Proteomics Analysis of Human Dentin Reveals Distinct Protein Expression Profiles

Dental follicle cells and treated dentin matrix scaffold for tissue engineering the tooth root

Tissue engineering strategies to reconstruct tooth roots are an effective therapy for the treatment of tooth loss. However, strategies to successfully regenerate tooth roots have not been developed and optimized. In the present study, rat dental follicle stem cells (DFCs) were characterized, followed by a thorough investigation of tooth roots regeneration for a combination of DFCs seeding cells, treated dentin matrix (TDM) scaffolds, and an inductive alveolar fossa microenvironment. Eighteen clones derived from single DFCs were harvested; however, only three clones were amplified successfully more than five passages and 90-95 days in culture. Following 270 days or 30 passages, the heterogeneous DFCs showed suitable characteristics for seeding cells to regenerate tooth roots. However, various features, such as variable proliferation rates, differentiation characteristics, apoptosis rates, and total lifespan were observed in DFCs and the three clones. Importantly, upon transplantation of DFCs combined with TDM for four weeks, root-like tissues stained positive for markers of dental pulp and periodontal tissues were regenerated in the alveolar fossa, but not in the skull and omental pockets. These results indicate that tooth roots were successfully regenerated and suggest that the combination of DFCs with TDM in the alveolar fossa is a feasible strategy for tooth roots regeneration. This strategy could be a promising approach for the treatment of clinical tooth loss and provides a perspective with potential applications to regeneration of other tissues and organs.

Inflammatory mediators in fluid extracted from the coronal occlusal dentine of trimmed teeth

BACKGROUND

Chemokines and cytokines may occur in dentinal fluids in response to local infection and inflammation. To test this hypothesis, we assessed the presence and concentration of inflammatory mediators in fluid extracted from the coronal occlusal dentine of trimmed teeth.

DESIGN

Freshly extracted sound, carious, and restored molars were trimmed through the enamel to expose the underlying dentine, etched with 35% phosphoric acid, and rinsed. Fluid was extracted from the coronal occlusal dentine of these trimmed teeth by centrifugation at 2750 × g for 30 min.

RESULTS

When assessed by MALDI-TOF, fluid extracted from the coronal occlusal dentine from 16 molars contained at least 117 peaks with different masses suggesting that this fluid was rich with molecules within the appropriate mass range of potential mediators. Indeed, when assessed for chemokines and cytokines, fluid extracted from the coronal occlusal dentine from 25 extracted molars with caries lesions, 10 extracted restored molars with occlusal amalgam, and 77 extracted sound molars contained IL-1β, TNF-α, IL-6, IL-8, IL-12(p70), and IL-10. A significant elevation was found for TNF-α (p=0.041) in extracted fluid from teeth restored with amalgam fillings.

CONCLUSIONS

Overall, fluid extracted from the coronal occlusal dentine of trimmed teeth may be useful in identifying proteins and other molecules in dentine and pulpal fluids and determining their role as mediators in the pathogenesis of oral infection and inflammation.

Odontogenic differentiation of human dental pulp stem cells induced by preameloblast-derived factors

The differentiation of odontoblasts is initiated by the organization of differentiating ameloblasts during tooth formation. However, the exact roles of ameloblast-derived factors in odontoblast differentiation have not yet been characterized. We investigated the effects of preameloblast-conditioned medium (PA-CM) on the odontogenic differentiation of human dental pulp stem cells (hDPSCs) in vitro and in vivo. Furthermore, we analyzed the PA-CM by liquid chromatography-mass spectrometry to identify novel factors that facilitate odontoblast differentiation. In the co-culture of MDPC-23 cells or hDPSCs with mouse apical bud cells (ABCs), ABCs promoted differentiation of odontoblastic MDPC-23 cells and facilitated odontoblast differentiation of hDPSCs. PA-CM, CM from ABCs after 3 days culture, was most effective in increasing the dentin sialophosphoprotein promoter activity of odontoblastic MDPC-23 cells. When PA-CM-treated hDPSCs were transplanted into immunocompromised mice, they generated pulp-like structures lined with human odontoblast-like cells showing typical odontoblast processes. However, during recombinant human bone morphogenenetic protein 2-treated hDPSCs transplantation, some of the cells were entrapped in mineralized matrix possessing osteocyte characteristics. After proteomic analyses, we identified 113 types of proteins in PA-CM, of which we characterized 23. The results show that preameloblast-derived factors induce the odontogenic differentiation of hDPSCs and promote dentin formation.

Identification of novel accessible proteins bearing diagnostic and therapeutic potential in human pancreatic ductal adenocarcinoma

Pancreas ductal adenocarcinoma (PDAC) remains a deadly malignancy with poor early diagnostic and no effective therapy. Although several proteomic studies have performed comparative analysis between normal and malignant tissues, there is a lack of clear characterization of proteins that could be of clinical value. Systemically reachable ("potentially accessible") proteins, suitable for imaging technologies and targeted therapies represent a major group of interest. The current study explores potentially accessible proteins overexpressed in PDAC, employing innovative proteomics technologies. In the discovery phase, potentially accessible proteins from fresh human normal and PDAC tissues were ex vivo biotinylated, isolated and identified using 2D-nano-HPLC-MS/MS method. The analysis revealed 422 up-regulated proteins in the tumor, of which 83 (including protein isoforms) were evaluated as potentially accessible. Eleven selected candidates were further confirmed as up-regulated using Western blot and multiple reaction monitoring protein quantification. Of these, transforming growth factor beta-induced (TGFBI), latent transforming growth factor beta binding 2 (LTBP2), and asporin (ASPN) were further investigated by employing large scale immunohistochemistry-based validations. They were found to be significantly expressed in a large group of clinical PDAC samples compared to corresponding normal and inflammatory tissues. In conclusion, TGFBI, LTBP2, and ASPN are novel, overexpressed, and potentially accessible proteins in human PDAC. They bear the potential to be of clinical value for diagnostic and therapeutic applications and merit further studies using in vivo models.

Identification of azurocidin as a potential periodontitis biomarker by a proteomic analysis of gingival crevicular fluid

Background

The inflammatory disease periodontitis results in tooth loss and can even lead to diseases of the whole body if not treated. Gingival crevicular fluid (GCF) reflects the condition of the gingiva and contains proteins transuded from serum or cells at inflamed sites. In this study, we aimed to discover potential protein biomarkers for periodontitis in GCF proteome using LC-MS/MS.

Results

We identified 305 proteins from GCF of healthy individuals and periodontitis patients collected using a sterile gel loading tip by ESI-MS/MS coupled to nano-LC. Among these proteins, about 45 proteins were differentially expressed in the GCF proteome of moderate periodontitis patients when compared to the healthy individuals. We first identified azurocidin in the GCF, but not the saliva, as an upregulated protein in the periodontitis patients and verified its increased expression during periodontitis by ELISA using the GCF of the classified periodontitis patients compared to the healthy individuals. In addition, we found that azurocidin inhibited the differentiation of bone marrow-derived macrophages to osteoclasts.

Conclusions

Our results show that GCF collection using a gel loading tip and subsequent LC-MS/MS analysis following 1D-PAGE proteomic separation are effective for the analysis of the GCF proteome. Our current results also suggest that azurocidin could be a potential biomarker candidate for the early detection of inflammatory periodontal destruction by gingivitis and some chronic periodontitis. Our data also suggest that azurocidin may have an inhibitory role in osteoclast differentiation and, thus, a protective role in alveolar bone loss during the early stages of periodontitis.

The role of asporin in mineralization of human dental pulp stem cells

Human adult dental pulp stem cells (hDPSCs) are a unique precursor population isolated from postnatal dental pulp and have the ability to regenerate a reparative dentin-like complex. In this study, we investigated the role of Asporin in hDPSCs, which was identified as a matrix protein in our previous dentin proteomic analysis. We isolated a clonogenic, highly proliferative population of cells from adult human dental pulp. These isolated hDPSCs were confirmed by fluorescence activated cell sorting (FACS) using stem cell-specific markers and have shown multilineage differentiation potential. The localization of Asporin was identified by immunohistochemistry in the globular calcification region in the junction of predentin and dentin. The gene and protein expression levels of Asporin were enhanced at the early stage of and then reduced during the late stage of differentiation of hDPSCs in mineralization media. ASPN knock-down using a lentiviral system suppressed the mineralization of hDPSCs. These results suggest that ASPN plays positive roles in the mineralization of hDPSCs and predentin to dentin.

Protein content of molar-incisor hypomineralisation enamel

OBJECTIVES

The aim of the study was to compare the relative amounts and nature of the proteinous content of sound and molar-incisor hypomineralisation (MIH) enamel.

METHODS

TCA (20%) was used to dissolve the mineral phase and precipitate the proteins from enamel pieces sectioned from sound and MIH enamel. The protein content was estimated using a miniaturized version of the method of Lowry et al. Samples of the solubilised protein were separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), stained with Coomassie Blue R250 and tryptic fingerprint/mass spectrometry (MS/MS) of bands in excised gel pieces used for protein identification.

RESULTS

Compared to sound enamel, brown enamel showed a 15-21-fold higher protein content, and yellow and chalky enamel showed about 8-fold higher protein content. Tryptic fingerprint/MS performed on excised 50-70kDa areas demonstrated serum albumin, type I collagen and antitrypsin to be common to all types of enamel. Yellow and brown enamel showed more abundant serum albumin and antitrypsin, and the presence of serum antithrombin. Albumin is reported to be an inhibitor of crystal growth, and antitrypsin and antithrombin inhibit kallikrein 4 proteolytic activity.

CONCLUSIONS

The combination of the effects of serum proteins on developing enamel may result in elevated proteinous content and reduced mineral content as seen in MIH enamel.

Transcriptomes and Proteomes of Dental Follicle Cells

Ectomesenchymal dental stem cells could be feasible tools for dental tissue engineering. Dental follicle cells are a promising example, since they are capable of differentiation into various dental tissue cells, such as osteoblasts or cementoblasts. However, cellular mechanisms of cell proliferation and differentiation are not understood in detail. Basic knowledge of these molecular processes may shorten the time before ectomesenchymal dental stem cells can be exploited for bone augmentation in regenerative medicine. Recent developments in proteomics and transcriptomics have made information about genome-wide expression profiles accessible, which can aid in clarifying molecular mechanisms of cells. This review describes the transcriptomes and proteomes of dental follicle cells before and after differentiation, and compares them with differentially expressed populations from dental tissue or bone marrow.