[Effect of epidermal growth factor on transcription of MCP-1 in rat dental follicle cells].

PURPOSE: To study the effects of epidermal growth factor (EGF) on the secretion of monocyte chemotactic protein-one (MCP-1) in rat dental follicle cells. METHODS: Dental follicle was harvested from 4-6 days postnatal Wistar rats and cultured in alpha-MEM with 15% FBS. Cells in the third passage were incubated with EGF at different concentrations to choose the best dosage. MTT assays were used to evaluate cell proliferation. Using the suitable concentration, 10 ng/ml EGF cells were cultured for 0, 0.5, 1, 3 and 6 hours respectively, and then collected for RT-PCR analysis. The results were analyzed with SPSS13.0 software package. RESULTS: EGF(ng/ml) at 5-10 ng/ml increased the cell proliferation (P<0.05), which reached the peak at 10 ng/ml according to MTT assay (P<0.01). 10 ng/ml and 3 hours EGF exposure up-regulated the cellular MCP-1 expression dramatically (P<0.01). CONCLUSION: Proper concentration of EGF may promote dental follicle cell proliferation, EGF may up-regulate MCP-1 transcription in the rat dental follicle cells.

[Hertwig's epithelial root sheath, bone matrix proteins, and initiation of cementogenesis in mouse teeth].

PURPOSE: The aim of this study was to analyze the association between Hertwig's epithelial root sheath (HERS), noncollagenous matrix proteins, and cementogenesis. METHODS: Eighteen BALB/c postnatal mice were divided into five groups according to the developing stages. The mouse teeth were examined at the onset of root development by light and transmission electron microscopy. PV two-step immunohistochemical method was used to detect the expression of proliferating cell nuclear antigen(PCNA), OPN and BSP during the root formation. RESULTS: Hertwig's epithelial root sheath, which derived from the apical extensions of inner and outer enamel epithelium, was formed at 5-day mouse teeth and expressed PCNA positively. During the fuse of inner and outer enamel epithelium, some cells, which displayed the cytologic features of protein synthesis and secretion, could be found between the two epithelium cells. Desmosomal cell junctions were observed. The positive expressions of OPN were observed at the beginning of HERS. An accumulation of OPN could also be observed at the dentin-cementum junction during cementogenesis, but no positive BSP signals were seen at the onset of HERS. CONCLUSION: At onset of HERS, the inner enamel epithelium, outer enamel epithelium embrace several cells with developed cytoplasmic organelles, which may derive from stratum intermedium or stellate reticulum, and form a structure like enamel organ, which may be associated with initial cementogenesis. OPN, the non collagenous matrix proteins of cementum, may also take part in the formation of the dentin-cementum junction.

[Reaction of epithelial cell rests of malassez to tooth emergence and occlusal function reaction of epithelial cell rests of Malassez to tooth emergence and occlusal function].

UNLABELLED: OBJECTIVE To observe the morphology and proliferation of epithelial cell rests of Malassez (ECRM) during tooth emergence and occlusal function, and to evaluate its roles. METHODS: Cytokeratin 14 (CK14) was applied as special marker of ECRM cells. The morphology and distribution of ECRM were examined by light and transmission electron microscopy. PV two-step immunohistochemical method was used to detect the expression of CK14 and proliferating cell nuclear antigen (PCNA) in ECRM. RESULTS: ECRM experienced instinct morphological changes during tooth emergence and occlusal function. They were observed as network of epithelial cells labeled by CK14, especially in furcation level regions of mouse molars and active cell proliferation during occlusion found period. Cell apoptosis was observed in many ECRM by transmission electron microscopy during late stage of the progess. CONCLUSION: ECRM may not only an accidental left-over of early embryonic development but rather play significant roles in occlusion found period.