeth function. Amelogenesis Imperfecta (AI) and Dentinogenesis Imperfecta (DGI) are genetically inherited conditions that affect the teeth formation. Thus is imperative to investigate the genes and proteins that contribute to these conditions. Some of the known proteins that play a role in amelogenesis include AMELOGENIN (AMLEX), KALLIKREIN 4(KLK4), FAMILY WITH SEQUENCE SIMILARITY 83H (FAM83H), WD REPEAT-CONTAINING PROTEIN 72 (WDR72) and DENTIN SIALOPHSOPHPROTEIN (DSPP). The purpose of this research project was to investigate the expression/localization pattern of gene products which are known to be causative for Amelogenesis Imperfecta and Dentinogenesis Imperfecta.The study was carried out using mouse heads which were fixed, demineralized and paraffin-embedded. Samples were then sectioned and immunohistochemical analysis was performed with various enamel/dentin protein antibodies. The data showed the following results: KLK4 showed immunoreactivity mainly in ameloblasts and in the pulp, DSPP showed immunoreactivity in dentin, in the pulp and in the epithelial cells on one location as indicated by the arrow in figure 3 of the tooth cross section, FAM83H has a faint immunoreactivity identified in the ameloblasts, WDR72 showed weak immunoreactivity in the ameloblasts and AMELX showed immunoreactivity on the enamel and the ameloblasts. In conclusion these findings were supported by previous studies and conveyed the validity of IHC experiments in locating these proteins in odontogenic tissues.

The tribosphenic molar is an ancestral type of mammalian teeth and a phy- lotypic stage of the mammalian dental evolution. Yet, in contrast to derived teeth types, its enamel microarchitecture attracted only little attention and the information on that subject is often restricted to statements suggesting a simple homogenous arrangement of a primitive radial prismatic enamel. The present paper tests this prediction with aid of comparative study of eight model species representing the orders Chiroptera, Afrosoricida, Eulipotyphla (Erinaceomorpha) and Eulipotyphla (Soricomorpha). Spe- cial attention was paid to shrews (Soricidae), the group with most derived tribosphenic dentition among extant insectivores. The detailed electron microscopic (SEM) analysis of standardized cross sections over essential structural elements of tribosphenic molars (in shrews supplemented with sections of the lower incisor, the most derived tooth of the dentition) was a basic source of information. The results demonstrated common arrangements related to tribosphenic design (he- terotopy of enamel thickness, radial prismatic enamels as primary product of ameloge- netic activity), yet, an unexpectedly broad span of variation in state of further variables was discovered at the same time. The taxon-specific arrangements and...

L'émail dentaire est la couche de tissu externe calcifié recouvrant la couronne de la dent; c’est la structure la plus minéralisée du corps humain. L'émail est synthétisé par l’améloblaste au cours du développement de la dent, mais cette population cellulaire dégénère et régresse totalement lorsque la dent devient fonctionnelle. L'émail mature est donc complètement dépourvu de cellules et de contenu protéique. L’amélogénine, la principale protéine de l’émail a la capacité de s’assembler en structures très organisées de type nanochaînes qui vont guider et réguler les cristaux d’hydroxyapatite de l’émail en formation. Le Leucine Rich Amelogenin Peptide (LRAP) est un produit de l'épissage alternatif du gène de l'amélogénine ; c’est un peptide court (56kDa), composée des séquences actives et N- et C-terminales de la protéine d’amélogénine complète. Dans ce travail, nous avons cherché à comprendre le rôle de LRAP dans l’amélogenèse. Nous avons montré 1) que LRAP présentait les mêmes propriétés d’auto-assemblage que la forme complète d’amélogénine et ses produits de clivage ; 2) que LRAP possédait les même propriétés de régulation des phosphates de calcium que la protéine complète ; et 3) que la conformation de la forme phosphorylée de LRAP était modifiée par une augmentation de la concentration de calcium dans le milieu environnant contrairement à la forme déphosphorylée de LRAP. Dans un second temps, nous avons étudié les propriétés de signalisation du peptide et confirmé nos résultats de minéralisation sur des modèles de culture de cellules de type améloblastique LS8 et ALC in vitro et sur un modèle de culture de germe de première molaire de souris ex vivo. Nous avons montré que la présence des deux formes de LRAP, active la cinétique de différenciation des cellules LS8 et ALC in vitro et favorise la formation de cristaux d’HAP organisés et allongés. Dans les germes en culture, la présence de LRAP(+P) dans un milieu minéralisant permet une augmentation de la densité et du volume de minéral formé alors que dans un milieu standard, il favorise la différenciation des germes. LRAP(-P) entraine en revanche, la synthèse par les améloblastes sécréteurs de longs et fins cristaux d’HAP bien organisés. Ce travail pourrait ouvrir de nouvelles stratégies de régénération des tissus de l'émail afin de traiter des altérations de la couche d'émail résultant de lésions carieuses à l’aide du LRAP(-P) ou de troubles génétiques comme l’amélogenèse imparfaite en utilisant plutôt le LRAP(+P). / Tooth enamel is the outer calcified layer covering the crown of the tooth; it is the most mineralized tissue of the human body. Enamel is synthesized by ameloblast during tooth development, but this cell population degenerates and regresses when the tooth becomes fully functional. The mature enamel is completely devoid of cells and protein content. The amelogenin, the main protein of the enamel has the ability to assemble into highly organized nanochains, which will guide and regulate the deposition of hydroxyapatite crystals during enamel formation. The Leucine Rich Amelogenin Peptide (LRAP) is a product of alternative splicing of the amelogenin gene; it is a short peptide (56kDa), composed of the active N- and C-terminal sequences of the complete amelogenin protein. The aim of this work is to understand is to understand the role of LRAP in enamel formation. We have shown 1) that LRAP presents the same self-assembling properties as the full-length form of amelogenin and its cleavage products; 2) that LRAP exhibits the same calcium phosphate regulating properties as the full-length protein; and 3) that the conformation of the phosphorylated form of LRAP was modified by increasing concentration of calcium in the surrounding medium unlike the dephosphorylated form of LRAP. In the second part of this work, we have studied the peptide signaling properties and confirmed our mineralization results on ameloblast lineage cell culture models (LS8 and ALC) in vitro and on mice first molar germ culture model ex vivo. We have shown that the presence of both forms of LRAP activate the kinetic of differentiation of LS8 and ALC cells in vitro, and results in the formation of organized elongated HAP crystals. In the germ culture experiments, addition of LRAP(+P) in a mineralizing medium induces an increase in the density and volume of the mineral formed whereas in the standard medium, it promotes differentiation of the germs. LRAP(-P) leads to the synthesis by secretory ameloblasts of well organized long and fine HAP crystals. This work may lead the way toward new strategies for enamel tissue regeneration in order to treat alterations in the enamel layer resulting from carious lesions with the LRAP(-P) or genetic disorders such as amelogenesis imperfecta using LRAP(+P).