Odontogenic potential of mesenchymal cells from hair follicle dermal papilla.

Dental pulp stem cells from teeth can be used for tooth regeneration. Although nondental stem cells derived from bone marrow can differentiate into odontoblast-like cells when recombined with embryonic oral epithelium, these cells can lose their ability to differentiate after an extended number of cell culture passages. There has been limited research to identify stem cells from other tissue sources to regenerate teeth. As another candidate source for mesenchymal stem cells, hair follicle has obtained much more attention recently because of its easy accessibility. In this study, cultured vibrissae follicle dermal papilla mesenchymal cells (FDPMCs) from adult C57BL/6 GFP mice can differentiate into adipocytes and osteoblasts in vitro. Moreover, in the inductive microenvironment generated by apical bud and dental mesenchyme from 7-day-old C57 mice, FDPMCs in vitro demonstrated odontogenic potential, as indicated by the morphological transformation, cell-cycle change and expression of tooth-specific markers. Under the same microenvironment, FDPMCs were incubated in vivo for 3 weeks. Coexpression of GFP and DSP proteins in the odontoblast layer was detected in the recovered implants, suggesting that GFP(+) FDPMCs can function as odontoblasts in vivo. Together, our data indicate for the first time that whisker FDPMCs from adult mice can differentiate to odontoblast-like cells.

[Experiment on inducing human dental pulp stem cells into neural-like cells].

OBJECTIVE: To explore the multi-differentiated capability of human dental pulp stem cells (hDPSCs) obtained by cell-clone culture approach and to determine the appropriate induced medium. METHODS: The cloned isolation and expansion of hDPSCs were preinduced for 24 h, and were subsequently replaced with neural-inductive medium containing certain concentration of dimethylsulfoxide (DMSO), butylated hydroxyanisode (BHA), forskolin, P-mercaptoethanol (p-ME) and hydrocortisone for 4 days. Then induced cells were analyzed by morphological observation, immnocytochemical staining for non-specific esterase (NSE) and glial fibrillary acidic protein (GFAP) expression, RT-PCR for GFAP mRNA. Meanwhile, the uninduced hDPSCs were used as negative control. RESULTS: The morphology of induced cells changed at the initial 12 h, and displayed a typical neuron-like cells at 24 h. There was a gradual increase in the number of these neuronal differentiated cells with continuous induction. Furthermore, immnocytochemical staining showed that the induced cell expressed NSE and GFAP, two marked enzymes of neuron cell. The GFAP mRNA was also detected in induced cells by RT-PCR assay. In contrast, the uninduced cells maintained its original appearance and had no expression on them. CONCLUSION: hDPSCs may possess potential of multiple-differentiation and may differentiate into neuron-like cells on certain inductive condition.

[Sequencing and bioinformatical analysis of virulent strain-specific DNA fragments from Streptococcus mutans].

OBJECTIVE: To search the DNA sequences specific to virulent strain of Streptococcus mutans in the public database and explore new genes or new functions of already known genes from Streptococcus mutans of serotype c and suppose their functions. METHODS: Thirty-one DNA fragments unique to virulent strain of Streptococcus mutans were sequenced. The sequences of these presumptive virulence DNA fragments were subjected to search through software BLASTn and BLASTx in public database, and their putative biological functions were analyzed. RESULTS Two clones were picked repeatedly. The size of the remaining DNA fragments ranged from 113 bp to 776 bp. The average G+C content was 38.59%, similar to that of the gene-coding sequences in Streptococcus mutans strain UA159 whose genome sequences were just complete. Of the twenty-nine DNA fragments, five potentially represented new DNA fragments in Streptococcus mutans, thus registered and obtained their gene's accession number in GenBank. The remaining DNA fragments showed high homology to known genes of Streptococcus mutans strain UA159. Their predicted functions of these fragments were associated to bacterial signal transduction, transcriptional regulation, stress-damage repair, biochemical metabolism, outer membrane protein synthesis, adhesion on tooth surface and hypothetical proteins. CONCLUSION: The gene analysis, identification and functional forecasting were carried out through bioinformatics associated software and database to find out new genes and new functions of known genes, and to supply the groundwork for researches in gene functions.

Cell pellets from dental papillae can reexhibit dental morphogenesis and dentinogenesis.

We isolated dental papilla mesenchymal cells (DPMCs) from different rat incisor germs at the late bell stage and incubated them as cell pellets in polypropylene tubes. In vitro pellet culture of DPMCs presented several crucial characteristics of odontoblasts, as indicated by accelerated mineralization, positive immunostaining for dentin sialophosphoprotein and dentin matrix protein 1, and expression of dentin sialophosphoprotein mRNA. The allotransplantation of these pellets into renal capsules was also performed. Despite the absence of dental epithelial components, dissociated DPMCs with a complete loss of positional information rapidly underwent dentinogenesis and morphogenesis, and formed a cusp-like dentin-pulp complex containing distinctive odontoblasts, predentin, dentin, and dentinal tubules. These results imply that DPMCs at the late bell stage can reexhibit the dental morphogenesis and dentinogenesis by themselves, and epithelial-mesenchymal interactions at this stage may not be indispensable. Furthermore, different DPMC populations from the similar stage may keep the same developmental pattern.

[IRF6 gene mutation analysis in a van Der Woude syndrome family in Henan province].

PURPOSE: To investigate IRF6 gene mutation in a van Der Woude syndrome (VWS) family in Henan province. METHODS: PCR and DNA sequencing was employed to detect the mutation of IRF6.Secondary construction transformation analysis was performed using PIX-Protein Identification software. RESULTS: A CGC>TGC(r.279c-->t) transversion of IRF6 was identified in condon 6, showing complete segregation with the disease phenotypes and was resulting in changes of the secondary constructure of IRF6. CONCLUSION: VWS is caused by mutations in IRF6 gene, and IRF6 is closely related to the development of lip, palate and tooth.

[Tissue engineering of dentin-pulp complex-like structures by human dental mesenchymal cells].

OBJECTIVE: To establish three-dimensional culture model of human dental mesenchymal cells and bioengineer in vivo with ceramic bovine bone (CBB) and Collagraft as scaffolds. METHODS: Human dental mesenchymal cells induced upon stimulation of bFGF and IGF-1 or TGF-beta(1) were implanted onto CBB and Collagraft containing the same kinds of growth factors respectively. Then cell/scaffold constructs were transplanted into nude mice to establish in vivo culture model of dental mesenchymal cells. Control groups were set up at the same time. After 4 weeks or 10 weeks, the implants were taken out for histological and immunohistochemical analysis. RESULTS: Within 10-week implant tissues, typical dentin-pulp complex-like structures were generated in scaffolds containing growth factors. Human dentin sialoprotein (DSP) was expressed in the newly formed dentin. This phenomenon wasn't observed in control groups and 4-week implants. CONCLUSIONS: Dentin-pulp complex-like structures could be bioengineered successfully with human dental mesenchymal cells and CBB or Collagrafts containing growth factors in nude mice.