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S Vainio

Publications and source records attributed to S Vainio.

42 records · Page 3Linked to original sources
PubMed1989

Cell-matrix interactions in tooth development.

A chain of reciprocal interactions between the epithelial and mesenchymal tissues regulates both morphogenesis and cell differentiation in the developing tooth. The very early interactions lead to budding of the oral epithelium and to the characteristic condensation of the neural crest-derived mesenchymal cells around the epithelial bud. During the bell stage of morphogenesis, the mesenchymal cells which are in contact with the dental epithelium differentiate into odontoblasts. In this reveiw article we summarize the results of our descriptive and experimental studies, which indicate that differentiation of the dental mesenchymal cells into odontoblasts, as well the condensation of dental mesenchymal cells at the bud stage, are regulated by interactions between the cell surface and the extracellular matrix. Transfilter studies where the dental epithelium and mesenchyme were cultured on opposite sides of Nuclepore filters, led to the hypothesis that the differentiation of dental mesenchymal cells into odontoblasts is triggered by interactions between the cell surface and the epithelial basement membrane matrix. Immunohistochemical localization of various matrix molecules showed that the matrix glycoproteins fibronectin and tenascin are accumulated in the dental basement membrane at the time of odontoblast differentiation. Fibronectin and tenascin are known to interact with each other, with other matrix molecules as well as with the cell surface, and also to influence cell shape. We suggest that fibronectin and tenascin are involved in the cell-matrix interaction which leads to the polarization and differentiation of odontoblasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Cell surface proteoglycan expression correlates with epithelial-mesenchymal interaction during tooth morphogenesis.

Tooth morphogenesis and differentiation of the dental cells are guided by interactions between epithelial and mesenchymal tissues. Because the extracellular matrix is involved in these interactions, the expression of matrix receptors located at the cell surface may change during this developmental sequence. We have examined the distribution of an epithelial cell surface proteoglycan antigen, known to behave as a receptor for interstitial matrix, during tooth morphogenesis. Intense staining was seen around the cells of the embryonic oral epithelium as well as the dental epithelium at the early bud stage. With development, expression was greatly reduced in the enamel organ. Differentiation of these cells into ameloblasts was associated with the loss of expression, while the epithelial cells remaining in the stratum intermedium and stellate reticulum regained intense staining. The PG antigen was weakly expressed in the loose neural crest-derived jaw mesenchyme but it became strongly reactive in the condensed dental papilla mesenchyme when extensive morphogenetic movements took place. With development, the PG antigen disappeared from the advanced dental papilla mesenchyme but persisted in the dental sac mesenchyme, which gives rise to periodontal tissues. The PG antigen was not expressed by odontoblasts. Hence, the expression of the PG antigen changes during the epithelial-mesenchymal interactions of tooth development and is lost during terminal cell differentiation. The expression follows morphogenetic rather than histologic boundaries. The acquisition and loss of expression in epithelial and mesenchymal tissues during tooth development suggest that this proteoglycan has specific functions in the epithelial-mesenchymal interactions that guide morphogenesis.

Animals↗
PubMed1988

Production of monoclonal antibodies against murine dental papilla.

The mesenchymal component of the embryonic tooth, the dental papilla, shows unique cellular behavior. Only the dental papilla cells are capable of differentiating into odontoblasts. The dental papilla also directs the morphogenesis of the tooth. Our aim is to develop suitable markers for further studies on the molecular mechanisms behind the determination and differentiation of the dental mesenchymal cells. We have produced monoclonal antibodies against this embryonal cell population. Altogether 1114 enzymatically separated mesenchymes from dissected molar tooth germs of 17-day-old mouse embryos were fixed in paraformaldehyde (PFA) and sonicated in saline. A rat was immunized and hybridomas were produced by standard methods. The supernatants were screened by immunohistology, using both frozen sections and sections of PFA-fixed paraffin-embedded mouse molar teeth. Altogether, 19 wells produced antibodies reacting with dental tissues. One monoclonal antibody recognizes a 67,000 dalton intracellular antigen enriched in secretory odontoblasts and ameloblasts. The antigen is also found in osteoblasts and chondrocytes in the developing jaw, and in some cultured murine cells. The method described here appears to be successful for generating and screening monoclonal antibodies against the dental papilla.

Ameloblasts↗
PubMed1987

Changes in the distribution of tenascin during tooth development.

Tenascin is an extracellular matrix molecule that was earlier shown to be enriched in embryonic mesenchyme surrounding the budding epithelium in various organs including the tooth. In the present study tenascin was localized by immunohistology throughout the course of tooth development in the mouse and rat using polyclonal antibodies against chick tenascin. The results indicate that tenascin is expressed by the lineage of dental mesenchymal cells throughout tooth ontogeny. The intensity of staining with tenascin antibodies in the dental papilla mesenchyme was temporarily reduced at cap stage when the tooth grows rapidly and undergoes extensive morphogenetic changes. During the bell stage of morphogenesis, the staining intensity increased and tenascin was accumulated in the dental pulp even after completion of crown development and eruption. Tenascin was present in the dental basement membrane at the time of odontoblast differentiation. The dental papilla cells ceased to express tenascin upon differentiation into odontoblasts and tenascin was completely absent from dentin. It can be speculated that the remarkable expression of tenascin in the dental mesenchymal cells as compared to other connective tissues is associated with their capacity to differentiate into hard-tissue-forming cells.

Animals↗
PubMedDate not supplied

Epithelial-mesenchymal interactions in tooth morphogenesis: the roles of extracellular matrix, growth factors, and cell surface receptors.

Morphogenesis and cell differentiation in the developing tooth are controlled by a series of reciprocal interactions between the epithelial and mesenchymal tissues. The exact molecular mechanisms operating in these interactions are unknown at present, but both structural components of the extracellular matrix (ECM) and diffusible growth factors have been suggested to be involved. In this review article we summarize our findings on the distribution patterns of three ECM molecules and two cell surface receptors during tooth morphogenesis through bud, cap, and bell stages of development. The examined molecules include fibronectin, type III collagen, and tenascin, which all represent components of the mesenchymal ECM, the cell surface proteoglycan, syndecan, which functions as a receptor for interstitial matrix, and the cell surface receptor for epidermal growth factor. Based on the observed changes in distribution patterns and on experimental evidence, roles are suggested for these molecules in epithelial-mesenchymal interactions during tooth development. Fibronectin is suggested to be involved in the cell-matrix interaction that controls odontoblast differentiation. Epidermal growth factor and its receptors are suggested to be involved in a paracrine fashion in the epithelial-mesenchymal interactions regulating morphogenesis of bud- and cap-stage teeth. Tenascin and syndecan are accumulated in the dental mesenchyme during the bud stage of development, and it is suggested that they represent a couple of a cell surface receptor and its matrix ligand and that they are involved in mesenchymal cell condensation during the earliest stages of tooth morphogenesis.

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