Periodontal tissue engineering with stem cells from the periodontal ligament of human retained deciduous teeth

The osteogenic effects of sappanchalcone in vitro and in vivo

BACKGROUND AND OBJECTIVES

The utilization of natural products to enhance the function of periodontal ligament cells (PDLCs) has emerged as a popular area of research. Recent investigations have demonstrated that sappanchalcone (SC) possesses pharmacological properties such as anti-inflammatory and osteoprotective effects. This study aims to explore the impact of SC on the in vivo and in vitro osteogenic differentiation ability of PDLCs.

MATERIALS

Cell proliferation was quantified using the CCK-8 assay, while gene expression levels were assessed through qRT-PCR analysis. Osteoblast differentiation capacity was evaluated by employing Alizarin red staining (ARS), alkaline phosphatase (ALP) staining and western blot (WB) analysis. A rat model of periodontitis was established utilizing the tether-wire method. Micro-CT imaging and hematoxylin and eosin (HE) staining were employed to evaluate alveolar bone resorption. Masson's trichrome staining was utilized to observe fiber alignment, whereas immunohistochemistry (IHC) techniques were applied for detecting osteogenic and inflammatory factors.

RESULTS

The results from the CCK-8 assay indicate no observed cytotoxicity for concentrations of 1, 5, or 10 nM for SC treatment (p < .05), while qRT-PCR analysis demonstrates a significant decrease in inflammatory factors such as MMP-1 and IL-6 with treatment by SC (p < .05). Additionally, western blotting reveals an increase in protein expression levels of Runx2 and OPN within PDLCs treated with SC compared to control groups (p < .05), which is further supported by ARS and ALP staining indicating an increase in mineralized nodules formation along with elevated ALP content within these cells following treatment with this compound (p < .05). Finally, both HE staining as well as micro-CT imaging suggest potential benefits associated with using this compound including slowing alveolar bone resorption while simultaneously promoting junctional epithelium proliferation.

CONCLUSIONS

Our in vitro and in vivo findings suggest that SC can effectively enhance the inflammatory response of PDLCs and promote their osteogenic differentiation ability under inflammatory conditions, indicating its potential as a promising therapeutic agent for improving periodontal inflammation and bone formation.

Comparison of Periodontal Ligament Stem Cells with Mesenchymal Stem Cells from Other Sources: A Scoping Systematic Review of In vitro and In vivo Studies

OBJECTIVE

The application of stem cells in regenerative medicine depends on their biological properties. This scoping review aimed to compare the features of periodontal ligament stem cells (PDLSSCs) with stem cells derived from other sources.

DESIGN

An electronic search in PubMed/Medline, Embase, Scopus, Google Scholar and Science Direct was conducted to identify in vitro and in vivo studies limited to English language.

RESULTS

Overall, 65 articles were included. Most comparisons were made between bone marrow stem cells (BMSCs) and PDLSCs. BMSCs were found to have lower proliferation and higher osteogenesis potential in vitro and in vivo than PDLSCs; on the contrary, dental follicle stem cells and umbilical cord mesenchymal stem cells (UCMSCs) had a higher proliferative ability and lower osteogenesis than PDLSCs. Moreover, UCMSCs exhibited a higher apoptotic rate, hTERT expression, and relative telomerase length. The immunomodulatory function of adipose-derived stem cells and BMSCs was comparable to PDLSCs. Gingival mesenchymal stem cells showed less sensitivity to long-term culture. Both pure and mixed gingival cells had lower osteogenic ability compared to PDLSCs. Comparison of dental pulp stem cells (DPSCs) with PDLSCs regarding proliferation rate, osteo/adipogenesis, and immunomodulatory properties was contradictory; however, in vivo bone formation of DPSCs seemed to be lower than PDLSCs.

CONCLUSION

In light of the performed comparative studies, PDLSCs showed comparable results to stem cells derived from other sources; however, further in vivo studies are needed to determine the actual pros and cons of stem cells in comparison to each other.

Photobiomodulation Effects on Periodontal Ligament Stem Cells: A Systematic Review of In Vitro Studies

BACKGROUND

Stem cell therapy has been considered to play a paramount role in the treatment modalities available for regenerative dentistry. The established beneficial effects of photobiomodulation (PBM) at the cellular level have led to the combined use of these two factors (PBM and stem cells). The main goal of this study was firstly to critically appraise the effects of PBM on periodontal ligament stem cells (PDLSCs), and secondly to explore the most effective PBM protocols applied.

METHODS

Pubmed, Cochrane, Scopus, Science Direct, and Google Scholar search engines were used to identify experimental in vitro studies in which PBM was applied to cultured PDLSCs. After applying specific keywords, additional filters, and inclusion/exclusion criteria, a preliminary number of 245 articles were narrowed down to 11 in which lasers and LEDs were used within the 630 - 1064 nm wavelength range. Selected articles were further assessed by three independent reviewers for strict compliance with PRISMA guidelines, and a modified Cochrane risk of bias to determine eligibility.

STATISTICAL ANALYSIS

The dataset analysed was extracted from the studies with sufficient and clearly presented PBM protocols. Simple univariate regression analysis was performed to explore the significance of contributions of potential quantitative predictor variables toward study outcomes, and a one-way ANOVA model was employed for testing differences between the laser or LED sources of the treatments. The significance level for testing was set at α = 0.05.

RESULTS

The proliferation rate, osteogenic differentiation, and expression of different indicative genes for osteogenesis and inflammation suppression were found to be positively affected by the application of various types of lasers and LEDs. With regard to the PBM protocol, only the wavelength variable appeared to affect the treatment outcome; indeed, the 940 nm wavelength parameter was found not to exert a favourable effect.

CONCLUSIONS

Photobiomodulation can enhance the stemness and differentiation capacities of periodontal ligament stem cells. Therefore, for PBM protocols, there remains no consensus amongst the scientific community. Statistical analyses performed here indicated that the employment of a near-infrared (NIR) wavelength of 940 nm may not yield a significant favourable outcome, although those within the 630 - 830 nm range did so. Concerning the fluence, it should not exceed 8 J/cm2 when therapy is applied by LED devices, and 4 J/cm2 when applied by lasers, respectively.

A Review of In Vivo and Clinical Studies Applying Scaffolds and Cell Sheet Technology for Periodontal Ligament Regeneration

Different approaches to develop engineered scaffolds for periodontal tissues regeneration have been proposed. In this review, innovations in stem cell technology and scaffolds engineering focused primarily on Periodontal Ligament (PDL) regeneration are discussed and analyzed based on results from pre-clinical in vivo studies and clinical trials. Most of those developments include the use of polymeric materials with different patterning and surface nanotopography and printing of complex and sophisticated multiphasic composite scaffolds with different compartments to accomodate for the different periodontal tissues' architecture. Despite the increased effort in producing these scaffolds and their undoubtable efficiency to guide and support tissue regeneration, appropriate source of cells is also needed to provide new tissue formation and various biological and mechanochemical cues from the Extraccellular Matrix (ECM) to provide biophysical stimuli for cell growth and differentiation. Cell sheet engineering is a novel promising technique that allows obtaining cells in a sheet format while preserving ECM components. The right combination of those factors has not been discovered yet and efforts are still needed to ameliorate regenerative outcomes towards the functional organisation of the developed tissues.

Periodontal ligament stem cell isolation protocol: A systematic review

Despite the plethora of literature regarding isolation and characterization of periodontal ligament stem cells (PDLSCs), due to the existence of controversies in the results, in this comprehensive review, we aimed to summarize and compare the effect of isolation methods on PDLSC properties, including clonogenicity, viability/proliferation, markers expression, cell morphology, differentiation, and regeneration. Moreover, the outcomes of included studies, considering various parameters such as teeth developmental stages, donor age, periodontal ligament health status, and part of the teeth root from which PDLSCs were derived, have been systematically discussed. It has been shown that from included studies PDLSCs can be isolated from teeth from any developmental stages, any health status condition, and any donor age. Also, a non-enzymatic digestion method, named as an explant or outgrowth technique, is a suitable protocol for of PDLSCs isolation.

Hypes and Hopes of Stem Cell Therapies in Dentistry: a Review

One of the most exciting advances in life science research is the development of 3D cell culture systems to obtain complex structures called organoids and spheroids. These 3D cultures closely mimic in vivo conditions, where cells can grow and interact with their surroundings. This allows us to better study the spatio-temporal dynamics of organogenesis and organ function. Furthermore, physiologically relevant organoids cultures can be used for basic research, medical research, and drug discovery. Although most of the research thus far focuses on the development of heart, liver, kidney, and brain organoids, to name a few, most recently, these structures were obtained using dental stem cells to study in vitro tooth regeneration. This review aims to present the most up-to-date research showing how dental stem cells can be grown on specific biomaterials to induce their differentiation in 3D. The possibility of combining engineering and biology principles to replicate and/or increase tissue function has been an emerging and exciting field in medicine. The use of this methodology in dentistry has already yielded many interesting results paving the way for the improvement of dental care and successful therapies.

Establishing a technique for isolation and characterization of human periodontal ligament derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are extensively used in tissue regenerative procedures. One source of MSCs is the periodontal ligament (PDL) of teeth. Isolation of MSCs from extracted teeth is reasonably simple, being less invasive and presenting fewer ethical concerns than does the harvesting of MSC’s from other sites. The objectives of this study were to isolate and characterize the PDL stem cells (PDLSC) from healthy adults’ extracted teeth and then to characterize them by comparing them with bone-marrow derived MSCs (BMMSC).

Methods

The PDL tissue was scraped from the roots of freshly extracted teeth to enzymatically digest using collagenase. The cells were sub-cultured. Flow-cytometric analysis for the MSC surface-markers CD105, CD73, CD166, CD90, CD34, CD45 and HLA-DR was performed. To confirm the phenotype, total RNA was extracted to synthesize cDNA and which was then subjected to RT-PCR. The gene-expression for Oct4A, Sox2, NANOG and GAPDH was determined by gel-electrophoresis. To assess their multilineage potential, cells were cultured with osteogenic, chondrogenic and adipogenic medium and then stained by Alizarin-red, Alcian-blue and Oil-Red-O respectively. MSCs from the bone-marrow were processed similarly to serve as controls.

Results

The cells isolated from extracted teeth expanded successfully. On flow-cytometric analysis, the cells were positive for CD73, CD90, CD105, CD166 and negative for CD34, CD45 and HLA-DR. The PDLSCs expressed Oct4A, Sox2, and NANOG mRNA with GAPDH expression. Cells cultured in the osteogenic, chondrogenic and adipogenic media stained positive for Alizarin-red, Alcian-blue and Oil- Red-O respectively. The surface marker expression and the trilineage differentiation characteristics were comparable to those of the BMMSCs.

Conclusions

The periodontal ligament tissue of extracted teeth is a potential source of therapeutically useful MSCs. Harvesting them is not invasive and are a promising source of MSC as the PDLSCs showed characteristics similar to those of the highly regarded MSC’s derived from bone-marrow.

Dental tissue-derived stem cell sheet biotechnology for periodontal tissue regeneration: A systematic review

OBJECTIVE

This study aimed to conduct a systematic review of the use of a cell sheet formed by mesenchymal stem cells derived from dental tissues (ddMSCs) for periodontal tissue regeneration in animal models in comparison with any other type of regenerative treatment.

DESIGN

PubMed and Scopus databases were searched for relevant studies up to December 2020. The review was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines.

RESULTS

Of the 1542 potentially relevant articles initially identified, 33 fulfilled the eligibility criteria and were considered for this review. Even with a wide variety of selected study methods, the periodontal tissue was always regenerated; this indicates the potential for the use of these cell sheets in the future of periodontics. However, this regeneration process is not always complete.

CONCLUSION

Despite the implantation, ddMSCs sheets have a great potential to be used in the regeneration of periodontal tissue. More in vivo studies should be conducted using standardized techniques for cell sheet implantation to obtain more robust evidence of the relevance of using this modality of cell therapy for periodontal tissue regeneration.

Multipotent stem cells from apical pulp of human deciduous teeth with immature apex

Isolation of high-quality human postnatal stem cells from accessible sources is an important goal for dental tissue engineering. Stem cells from developing organs are a better cell source but are hard to obtain. With extensive caries that are difficult to restore, the extracted deciduous tooth with an immature apex is a developing organ for investigation. In the present study, a cell population from the tip of apical pulp of human deciduous teeth with an immature apex was isolated and termed apical pulp-derived cells of deciduous teeth (De-APDCs). De-APDCs expressed STRO-1, CD44, CD90 and CD105 but not CD34 or CD45. Furthermore, De-APDCs demonstrated a significantly higher clonogenic and proliferative ability and osteo/dentinogenic differentiation capacity than dental pulp cells from exfoliated deciduous teeth (De-DPCs) (P < 0.05). Differentiation potential toward adipogenic, neurogenic and chondrogenic lineages was also observed in induced De-APDCs. In addition, after De-APDCs were seeded into hydroxyapatite/tricalcium phosphate (HA/TCP) scaffolds and transplanted into nude mice, they were able to regenerate dentin/pulp-like structures aligned with human odontoblast-like cells. In conclusion, De-APDCs, which are derived from a developing tissue, represent an accessible and prospective cell source for tooth regeneration.

Downregulation of miR-184 facilitates osseous differentiation in periodontal ligament stem cells by modulating nuclear factor I-C

Background/purpose

PDLSCs (periodontal ligament stem cells), derived from dental tissues, are candidate cells for regeneration of dental tissues. MiRNAs could regulate osteogenic differentiation and the transformation into osteoblasts. This study was conducted to figure out how miR-184 regulates osteoblastic differentiation in PDLSCs.

Materials and methods

PDLSCs were isolated from premolars, and the osteoblastic differentiation was validated via Alizarin red staining and determination of ALP (alkaline phosphatase) activity. Expression of osteogenic specific genes were evaluated by western blot, and the expression pattern of miR-184 was determined by qRT-PCR. Target gene of miR-184 was then verified by dual luciferase reporter assay.

Results

Osteogenic-induced PDLSCs were successfully established with increased mineral deposition, ALP activity and protein expression of RUNX2 (runt-related transcription factor 2), osterix and BSP (bone sialoprotein). MiR-184 was reduced during osteoblastic differentiation of PDLSCs, and over-expression of miR-184 suppressed osteoblastic differentiation, as evidenced by reduction in mineral deposition, ALP activity and protein expression of RUNX2, osterix and BSP. MiR-184 could target NFI-C (nuclear factor I-C), and inhibit NFI-C expression in PDLSCs. NFI-C was enhanced during osteoblastic differentiation of PDLSCs, suggesting negative correlation with miR-184. Forced NFI-C expression promoted osteoblastic differentiation, and counteracted with the suppressive effects of miR-184 on osteoblastic differentiation.

Conclusion

Downregulation of miR-184 facilitates osteoblastic differentiation in PDLSCs by modulating NFI-C, providing novel therapeutic strategy for regeneration of dental tissues.

Rutin promotes osteogenic differentiation of periodontal ligament stem cells through the GPR30-mediated PI3K/AKT/mTOR signaling pathway

Rutin is one of the flavonoids found in fruits and vegetables. Recent reports have revealed that rutin is a major player in proliferation and bone development. However, data on how rutin regulates the proliferation of periodontal ligament stem cells (PDLSCs), as well as the differentiation of osteogenic cells are scanty. Here, our findings showed that rutin enhanced PDLSCs proliferation, increased ALP activity, and matrix mineralization. Moreover, rutin significantly promoted the expression of osteogenic genes and elevated phosphorylated AKT and mTOR. Treatment with LY294002 reversed these effects by inhibiting PI3K. We also found that the expression levels of GPR30 were increased by rutin. Interestingly, this upregulation was not altered after the addition of LY294002. In addition, G15, a selective antagonist of GPR30, could reduce the beneficial effects induced by rutin and interfere with the modulation of PI3K/AKT/mTOR signal transduction. Collectively, our findings revealed that rutin increased proliferation and osteogenic differentiation of PDLSCs through GPR30-mediated PI3K/AKT/mTOR signal transduction. Therefore, it could be deduced that rutin as a certain flavonoid possesses therapeutic value for periodontal bone regeneration and tissue engineering.

Impact statement

In our study, the effects and mechanisms of rutin on the osteogenic differentiation and proliferation of PDLSCs were investigated. Our findings might provide basic knowledge and guidance to understand and use rutin in the bioengineering of the periodontal tissues and regeneration of bones. The following is a short description of the main findings: rutin promotes the osteogenic differentiation and proliferation of PDLSCs; PI3K/AKT/mTOR signal pathway mediates the effects of rutin on PDLSCs; rutin activates PI3K/AKT/mTOR signal pathway via GPR30.

Biomaterial-Based Approaches for Regeneration of Periodontal Ligament and Cementum Using 3D Platforms

Currently, various tissue engineering strategies have been developed for multiple tissue regeneration and integrative structure formations as well as single tissue formation in musculoskeletal complexes. In particular, the regeneration of periodontal tissues or tooth-supportive structures is still challenging to spatiotemporally compartmentalize PCL (poly-ε-caprolactone)-cementum constructs with micron-scaled interfaces, integrative tissue (or cementum) formations with optimal dimensions along the tooth-root surfaces, and specific orientations of engineered periodontal ligaments (PDLs). Here, we discuss current advanced approaches to spatiotemporally control PDL orientations with specific angulations and to regenerate cementum layers on the tooth-root surfaces with Sharpey's fiber anchorages for state-of-the-art periodontal tissue engineering.

Berberine improves advanced glycation end products‑induced osteogenic differentiation responses in human periodontal ligament stem cells through the canonical Wnt/β‑catenin pathway

The aim of the present study was to investigate the effects of advanced glycation end products (AGEs) and berberine hydrochloride (BBR) on the osteogenic differentiation ability of human periodontal ligament stem cells (hPDLSCs) in vitro, and their underlying mechanisms. hPDLSCs were subjected to osteogenic induction and were treated with AGEs or AGEs + BBR. Following varying numbers of days in culture, alkaline phosphatase (ALP) activity assays, ALP staining, alizarin red staining, ELISAs, and reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blot analyses were performed to determine the osteogenic differentiation ability of hPDLSCs; RT‑qPCR, western blot analysis, and immunofluorescence staining were conducted to investigate the underlying mechanisms. The canonical Wnt/β‑catenin pathway inhibitor XAV‑939 and agonist CHIR‑99021 were used to determine the contribution of the canonical Wnt/β‑catenin pathway to differentiation. Treatment with AGEs resulted in reduced ALP activity and Collagen I protein levels, decreased ALP staining, fewer mineralized nodules, and downregulated expression of osteogenic‑specific genes [Runt‑related transcription factor 2 (Runx2), Osterix, ALP, osteopontin (OPN), Collagen I and osteocalcin (OCN)] and proteins (Runx2, OPN, BSP and OCN); however, BBR partially rescued the AGE‑induced decrease in the osteogenic potential of hPDLSCs. Furthermore, AGEs activated the canonical Wnt/β‑catenin signaling pathway and promoted the nuclear translocation of β‑catenin; BBR partially attenuated this effect. In addition, XAV‑939 partially rescued the AGE‑induced reduction in the osteogenic potential of hPDLSCs, whereas CHIR‑99021 suppressed the BBR‑induced increase in the osteogenic potential of hPDLSCs. The present study indicated that AGEs attenuated the osteogenic differentiation ability of hPDLSCs, in part by activating the canonical Wnt/β‑catenin pathway; however, BBR attenuated these effects by inhibiting the canonical Wnt/β‑catenin pathway. These findings suggest a role for BBR in periodontal regeneration induced by hPDLSCs in patients with diabetes mellitus.

Strategic Tools in Regenerative and Translational Dentistry

Human oral-derived stem cells can be easily obtained from several oral tissues, such as dental pulp, periodontal ligament, from gingiva, or periapical cysts. Due to their differentiation potential, oral-derived mesenchymal stem cells are promising for tissue engineering and regenerative medicine. The regenerative ability showed by some oral tissues strongly depends on their sleeping adult stem cell populations that are able to repair small defects and to manage local inflammation. To date, researchers are working on effective and efficient methods to ensure safe and predictable protocols to translate stem cell research into human models. In the last decades, the challenge has been to finally use oral-derived stem cells together with biomaterials or scaffold-free techniques, to obtain strategic tools for regenerative and translational dentistry. This paper aims to give a clear point of view on state of the art developments, with some exciting insights into future strategies.

Bone Tissue Engineering Using Human Cells: A Comprehensive Review on Recent Trends, Current Prospects, and Recommendations

The use of proper cells for bone tissue engineering remains a major challenge worldwide. Cells play a pivotal role in the repair and regeneration of the bone tissue in vitro and in vivo. Currently, a large number of differentiated (somatic) and undifferentiated (stem) cells have been used for bone reconstruction alone or in combination with different biomaterials and constructs (e.g., scaffolds). Although the results of the cell transplantation without any supporting or adjuvant material have been very effective with regard to bone healing. Recent advances in bone scaffolding are now becoming new players affecting the osteogenic potential of cells. In the present study, we have critically reviewed all the currently used cell sources for bone reconstruction and discussed the new horizons that are opening up in the context of cell-based bone tissue engineering strategies.

Two Transcripts of FBXO5 Promote Migration and Osteogenic Differentiation of Human Periodontal Ligament Mesenchymal Stem Cells

OBJECTIVES

Enhanced migration and osteogenic differentiation of mesenchymal stem cells (MSCs) are beneficial for MSC-mediated periodontal tissue regeneration, a promising method for periodontitis treatment. FBXO5, a member of the F-box protein family, is involved in the osteogenic differentiation of MSCs. Here, we investigated the effect of FBXO5 on human periodontal ligament stem cells (hPDLSCs).

MATERIALS AND METHODS

hPDLSCs were isolated from periodontal ligament tissue. Lentivirus FBXO5 shRNA was used to silence FBXO5 expression. Two transcripts of FBXO5 were overexpressed and transduced into hPDLSCs via retroviral infection. Migration and osteogenic differentiation of hPDLSCs were evaluated using the scratch migration assay, alkaline phosphatase (ALP) activity, ALP staining, alizarin red staining, western blotting, and real-time polymerase chain reaction.

RESULTS

The expression of FBXO5 was upregulated after osteogenic induction in hPDLSCs. FBXO5 knockdown attenuated migration, inhibited ALP activity and mineralization, and decreased RUNX2, OSX, and OCN expression, while the overexpression of two transcript isoforms significantly accelerated migration, enhanced ALP activity and mineralization, and increased RUNX2, OSX, and OCN expression in hPDLSCs.

CONCLUSIONS

Both isoforms of FBXO5 promoted the migration and osteogenic differentiation potential of hPDLSCs, which identified a potential target for improving periodontal tissue regeneration.

The effect of strontium chloride on human periodontal ligament stem cells

The complete repair of periodontal structures remains an exciting challenge that prompts researchers to develop new treatments to restore the periodontium. Recent research has suggested strontium ion to be an attractive candidate to improve osteogenic activity. In this study, we have isolated a clonal finite cell line derived from human periodontal ligament (PDL) in order to assess whether and in which way different doses of SrCl₂ (from 0.5 to 500 μg/ml) can influence both the proliferation and the mineralization process, for future application in oral diseases. PDL cells were cloned by dilution plating technique and characterized by FACS. Cell proliferation analysis and mineralization were performed by [³H]-thymidine incorporation and spectrofluorometric assay. Results have evidenced that the higher SrCl₂ concentrations tested, from 25 to 500 μg/ml, have increased the proliferation activity after only 24 h of treatment. Interestingly, the same higher concentrations have decreased the mineralization, which was conversely increased by the lower ones, from 0.5 to 10 μg/ml. Our findings suggest the possible use of SrCl₂ in appropriate delivery systems that release, at different time points, the specific dose, depending on the biological response that we want to induce on periodontal ligament stem cells, providing a more efficient periodontal regeneration.

MicroRNA-214 Suppresses Osteogenic Differentiation of Human Periodontal Ligament Stem Cells by Targeting ATF4

Periodontitis is the main cause of adult tooth loss. Stem cell-based tissue engineering has become a promising therapy for periodontitis treatment. To date, human periodontal ligament stem cells (hPDLSCs) have been shown to be a favorable source for tissue engineering, but modulatory mechanisms of hPDLSCs remain unclear. Approximately 60% of mammalian genes are the targets of over 2000 miRNAs in multiple human cell types, and miRNAs are able to influence various biological processes in the human body, including bone formation. In this study, we found that after osteogenic induction, miR-214 was significantly decreased in hPDLSCs; therefore, we examined the effects of miR-214 on osteogenic differentiation. Computational miRNA target prediction analyses and luciferase reporter assays revealed that activating transcription factor 4 (ATF4) is a direct target of miR-214. We prepared cells overexpressing miR-214 and found that miR-214 negatively regulates osteogenic differentiation of hPDLSCs. For the target of miR-214, ATF4 protein expression level was decreased after induction. In conclusion, we found that miR-214-ATF4 axis is a novel pathway for regulating hPDLSC osteogenic differentiation.

Comparison of in vitro properties of periodontal ligament stem cells derived from permanent and deciduous teeth

Background. Stem cells have contributed to the development of tissue-engineered-based regenerative periodontal therapies. In order to find the best stem cell sources for such therapies, the biologic properties of stem cells isolated from periodontal ligaments (PDL) of deciduous (DePDLSC) and permanent (PePDLSC) teeth were comparatively evaluated. Methods. PDL stem cells were isolated from six sound fully erupted premolars and six deciduous canines of healthy subjects. In vitro biologic characteristics such as colony formation, viability, stem cell marker identification and osteogenic differentiation (using alkaline phosphatase analysis and Alizarin red staining) were comparatively assessed using one-way ANOVA and post hoc Tukey tests using SPSS 13.0. Results. Stem cell populations isolated from both groups were CD105+ and CD90+ and CD45‒. No statistically significant differences were found in stem cell markers, colony formation and viability. Both groups were capable of osteogenic differentiation. However, alkaline phosphatase activity test showed a statistically significant difference, with PePDLSC exhibiting higher alkaline phosphatase activity (P=0.000). No statistically significant difference was seen in quantitative alizarine red staining (P=0.559). Conclusion. Mesenchymal stem cells of PDL could successfully be isolated from permanent and deciduous teeth. A minor difference was observed in the osteogenic properties of the two cell types, which might affect their future clinical applications.

Comparative analysis of different feeder layers with 3T3 fibroblasts for culturing rabbits limbal stem cells

AIM

To explore the possibility of human umbilical cord mesenchymal stem cells (hUCMSCs), human umbilical vein endothelial cells (hUVECs), human dental pulp stem cells (hDPSCs) and human periodontal ligament stem cells (hPDLSCs) serving as feeder cells in co-culture systems for the cultivation of limbal stem cells.

METHODS

Different feeder layers were cultured in Dulbecco's modified Eagle's medium (DMEM)/F12 and were treated with mitomycin C. Rabbits limbal stem cells (LSCs) were co-cultured on hUCMSCs, hUVECs, hDPSCs, hPDLSCs and NIH-3T3, and then comparative analysis were made between each group to see their respective colony-forming efficiency (CFE) assay and immunofluorescence (IPO13,CK3/12).

RESULTS

The efficiency of the four type cells in supporting the LSCs morphology and its cellular differentiation was similar to that of NIH-3T3 fibroblasts as demonstrated by the immunostaining properties analysis, with each group exhibiting a similar strong expression pattern of IPO13, but lacking CK3 and CK12 expression in terms of immunostaining. But hUCMSCs, hDPSCs and hPDLSCs feeder layers were superior in promoting colony formation potential of cells when compared to hUVECs and feeder-cell-free culture.

CONCLUSION

hUCMSCs, hDPSCs and hPDLSCs can be a suitable alternative to conventional mouse NIH-3T3 feeder cells, so that risk of zoonotic infection can be diminished.

Comparative analysis of secretory factors from permanent- and deciduous-teeth periodontal ligament cells

OBJECTIVE

Studies of regenerative therapies have focused on the paracrine effects of mesenchymal stem cells, but little has been revealed about the humoral factors of periodontal ligament (PDL) stem cells. The aim of this study was to identify and compare the secretory factors of human permanent- and deciduous-teeth PDL cells (P-PDL and D-PDL cells, respectively) in order to understand the characteristics of these cells and their potential applications in regenerative therapies.

DESIGN

Conditioned media were collected from P-PDL and D-PDL cells (P-PDL-CM and D-PDL-CM, respectively). These media were analyzed with high-performance liquid-chromatography-coupled electrospray ionization tandem mass spectrometry and a cytokine membrane assay. In addition, Western blot analysis was performed to verify the differences between the two media.

RESULTS

Cytokines related to neurogenesis (NT-3 and NT-4) and angiogenesis-related cytokines (EGF and IGF-1) were identified in P-PDL-CM. The expression levels of immune-response-related cytokines (interleukins I, II, and IV) and secreted proteins related to tissue degradation and catalytic activities (matrix metallopeptidase 1 (MMP1), Proteasome subunit, alpha type, 1 (PSMA1), and cullin 7 (CUL7)) were higher in D-PDL-CM. Vasorin (VASN) was expressed more strongly in P-PDL-CM, but tudor domain containing 7 (TDRD7) was expressed more strongly in D-PDL-CM in Western blot analysis.

CONCLUSION

The cytokine expressions of the two cell types showed different patterns, especially in neurogenesis and immune responses. P-PDL cells are more suitable candidates for applications in regenerative therapies.

Tooth-derived stem cells: Update and perspectives

Tissue engineering is an emerging field of science that focuses on creating suitable conditions for the regeneration of tissues. The basic components for tissue engineering involve an interactive triad of scaffolds, signaling molecules, and cells. In this context, stem cells (SCs) present the characteristics of self-renewal and differentiation capacity, which make them promising candidates for tissue engineering. Although they present some common markers, such as cluster of differentiation (CD)105, CD146 and STRO-1, SCs derived from various tissues have different patterns in relation to proliferation, clonogenicity, and differentiation abilities in vitro and in vivo. Tooth-derived tissues have been proposed as an accessible source to obtain SCs with limited morbidity, and various tooth-derived SCs (TDSCs) have been isolated and characterized, such as dental pulp SCs, SCs from human exfoliated deciduous teeth, periodontal ligament SCs, dental follicle progenitor cells, SCs from apical papilla, and periodontal ligament of deciduous teeth SCs. However, heterogeneity among these populations has been observed, and the best method to select the most appropriate TDSCs for regeneration approaches has not yet been established. The objective of this review is to outline the current knowledge concerning the various types of TDSCs, and discuss the perspectives for their use in regenerative approaches.

Periodontal ligament stem cells: current status, concerns, and future prospects

Periodontal ligament stem cells (PDLSCs), which reside in the perivascular space of the periodontium, possess characteristics of mesenchymal stem cells and are a promising tool for periodontal regeneration. Recently, great progress has been made in PDLSC transplantation. Investigators are attempting to maximize the proliferation and differentiation potential of PDLSCs by modifying culture conditions and applying growth factors. Nevertheless, problems remain. First, incomparability among different studies must be minimized by establishing standard guidelines for culture and identification of PDLSCs. Notably, attention should be paid to the biological safety of PDLSC transplantation. The present review updates the latest findings regarding PDLSCs and discusses standard criteria for culture and identification of PDLSCs. Finally, the review calls for careful consideration of PDLSC transplantation safety.

Exposure to a continuous low dose of tetrachlorodibenzo-p-dioxin impairs the development of the tooth root in lactational rats and alters the function of apical papilla-derived stem cells

OBJECTIVES

Ubiquitous environmental pollutants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) cause abnormalities in reproduction and development. TCDD inhibits the development of teeth, and its effects depend on its dose and the developmental stage of the tooth. Our aim here was to investigate the effect of lower doses of TCDD on the development of the tooth root in vivo and in vitro.

DESIGN

We observed tooth root development in lactational rats exposed to continuous low doses of TCDD starting on postnatal day 6 using Mico-CT analyses and histopathological examinations. And then the characteristics of stem cells derived from the apical papilla (SCAPs) were evaluated and compared with SCAPs induced by lower doses of TCDD both in vitro and in vivo.

RESULTS

The results of experiments showed that rat pups exposed to low dose TCDD at prenatal stage developed, dentine hypoplasia, and hypomineralization. Further, TCDD impaired the functions of SCAPs in vivo by inhibiting cell proliferation and osteogenic and odontogenic differentiation. The impairment of SCAPs after TCDD exposure was accompanied by increased expression of AHR, down-regulation of the expression of Runx2, and alkaline phosphatase, suggesting that the AHR pathway mediated the effects of TCDD.

CONCLUSION

These results provide the first insights into the toxicity of TCDD, which adversely affects the development of the tooth root through indirectly altering the function of SCAPs.

Today prospects for tissue engineering therapeutic approach in dentistry

In dental practice there is an increasing need for predictable therapeutic protocols able to regenerate tissues that, due to inflammatory or traumatic events, may suffer from loss of their function. One of the topics arising major interest in the research applied to regenerative medicine is represented by tissue engineering and, in particular, by stem cells. The study of stem cells in dentistry over the years has shown an exponential increase in literature. Adult mesenchymal stem cells have recently been isolated and characterized from tooth-related tissues and they might represent, in the near future, a new gold standard in the regeneration of all oral tissues. The aim of our review is to provide an overview on the topic reporting the current knowledge for each class of dental stem cells and to identify their potential clinical applications as therapeutic tool in various branches of dentistry.

In vitro and in vivo characteristics of stem cells from human exfoliated deciduous teeth obtained by enzymatic disaggregation and outgrowth

OBJECTIVE

Stem cells from human exfoliated deciduous teeth (SHED) are a good source of dental tissue for regeneration therapy, and can be obtained using different primary culture methods. The aim of this study was to determine the differences in the in vitro and in vivo characteristics between SHED isolated via enzymatic disaggregation (e-SHED) and outgrowth (o-SHED) primary culture methods.

DESIGN

Dental pulp stem cells were isolated from 14 exfoliated deciduous teeth by enzymatic disaggregation (n=7) and outgrowth (n=7). Their proliferation potential and colony-forming ability were evaluated in vitro, as was their mesenchymal stem-cell-marker expression (using flow cytometry), and their differentiation was verified using quantitative real-time PCR (qPCR) and histochemical staining. In addition, the qualitative and quantitative characteristics of the hard tissue that was generated after in vivo transplantation were compared using haematoxylin and eosin staining, immunohistochemical staining, qPCR, and quantitative alkaline phosphatase analysis.

RESULTS

The cell-proliferation potential, colony-forming ability, and Stro-1 and CD146 expression were higher in e-SHED than in o-SHED. While the in vitro adipogenic differentiation potential was greater in e-SHED than in o-SHED, the in vitro osteogenic differentiation did not differ significantly between the two cell types. Although in vivo hard tissue formation was greater following transplantation of o-SHED into mice, there was no difference in the quality of hard tissue generated by e-SHED and o-SHED.

CONCLUSION

The findings of this study indicate that e-SHED exhibit stronger stemness characteristics, but that o-SHED are more suitable for hard-tissue regeneration therapy in teeth.

Tissue engineering in dentistry

OBJECTIVES

of this review is to inform practitioners with the most updated information on tissue engineering and its potential applications in dentistry.

DATA

The authors used "PUBMED" to find relevant literature written in English and published from the beginning of tissue engineering until today. A combination of keywords was used as the search terms e.g., "tissue engineering", "approaches", "strategies" "dentistry", "dental stem cells", "dentino-pulp complex", "guided tissue regeneration", "whole tooth", "TMJ", "condyle", "salivary glands", and "oral mucosa".

SOURCES

Abstracts and full text articles were used to identify causes of craniofacial tissue loss, different approaches for craniofacial reconstructions, how the tissue engineering emerges, different strategies of tissue engineering, biomaterials employed for this purpose, the major attempts to engineer different dental structures, finally challenges and future of tissue engineering in dentistry.

STUDY SELECTION

Only those articles that dealt with the tissue engineering in dentistry were selected.

CONCLUSIONS

There have been a recent surge in guided tissue engineering methods to manage periodontal diseases beyond the traditional approaches. However, the predictable reconstruction of the innate organisation and function of whole teeth as well as their periodontal structures remains challenging. Despite some limited progress and minor successes, there remain distinct and important challenges in the development of reproducible and clinically safe approaches for oral tissue repair and regeneration. Clearly, there is a convincing body of evidence which confirms the need for this type of treatment, and public health data worldwide indicates a more than adequate patient resource. The future of these therapies involving more biological approaches and the use of dental tissue stem cells is promising and advancing. Also there may be a significant interest of their application and wider potential to treat disorders beyond the craniofacial region.

CLINICAL SIGNIFICANCE

Considering the interests of the patients who could possibly be helped by applying stem cell-based therapies should be carefully assessed against current ethical concerns regarding the moral status of the early embryo.