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Enamel Organ (enamel + organ)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Growth of ameloblast-lineage cells in a three-dimensional Matrigel environment

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2006
Wu Li
Enamel organ epithelial cells grow in culture as two distinct cell populations , either stellate-shaped or polygonal-shaped cells. The polygonal cells have an ameloblast cell phenotype and are difficult to grow in culture beyond two passages. This study was designed to determine the effects of a Matrigel three-dimensional (3D) environment on polygonal cells, as compared with stellate cells, derived from porcine tooth enamel organ. Enamel organs were dissected free from the unerupted molars of 30-kg pigs and then grown in LCH-8e media, either with or without serum. Cells grown in serum-free media were primarily polygonal shaped, whereas cells grown in media containing serum were stellate shaped. Both types of cells were grown in a 3D Matrigel matrix. In addition, polygonal-shaped cells were mixed with hydroxyapatite powder and transplanted subcutaneously into nude mice. Polygonal-shaped epithelial cells formed cell groups, similar to epithelial pearls, both in vitro and in vivo. The stellate-shaped cells, in contrast, did not form similar structures, but remained suspended in the Matrigel and gradually disappeared from the culture. These results suggest that a Matrigel environment, rich in basement membrane and matrix proteins, selects for polygonal-shaped ameloblast-lineage cells and induces the formation of epithelial pearls. [source]

Effect of root surface treatment with propolis and fluoride in delayed tooth replantation in rats

DENTAL TRAUMATOLOGY, Issue 6 2008
Jéssica Lemos Gulinelli
Nevertheless, an extended extraoral period damages the periodontal ligament and results in external root resorption. The purpose of this study was to assess by histologic and histometric analysis, the influence of propolis 15% (natural resinous substance collected by Apis mellifera bees from various plants) and the fluoride solution used as root surface treatment on the healing process after delayed tooth replantation. Thirty Wistar (Rattus norvegicus albinus) rats were submitted to extraction of their upper right incisor. The teeth were maintained in a dry environment for 60 min. After this, the pulp was extirpated and the papilla, enamel organ and periodontal ligament were removed with scalpel. The teeth were divided into three experimental groups: Group I , teeth immersed in 20 ml of physiologic saline; Group II , teeth immersed in 20 ml of 2% acidulated phosphate sodium fluoride; Group III , teeth immersed in 20 ml of 15% propolis. After 10 min of immersion in the solutions, the root canals were dried and filled with calcium hydroxide paste and the teeth were replanted. The animals were euthanized 60 days after replantation. The results showed that similar external root resorption was seen in the propolis and fluoride groups. Teeth treated with physiologic saline tended to have more inflammatory root resorption compared with those treated with fluoride or propolis. However, the comparative analysis did not reveal statistically significant differences (P > 0.05) between the treatment modalities when used for delayed tooth replantation. [source]

Transforming growth factor-,1 expression is up-regulated in maturation-stage enamel organ and may induce ameloblast apoptosis

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2009
Masahiro Tsuchiya
Transforming growth factor-,1 (TGF-,1) regulates a variety of cellular responses that are dependent on the developmental stage and on the origins of the cell or the tissue. In mature tissues, and especially in tissues of epithelial origin, TGF-,1 is generally considered to be a growth inhibitor that may also promote apoptosis. The ameloblast cells of the enamel organ epithelium are adjacent to and responsible for the developing enamel layer on unerupted teeth. Once the enamel layer reaches its full thickness, the tall columnar secretory-stage ameloblasts shorten, and a portion of these maturation-stage ameloblasts become apoptotic. Here we investigate whether TGF-,1 plays a role in apoptosis of the maturation-stage ameloblasts. We demonstrate in vitro that ameloblast lineage cells are highly susceptible to TGF-,1-mediated growth arrest and are prone to TGF-,1-mediated cell death/apoptosis. We also demonstrate in vivo that TGF-,1 is expressed in the maturation-stage enamel organ at significantly higher levels than in the earlier secretory-stage enamel organ. This increased expression of TGF-,1 correlates with an increase in expression of the enamel organ immediate-early stress-response gene and with a decrease in the anti-apoptotic Bcl2 : Bax expression ratio. We conclude that TGF-,1 may play an important role in ameloblast apoptosis during the maturation stage of enamel development. [source]

Differentiation of human ameloblast-lineage cells in vitro

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2006
Qiaomei Yan
Previous studies have shown that ameloblast-like cells can be selectively cultured from the enamel organ in a serum-free medium with low calcium concentrations. The purpose of this study was to further characterize this culture system to identify differentiated ameloblast-lineage cells. Tooth organs from 19,24-wk-old fetal cadavers were either frozen and cryosectioned for immunostaining, or digested in collagenase/dispase for cell culture. The cells were grown in keratinocyte media supplemented with 0.05 mM calcium, and characterized by morphology and immunofluorescence. Epithelial clones with two distinct morphologies, including smaller cobblestone-shaped cells and larger (5,15 times in size) rounded cells, began to form between day 8 and day 12 after culture. The cobblestone-shaped cells continued to proliferate in culture, while the larger cells proliferated slowly or not at all. These larger cells formed filopodia, usually had two or more nuclei and a radiating cytoplasm at the cell margin, and were more abundant with increasing time in culture. Both cell types stained for cytokeratin 14, and the larger cells appeared more differentiated, showing stronger staining for amelogenin and ameloblastin. Immunofluorescence of the tooth bud sections showed staining for these matrix proteins as ameloblasts differentiated from the inner enamel epithelium. These results show the successful culture of differentiating ameloblast-lineage cells, and lay a foundation for use of these cells to further understand ameloblast biology with application to tooth enamel tissue engineering. [source]

Growth of ameloblast-lineage cells in a three-dimensional Matrigel environment

On the origin of intrinsic matrix of acellular extrinsic fiber cementum: Studies on growing cementum pearls of normal and bisphosphonate-affected guinea pig molars

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2002
Chantha K. Jayawardena
Cementum pearls (CPs) belong to a type of acellular extrinsic fiber cementum (AEFC) that form on the maturing enamel of guinea pig molars. This study aimed to elucidate the forming process of intrinsic matrix of AEFC using the CPs of normal and bisphosphonate-affected guinea pig molars as experimental models. A group of guinea pigs were subjected to continuous administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 2 wk to inhibit mineralization of growing CPs. Fenestration of the enamel organ and migration of periodontal cells on to the exposed surface of maturing enamel appeared to be unaffected by HEBP, whereas de novo formation as well as growth of pre-existing CPs did not proceed under the same conditions. Immunoreactions for osteopontin were located exclusively on the mineralized matrix of preformed CPs, implying the absence of additional deposition or accumulation of putative intrinsic cementum matrix on the affected CPs, where the propagation of mineral phase had been arrested. In both normal and HEBP-treated groups, distinct enzymatic reactions for alkaline phosphatase appeared on the cells of the periodontal ligament associated closely with the sites of CP formation, and along the mineralization front of CPs. These observations suggest that the mineralization process per se plays a central role in the deposition of AEFC matrix and that alkaline phosphatase of periodontal cells penetrating through the enamel organ to the maturing enamel surface plays a key role in the mineralization process of CPs. [source]

Technical advances in the sectioning of dental tissue and of on-section cross-linked collagen detection in mineralized teeth

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 8 2010
Sim K. Singhrao
Abstract Immunohistochemical detection of cross-linked fibrillar collagens in mineralized tissues is much desired for exploring the mechanisms of biomineralization in health and disease. Mineralized teeth are impossible to section when embedded in conventional media, thus limiting on-section characterization of matrix proteins by immunohistochemistry. We hypothesized that by using an especially formulated acrylic resin suitable for mineralized dental tissues, not only sectioning of teeth would be possible, but also our recently developed immunofluorescence labeling technique would be amenable to fully calcified tissues for characterization of dentinal fibrillar collagens, which remains elusive. The hypothesis was tested on fixed rodent teeth embedded in Technovit 9100 New®. It was possible to cut thin (1 ,m) sections of mineralized teeth, and immunofluorescence characterization of cross-linked type I fibrillar collagen was selected due to its abundance in dentine. Decalcified samples of teeth embedded in paraffin wax were also used to compare immunolabeling from either method using the same immunoreagents in equivalent concentrations. In the decalcified tissue sections, type I collagen labeling in the dentine along the tubules was "patchy" and the signal in the predentine was very weak. However, enhanced signal in mineralized samples with type I collagen was detected not only in the predentine but also at the limit between intertubular dentine, within the elements of the enamel organ and subgingival stroma. This report offers advances in sectioning mineralized dental tissues and allows the application of immunofluorescence not only for on-section protein detection but importantly for detecting cross-linked fibrous collagens in both soft and mineralized tissue sections. Microsc. Res. Tech. 73:741,745, 2010. © 2009 Wiley-Liss, Inc. [source]

Cytokeratins in epithelia of odontogenic neoplasms

ORAL DISEASES, Issue 1 2003
MM Crivelini
Neoplasms and tumours related to the odontogenic apparatus may be composed only of epithelial tissue or epithelial tissue associated with odontogenic ectomesenchyme. The immunohistochemical detection of different cytokeratins (CKs) polypeptides and vimentin has made it easier to explain the histogenesis of many epithelial diseases. The present study aimed to describe the immunohistochemical expression of cytokeratins 7, 8, 10, 13, 14, 18, 19 and vimentin in the epithelial components of the dental germ and of five types of odontogenic tumours. The results were compared and histogenesis discussed. All cells of the dental germ were positive for CK14, except for the preameloblasts and secreting ameloblasts, in which CK14 was gradually replaced by CK19. CK7 was especially expressed in the cells of the Hertwig root sheath and the stellate reticulum. The dental lamina was the only structure to express CK13. The reduced epithelium of the enamel organ contained CK14 and occasionally CK13. Cells similar to the stellate reticulum, present in the ameloblastoma and in the ameloblastic fibroma, were positive for CK13, which indicates a nature other than that of the stellate reticulum of the normal dental germ. The expression of CK14 and the ultrastructural aspects of the adenomatoid odontogenic tumour probably indicated its origin in the reduced dental epithelium. Calcifying odontogenic epithelial tumour is thought to be composed of primordial cells due to the expression of vimentin. Odontomas exhibited an immunohistochemical profile similar to that of the dental germ. In conclusion, the typical IF of odontogenic epithelium was CK14, while CK8, 10 and 18 were absent. Cytokeratins 13 and 19 labelled squamous differentiation or epithelial cells near the surface epithelium, and CK7 had variable expression. [source]