Immunohistochemical localization of syndecan-1 in the dental follicle of postnatal mouse teeth.

BACKGROUND: Syndecans are cell surface heparan sulfate proteoglycans that modulate the action of growth factors and extracellular matrix components. Syndecan-1 plays important roles during early tooth development, and it is expressed in the dental follicle of fetal tooth germ. However, no studies have followed its expression in the dental follicle during the postnatal period. We hypothesized that syndecan-1 protein expression in the dental follicle may be important for postnatal tooth development, and, thus, examined its expression patterns. METHODS: Syndecan-1 protein expression in the dental follicle of the lower first molar was investigated by immunohistochemistry using embryonic day (E) 18.5 to 21-day-old (d 21) mice. Immunoelectron microscopy was applied to the dental follicle and pulp cells to confirm its membrane localization in mesenchymal cells. RESULTS: Strong syndecan-1 immunostaining was maintained in the dental follicle and the adjacent dental pulp surrounded by the Hertwig's epithelial root sheath (HERS) from d 4 to d 14, but reduced staining was noted at d 21 with the near-completion of tooth eruption. Three dimensionally, syndecan-1-positive areas plugged the apical foramina surrounded by HERS. However, immunostaining was detected constantly in the dental follicle and the dental pulp of the lower incisor at d 21. In addition, membrane localization of syndecan-1 protein was confirmed for the first time in mesenchymal cells, including dental follicle and pulp cells, by immunoelectron microscopy. CONCLUSION: The spatial and temporal expression of syndecan-1 in the dental follicle suggests that this proteoglycan is important for the maintenance of proliferation and/or movement of cells in this region during tooth eruption.

Syndecan-1 expression during the formation of junctional epithelium.

BACKGROUND: Syndecans are cell surface heparan sulfate proteoglycans (PG) which can bind to and modulate the action of growth factors and extracellular matrix components (ECM). Syndecan- 1 has been shown to play important roles during early tooth development and wound healing and repair. Among diverse cells and tissues that comprise the periodontium, the junctional epithelium (JE) constitutes a region of significant anatomic and clinical importance, but the nature of inductive signals and molecules involved in its formation is still unclear. Therefore, this work examines if syndecan-1 is associated with formation of JE, and the distribution of other syndecan family members in the epithelium. METHODS: In situ hybridization and immunohistochemical techniques were performed using oral tissues from 4-day-old to 10-week-old mice to investigate the expression of syndecan- 1, -2, -3 and -4 mRNAs and their corresponding proteins. RESULTS: Based on in situ hybridization experiments, all syndecan mRNAs were detected in sulcular epithelium (SE), gingival epithelium (GE), and JE with varying intensity and distribution. Syndecan-1 immunostaining was localized on the cell surface while that of syndecan-2 did not show clear membrane localization. Our experiments in the developing tooth demonstrated that syndecan-1 protein followed characteristic patterns of expression during JE formation and that immunoreactivity for syndecan-1 protein decreased with age when JE cells underwent terminal differentiation. CONCLUSION: Results of syndecan-1 mRNA and protein expression patterns suggested that this proteoglycan might be an important molecule during the formation of JE.