Genome-wide gene expression profiles of dental follicle stem cells

Osteogenic differentiation potential and quantification of fresh and cryopreserved dental follicular stem cells-an in vitro analysis

Purpose: To isolate and characterize mesenchymal stem cells of dental follicle from fresh and cryopreserved samples and to test any significant difference in their osteogenic differentiation potential by using digital imaging software. We also investigated whether the cryoprotectant used and its concentration is able to maintain cell count and viability. Methods: Mesenchymal stem cells (MSCs) were isolated from dental follicle of impacted third molars. The osteogenic differentiation potential of dental follicle stem cells was assessed using alizarin red and alkaline phosphatase staining followed by digital imaging quantification of the stains. Results: Dental follicle cells have shown typical characterisation by exhibiting the stem cell stromal markers and hematopoietic markers, but there was variance in the percentage of expression in fresh and cryopreserved samples. There was considerable osteogenic differentiation potential in the fresh sample compared to cryopreserved sample. The cell count and viability were preserved in both samples. Conclusions: The results in the study have shown wide variation of osteogenic differentiation potential in fresh and cryopreserved samples. Also, the cryoprotectant was found to be effective in its purpose at the specified concentration.

STRO-1 positive cell expansion during osteogenic differentiation: A comparative study of three mesenchymal stem cell types of dental origin

OBJECTIVE

Although the osteogenic differentiation potential of mesenchymal stem cells of dental origin is well established, the roles of different marker proteins in this process remain to be clarified. Our aim was to compare the cellular and molecular changes, focusing in particular on mesenchymal stem cell markers, during in vitro osteogenesis in three dental stem cell types: dental follicle stem cells (DFSCs), periodontal ligament stem cells (PDLSCs) and dental pulp stem cells (DPSCs).

DESIGN

Human DFSCs, PDLSCs and DPSCs were isolated, cultured and their osteogenic differentiation was induced for 3 weeks. Mineralization was assessed by von Kossa staining and calcium concentration measurements. The expression of mesenchymal and osteogenic markers was studied by immunocytochemistry and qPCR techniques. Alkaline phosphatase (ALP) activity and the frequency of STRO-1 positive cells were also quantified.

RESULTS

The three cultures all showed abundant mineralization, with high calcium content by day 21. The expression of vimentin and nestin was sustained after osteogenic induction. The osteogenic medium induced a considerable elevation of STRO-1 positive cells. By day 7, the ALP mRNA level had increased more than 100-fold in DFSCs, PDLSCs, and DPSCs. Quantitative PCR results indicated dissimilarities of osteoblastic marker levels in the three dental stem cell cultures.

CONCLUSIONS

DFSCs, PDLSCs and DPSCs have similar functional osteogenic differentiation capacities although their expressional profiles of key osteogenic markers show considerable variations. The STRO-1 positive cell fraction expands during osteogenic differentiation while vimentin and nestin expression remain high. For identification of stemness, functional studies rather than marker expressions are needed.

Soluble silica stimulates osteogenic differentiation and gap junction communication in human dental follicle cells

Several studies have indicated that dietary silicon (Si) is beneficial for bone homeostasis and skeletal health. Furthermore, Si-containing bioactive glass biomaterials have positive effects on bone regeneration when used for repair of bone defects. Si has been demonstrated to stimulate osteoblast differentiation and bone mineralisation in vitro. However, the mechanisms underlying these effects of Si are not well understood. The aim of the present study was to investigate the effects of soluble Si on osteogenic differentiation and connexin 43 (CX43) gap junction communication in cultured pluripotent cells from human dental follicles (hDFC). Neutral Red uptake assay demonstrated that 25 μg/ml of Si significantly stimulated hDFC cell proliferation. Dosages of Si above 100 μg/ml decreased cell proliferation. Alizarin Red staining showed that osteogenic induction medium (OIM) by itself and in combination with Si (25 μg/ml) significantly increased mineralisation in hDFC cultures, although Si alone had no such effect. The expression of osteoblast-related markers in hDFC was analysed with RT-qPCR. OSX, RUNX2, BMP2, ALP, OCN, BSP and CX43 genes were expressed in hDFC cultured for 1, 7, 14 and 21 days. Expression levels of BMP-2 and BSP were significantly upregulated by OIM and Si (25 μg/ml) and were also induced by Si alone. Notably, the expression levels of OCN and CX43 on Day 21 were significantly increased only in the Si group. Flow cytometric measurements revealed that Si (50 μg/ml) significantly increased CX43 protein expression and gap junction communication in hDFC. Next-generation sequencing (NGS) and bioinformatics processing were used for the identification of differentially regulated genes and pathways. The influence of OIM over the cell differentiation profile was more prominent than the influence of Si alone. However, Si in combination with OIM increased the magnitude of expression (up or down) of the differentially regulated genes. The gene for cartilage oligomeric matrix protein (COMP) was the most significantly upregulated. Genes for the regulator of G protein signalling 4 (RGS4), regulator of G protein signalling 2 (RGS2), and matrix metalloproteinases (MMPs) 1, 8, and 10 were also strongly upregulated. Our findings reveal that soluble Si stimulates Cx43 gap junction communication in hDFC and induces gene expression patterns associated with osteogenic differentiation. Taken together, the results support the conclusion that Si is beneficial for bone health.

Foxc2 and BMP2 Induce Osteogenic/Odontogenic Differentiation and Mineralization of Human Stem Cells from Apical Papilla

As a transcription factor regulated by bone morphogenetic protein 2 (BMP2), Forkhead c2 (Foxc2) plays a pivot role in osteogenesis/odontogenesis. However, the role of Foxc2 and BMP2 in regulating osteo-/odontogenic differentiation and mineralization of stem cells from apical papilla (SCAP) is still uncertain. In this research, overexpression of Foxc2 gene significantly improved the proliferation of SCAP four days and eight days after transfection, but overexpression of both Foxc2 and BMP2 genes significantly inhibited the proliferation of SCAP eight days after transfection. RT-qPCR and western blot results indicated that SCAP-Foxc2-BMP2 significantly upregulated osteo-/odontogenic genes and proteins at most of the time points in SCAP after transfection. Moreover, SCAP-Foxc2-BMP2 formed notably more alkaline phosphatase-positive and alizarin red-positive mineralized nodules than other three group cells sixteen days after transfection. In conclusion, our findings revealed that Foxc2 and BMP2 synergistically promoted osteo-/odontogenic differentiation and mineralization of SCAP in vitro.

Proteomic analysis of the effects of CSF-1 and IL-1α on dental follicle cells

Tooth eruption is a complex physiological process involving both osteogenesis and bone resorption. Signals from the dental follicle (DF) regulate bone remodeling during tooth eruption. Interleukin-1α (IL-1α) may be the initial promoter of tooth eruption, whereas colony‑stimulating factor‑1 (CSF‑1) may attract monocytes into the DF and stimulate osteoclast differentiation. In the present study, differential proteomics was employed to explore protein changes in rat DF cells (DFCs) under the effects of CSF‑1 and IL‑1α. A total of 47 protein spots were differentially expressed in rat DFCs, and 40 protein spots were identified by MALDI‑TOF‑MS. The identified proteins were grouped into functional categories including cytoskeletal proteins, metal‑binding proteins, proteins involved in secretion and degradation, cell cycle proteins and stress proteins. In IL‑1α‑induced rat DFCs, 31 proteins were upregulated compared with the control and included heat shock protein β‑1 (HSP25, also known as HSP27/HSPβ1), vimentin, TMEM43, the GTP‑binding protein Rab‑3D, 6‑pyruvoyl tetrahydrobiopterin synthase and actin. In total, 7 proteins were downregulated, including serum albumin, GIPC1, DNA primase large subunit, cullin‑5 and cyclin‑G1. In CSF‑1‑induced rat DFCs, 3 proteins were upregulated and 7 proteins were downregulated when compared with the controls. The upregulated proteins included the GTP‑binding protein Rab‑3D and α‑actin. The downregulated proteins included cullin‑5, serum albumin, PDZ domain‑containing protein and cyclin‑G1. The differential expression of vimentin, actin, HSP25 and Rab‑3D was verified by western blotting and reverse transcription‑quantitative polymerase chain reaction analyses. The present findings provide an insight into the mechanisms involved in tooth eruption.

Immunomodulatory properties and in vivo osteogenesis of human dental stem cells from fresh and cryopreserved dental follicles

In our previous study, dental follicle tissues from extracted wisdom teeth were successfully cryopreserved for use as a source of stem cells. The goals of the present study were to investigate the immunomodulatory properties of stem cells from fresh and cryopreserved dental follicles (fDFCs and cDFCs, respectively) and to analyze in vivo osteogenesis after transplantation of these DFCs into experimental animals. Third passage fDFCs and cDFCs showed similar expression levels of interferon-γ receptor (CD119) and major histocompatibility complex class I and II (MHC I and MHC II, respectively), with high levels of CD119 and MHC I and nearly no expression of MHC II. Both fresh and cryopreserved human DFCs (hDFCs) were in vivo transplanted along with a demineralized bone matrix scaffold into mandibular defects in miniature pigs and subcutaneous tissues of mice. Radiological and histological evaluations of in vivo osteogenesis in hDFC-transplanted sites revealed significantly enhanced new bone formation activities compared with those in scaffold-only implanted control sites. Interestingly, at 8 weeks post-hDFC transplantation, the newly generated bones were overgrown compared to the original size of the mandibular defects, and strong expression of osteocalcin and vascular endothelial growth factor were detected in the hDFCs-transplanted tissues of both animals. Immunohistochemical analysis of CD3, CD4, and CD8 in the ectopic bone formation sites of mice showed significantly decreased CD4 expression in DFCs-implanted tissues compared with those in control sites. These findings indicate that hDFCs possess immunomodulatory properties that involved inhibition of the adaptive immune response mediated by CD4 and MHC II, which highlights the usefulness of hDFCs in tissue engineering. In particular, long-term preserved dental follicles could serve as an excellent autologous or allogenic stem cell source for bone tissue regeneration as well as a valuable therapeutic agent for immune diseases.

Stem Cells in Teeth and Craniofacial Bones

Stem cells are remarkable, and stem cell-based tissue engineering is an emerging field of biomedical science aiming to restore damaged tissue or organs. In dentistry and reconstructive facial surgery, it is of great interest to restore lost teeth or craniofacial bone defects using stem cell-mediated therapy. In the craniofacial region, various stem cell populations have been identified with regeneration potential. In this review, we provide an overview of the current knowledge concerning the various types of tooth- and craniofacial bone-related stem cells and discuss their in vivo identities and regulating mechanisms.