Stem cells and future periodontal regeneration

Gastrointestinal cholecystokinin signaling pathway drugs modulate osteogenic/cementogenic differentiation of human periodontal ligament stem cells

OBJECTIVES

Understanding the complexities of periodontal regeneration, particularly the unpredictable osteogenic/cementogenic differentiation of low-potential PDLSCs (LOP-PDLSCs), remains challenging. Identifying new therapeutic targets is crucial for enhancing regeneration. This study investigates the modulation of the Cholecystokinin (CCK) pathway, a key signaling cascade with roles in the gastrointestinal system, as a potential osteogenic/cementogenic pathway in PDLSCs.

METHODS

Gastrointestinal CCK-related drugs, Lorglumide and Sincalide, were tested for their effects on mineralization in PDLSCs. Lorglumide blocked the CCK pathway in high-potential PDLSCs (HOP-PDLSCs), while Sincalide enhanced mineralization in low-potential PDLSCs (LOP-PDLSCs). Cellular viability was tested under different drug concentrations, followed by a mineralization assay (AR-S) using non-toxic doses. RT-qPCR for osteogenic-related genes (IGF1, OCN, RUNX2) and CCK pathway-related genes (CCK, CCKAR, CCKBR, COX2, FOS, JNK3, RGS2) assessed gene modulation. Alkaline phosphatase (ALP) activity, Ca²⁺ quantification, and IP3 receptor phosphorylation were also evaluated.

RESULTS

Lorglumide reduced mineralization, ALP activity, and RUNX2, OCN, and IGF1 transcripts in HOP-PDLSCs (p < 0.05). It decreased CCK and CCKAR expression, modulated COX2, FOS, JNK3, and RGS2 genes, reduced IP3 receptor phosphorylation, and lowered calcium levels (p < 0.05). Conversely, Sincalide enhanced mineralization in LOP-PDLSCs, increasing ALP activity and OCN and IGF1 expression (p < 0.05). It upregulated COX2, FOS, JNK3, and RGS2 genes, phosphorylated IP3 receptors in LOP1, and increased calcium levels in all LOP-PDLSCs (p < 0.05).

CONCLUSIONS

Sincalide and Lorglumide modulate PDLSCs' osteogenesis/cementogenesis, revealing the complex interplay of gastrointestinal drugs in periodontal tissue regeneration and offering insights for innovative therapies.

CLINICAL SIGNIFICANCE

This study demonstrates the potential of gastrointestinal drugs targeting the CCK signaling pathway as innovative modulators for periodontal regeneration. By regulating osteogenic/cementogenic differentiation in hPDLSCs, these findings may pave the way for the development of novel biomaterials and therapies, promising improved outcomes in periodontal tissue regeneration for clinical applications.

MicroRNA functions in osteogenic differentiation of periodontal ligament stem cells: a scoping review

This scoping review aimed to describe the differential microRNA (miRNA) functions in osteogenic differentiation of periodontal ligament stem cells (PDLSCs), and then analyze the potential of applying PDLSCs and miRNAs in bone regeneration. The databases of PubMed, Google Scholar and EBSCO search were performed by the 4 themes, including periodontal ligament stem cells, miRNA, osteogenic differentiation, and tissue regeneration. The original articles described miRNA functions in osteogenic differentiation of PDLSCs were identified and selected for content analyze. The articles suggested that PDLSCs have high potential in bone regeneration because of their multipotency and immunomodulation. PDLSCs are conveniently accessible and obtained from extracted teeth. However, recent evidence reported that PDLSCs of various origins demonstrate differential characteristics of osteogenic differentiation. Exosomal miRNAs of PDLSCs demonstrate a regulatory role in tissue regeneration. The properties of PDLSCs associated to miRNA functions are altered in differential microenvironmental conditions such as infection, inflammation, high-glucose environment, or mechanical force. Therefore, these factors must be considered when inflamed PDLSCs are used for tissue regeneration. The results suggested inflammation-free PDLSCs harvested from the middle third of root surface provide the best osteogenic potential. Alternatively, the addition of miRNA as a bioactive molecule also increases the success of PDLSCs therapy to enhance their osteogenic differentiation. In conclusion, Exosome-derived miRNAs play a key role in PDLSCs osteogenic differentiation during tissue regeneration. While the success of PDLSCs in tissue regeneration could be uncertain by many factors, the use of miRNAs as an adjunct is beneficial for new bone regeneration.

Therapeutic effect of mesenchymal stem cell-derived exosome therapy for periodontal regeneration: a systematic review and meta-analysis of preclinical trials

BACKGROUND

To assess the therapeutic effects of mesenchymal stem cell (MSC)-derived exosome therapy on periodontal regeneration and identify treatment factors associated with enhanced periodontal regeneration in recent preclinical studies.

METHODS

Searches were conducted in PubMed, Cochrane Library, EMBASE, and Web of Science databases until October 10, 2024. A risk of bias (ROB) assessment was performed using the SYRCLE tool. Osteogenic-related parameters were used as the primary outcome measures.

RESULTS

In total, 1360 articles were identified, of which 17 preclinical studies were based on MSC-derived exosome therapy, and they demonstrated a beneficial effect on BV/TV (SMD = 13.99; 95% Cl = 10.50, 17.48; p < 0.00001), CEJ-ABC (SMD = -0.22; 95% Cl = -0.31, -0.13; p < 0.00001), BMD (SMD = 0.29; 95% Cl = 0.14, 0.45; p = 0.0002), and Tp.Sp (SMD = -0.08; 95% Cl= -0.15, -0.02; p = 0.02) compared with the control group. However, no significant differences were observed in Tp.Th (SMD = 0.03; 95% CI = 0.00, 0.07; p = 0.09) between the exosome-treated group and control group. Additionally, subgroup analysis indicated that preconditioned exosomes (p = 0.03) significantly improved BV/TV. In contrast, there were no significant differences in the enhancement of BV/TV with respect to the application method (p = 0.29), application frequency (p = 0.10), treatment duration (p = 0.15), or source of MSCs (p = 0.31).

CONCLUSIONS

MSC-derived exosomes show great promise for enhancing the quality of periodontal regeneration. However, more standardized and robust trials are needed to reduce heterogeneity and bias across studies and to confirm the therapeutic parameters associated with the enhancement of periodontal regeneration by MSC-derived exosomes.

REGISTRATION

CRD42024546236.

Nicotine destructs dental stem cell-based periodontal tissue regeneration

Background/purpose

Nicotine is a widely known addictive and toxic substance in cigarette that exacerbates periodontitis. However, its deleterious effects on dental stem cells and subsequent implications in tissue regeneration remain unclear. This study aimed to explore the effects of nicotine on the regenerative capacity of human periodontal ligament stem cells (hPDLSCs) based on transcriptomics and proteomics, and determined possible targeted genes associated with smoking-related periodontitis.

Materials and methods

hPDLSCs were treated with different concentrations of nicotine ranging from 10-3 to 10-8 M. Transcriptomics and proteomics were performed and confirmed employing Western blot, 5-ethynyl-2'-deoxyuridine (EdU), and alkaline phosphatase (ALP) staining. A ligature-induced periodontitis mouse model was established and administrated with nicotine (16.2 μg/10 μL) via gingival sulcus. The bone resorption was assessed by micro-computed tomography and histological staining. Key genes were identified using multi-omics analysis with verifications in hPDLSCs and human periodontal tissues.

Results

Based on enrichments analysis, nicotine-treated hPDLSCs exhibited decreased proliferation and differentiation abilities. Local administration of nicotine in mouse model significantly aggravated bone resorption and undermined periodontal tissue regeneration by inhibiting the endogenous dental stem cells regenerative ability. HMGCS1, GPNMB, and CHRNA7 were hub-genes according to the network analysis and corelated with proliferation and differentiation capabilities, which were also verified in both cells and tissues.

Conclusion

Our study investigated the destructive effects of nicotine on the regeneration of periodontal tissues from aspects of in vitro and in vivo with the supporting information from both transcriptome and proteome, providing novel targets into the molecular mechanisms of smoking-related periodontitis.

The Osteogenic Role of Biomaterials Combined with Human-Derived Dental Stem Cells in Bone Tissue Regeneration

The use of stem cells in regenerative medicine had great potential for clinical applications. However, cell delivery strategies have critical importance in stimulating the differentiation of stem cells and enhancing their potential to regenerate damaged tissues. Different strategies have been used to investigate the osteogenic potential of dental stem cells in conjunction with biomaterials through in vitro and in vivo studies. Osteogenesis has a broad implication in regenerative medicine, particularly for maxillofacial defects. This review summarizes some of the most recent developments in the field of tissue engineering using dental stem cells.

Mitochondria transfer reverses the inhibitory effects of low stiffness on osteogenic differentiation of human mesenchymal stem cells

Microenvironment biophysical factors such as matrix stiffness can noticeably affect the differentiation of mesenchymal stem cells (MSCs). In this mechanobiology transduction process, mitochondria are shown to be an active participant. The present study aims to systematically elucidate the phenotypic and functional changes of mitochondria during the stiffness-mediated osteogenic differentiation. Additionally, the effect of mitochondria transfer on the osteogenesis of impaired MSCs caused by stiffness was investigated. Human periodontal ligament stem cells (PDLSCs) were used as model cells in the current study. Low stiffness restrained the cell spreading and significantly inhibited the proliferation and osteogenic differentiation of PDLSCs. Mitochondria of PDLSCs cultured on low stiffness exhibited shorter length, rounded shape, fusion/fission imbalance, ROS and mitophagy level increase, and ATP production reduction. The inhibited mitochondria function and osteogenic differentiation capacity were recovered to near-normal levels after transferring the mitochondria of PDLSCs cultured on the high stiffness. This study indicated that low matrix stiffness altered the mitochondrial morphology and induced systematical mitochondrial dysfunction during the osteogenic differentiation of MSCs. Mitochondria transfer was proved to be a feasible technique for maintaining MSCs function in vitro by reversing the osteogenesis ability.

Influence of Ascorbic Acid as a Growth and Differentiation Factor on Dental Stem Cells Used in Regenerative Endodontic Therapies

BACKGROUND

Vitamin C is one of the major extracellular nonenzymatic antioxidants involved in the biosynthesis of collagen. It promotes the growth of fibroblasts, wound healing processes, and enhances the survival and differentiation of osteoblasts. The potential effects of ascorbic acid on human dental pulp cells (DPC) and the cells of the apical papilla (CAP) used in actual regenerative endodontic procedures remain largely unknown. In this study, we investigated the possible employment of ascorbic acid in the differentiation and regenerative therapies of DPC and CAP.

METHODS

Nine extracted human wisdom teeth were selected for this study. Subpopulations of stem cells within DPC and CAP were sorted with the mesenchymal stem cell marker STRO-1, followed by treatments with different concentrations (0 mM, 0.1 mM, 0.5 mM, and 1.0 mM) of ascorbic acid (AA), RT-PCR, and Western blot analysis.

RESULTS

FACS analysis revealed the presence of cell subpopulations characterized by a strong expression of mesenchymal stem cell marker STRO-1 and dental stem cell markers CD105, CD44, CD146, CD90, and CD29. Treatment of the cells with defined amounts of AA revealed a markedly increased expression of proliferation marker Ki-67, especially in the concentration range between 0.1 mM and 0.5 mM. Further investigations demonstrated that treatment with AA led to significantly increased expression of common stem cell markers OCT4, Nanog, and Sox2. The most potent proliferative and expressional effects of AA were observed in the concentration of 0.1 mM.

CONCLUSIONS

AA might be a novel and potent growth promoter of human dental cells. Increasing the properties of human dental pulp cells and the cells of the apical papilla using AA could be a useful factor for further clinical developments of regenerative endodontic procedures.

Therapeutic and Metagenomic Potential of the Biomolecular Therapies against Periodontitis and the Oral Microbiome: Current Evidence and Future Perspectives

The principles of periodontal therapy are based on the control of microbial pathogens and host factors that contribute to biofilm dysbiosis, with the aim of modulating the progression of periodontitis and periodontal tissue destruction. It is currently known how differently each individual responds to periodontal treatment, depending on both the bacterial subtypes that make up the dysbiotic biofilm and interindividual variations in the host inflammatory response. This has allowed the current variety of approaches for the management of periodontitis to be updated by defining the goals of target strategies, which consist of reducing the periodontopathogenic microbial flora and/or modulating the host-mediated response. Therefore, this review aims to update the current variety of approaches for the management of periodontitis based on recent target therapies. Recently, encouraging results have been obtained from several studies exploring the effects of some targeted therapies in the medium- and long-term. Among the most promising target therapies analyzed and explored in this review include: cell-based periodontal regeneration, mediators against bone resorption, emdogain (EMD), platelet-rich plasma, and growth factors. The reviewed evidence supports the hypothesis that the therapeutic combination of epigenetic modifications of periodontal tissues, interacting with the dysbiotic biofilm, is a key step in significantly reducing the development and progression of disease in periodontal patients and improving the therapeutic response of periodontal patients. However, although studies indicate promising results, these need to be further expanded and studied to truly realize the benefits that targeted therapies could bring in the treatment of periodontitis.

Expression of Wnt signaling agonists and antagonists in periodontitis and healthy subjects, before and after non-surgical periodontal treatment: A systematic review

Periodontitis is a preventable and treatable multifactorial chronic inflammatory disease that can lead to irreversible periodontal destruction and tooth loss. Wnt signaling and its regulators play an important role in periodontal inflammation, destruction, regeneration, and reconstruction. This systematic review aimed at investigating the involvement of Wnt signaling agonists and antagonists in periodontitis and healthy subjects, before and after periodontal treatment. Electronic searches were carried out using MEDLINE/PubMed, EMBASE, and Cochrane Library databases in addition to hand searches. Studies having different designs assessing the levels of Wnt signaling antagonist and agonist levels in gingival crevicular fluid, serum, and tissue in patients diagnosed with periodontitis or gingivitis, compared with healthy individuals were included. In addition, studies compared these levels in periodontitis patients before and after non-surgical periodontal therapy were also eligible. Sixteen studies met the eligibility criteria. Sclerostin (SOST) has been mainly investigated in the literature (8 publications). Sclerostin (5 studies), Wnt-5a (2 studies), secreted frizzled-related protein 1 (SFRP1) (3 studies), and β-catenin (3 studies) show increased levels in periodontitis compared with periodontal health. Strong correlations between marker levels and periodontal clinical parameters were identified for SOST (5 studies), SFRP1 (2 studies), and β-catenin (2 studies). SOST (3 studies) and SFRP1 (1 study) levels significantly decrease following non-surgical periodontal treatment. The present systematic review demonstrated an association between Wnt signaling agonist and antagonist levels and periodontitis. Wnt agonists and antagonists may serve as valuable diagnostic and prognostic markers for periodontitis onset and progression. Further case-control and longitudinal studies should be conducted for different Wnt signaling agonists and antagonists.

An Up-To-Date Overview of Dental Tissue Regeneration Using Dental Origin Mesenchymal Stem Cells: Challenges and Road Ahead

Stem cells (SCs) research has experienced exponential growth in recent years. SC-based treatments can enhance the lives of people suffering from cardiac ischemia, Alzheimer’s disease, and regenerative drug conditions, like bone or loss of teeth. Numerous kinds of progenitor/SCs have been hypothesized to depend on their potential to regain and/or heal wounded tissue and partly recover organ function. Growing data suggest that SCs (SCs) are concentrated in functions and that particular tissues have more SCs. Dental tissues, in particular, are considered a significant cause of mesenchymal stem cells (MSCs) cells appropriate for tissue regeneration uses. Tissue regeneration and SCs biology have particular attention in dentistry because they may give a novel method for creating clinical material and/or tissue redevelopment. Dental pulp, dental papilla, periodontal ligament, and dental follicle contain mesenchymal SCs. Such SCs, which must be identified and cultivated in specific tissue culture environments, may be used in tissue engineering applications such as tooth tissue, nerve regeneration, and bone redevelopment. A new cause of SCs, induced pluripotent SCs, was successfully made from human somatic cells, enabling the generation of the patient and disease-specific SCs. The dental SC’s (DSCs) multipotency, rapid proliferation rate, and accessibility make it an ideal basis of MSC for tissue redevelopment. This article discusses current advances in tooth SC investigation and its possible application in tissue redevelopment.

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.

Meeting the challenges and clinical requirements for dental regeneration; the New Zealand experience

Disease and trauma leading to tooth loss and destruction of supporting bone is a significant oral handicap, which may be addressed through surgical therapies that aim to regenerate the lost tissue. Whilst complete regeneration of teeth is still aspirational, regeneration of supporting structures (dental pulp, cementum, periodontal ligament, bone) is becoming commonplace, both for teeth and for titanium dental implants that are used to replace teeth. Most grafting materials are essentially passive, however the next generation of oral regenerative devices will combine non-antibiotic antimicrobials and/or osteogenic or inductive factors and/or appropriate multipotential stem cells. The review gives an overview of the approaches taken, including fabrication of novel scaffolds, incorporation of growth factors and cell-based therapies, and discusses the preclinical animal models we employ in the development pathway.

Potential of Bone-Marrow-Derived Mesenchymal Stem Cells for Maxillofacial and Periodontal Regeneration: A Narrative Review

Bone-marrow-derived mesenchymal stem cells (BM-MSCs) are one of the most widely studied postnatal stem cell populations and are considered to utilize more frequently in cell-based therapy and cancer. These types of stem cells can undergo multilineage differentiation including blood cells, cardiac cells, and osteogenic cells differentiation, thus providing an alternative source of mesenchymal stem cells (MSCs) for tissue engineering and personalized medicine. Despite the ability to reprogram human adult somatic cells to induced pluripotent stem cells (iPSCs) in culture which provided a great opportunity and opened the new door for establishing the in vitro disease modeling and generating an unlimited source for cell base therapy, using MSCs for regeneration purposes still have a great chance to cure diseases. In this review, we discuss the important issues in MSCs biology including the origin and functions of MSCs and their application for craniofacial and periodontal tissue regeneration, discuss the potential and clinical applications of this type of stem cells in differentiation to maxillofacial bone and cartilage in vitro, and address important future hopes and challenges in this field.

Safety and Efficacy Results of BonoFill First-in-Human, Phase I/IIa Clinical Trial for the Maxillofacial Indication of Sinus Augmentation and Mandibular Bone Void Filling

PURPOSE

The gold standard for bone regeneration of bone deficiencies is still an autologous bone graft, which has considerable disadvantages; namely, the need for a second major surgery and the limited volume of bone available for harvesting. BonoFill (BF) is a novel, tissue-engineered, bone graft with intrinsic osteoinductive, osteoconductive, and osteogenic properties, consisting of the patient's own adipose tissue-derived mesenchymal stem cells, attached to hydroxyapatite particles. Here, we present the safety and efficacy results of BF first-in-human clinical study for maxillofacial bone tissue regeneration.

MATERIALS AND METHODS

Eleven eligible male and female subjects, aged 49-65 years, were enrolled into the clinical study in 2 clinical indications: Bone augmentation and bone void grafting in the jaws. Clinical follow-up was performed throughout a period of 6 months after BF treatment and included clinical examination, blood tests, CT scans, and biopsies collected from the transplantation site to assess chronic bone infection, changes in complete blood count, and adequate bone augmentation for implant placement.

RESULTS

The study results demonstrated that BF promoted adequate bone tissue regeneration without complications. Per our evaluation, there were no incidents of chronic bone infection, or significant changes in complete blood count, and the patients reported overall good health for the duration of the study. At trial end, in the sinus augmentation indication, the BF treated sites residual bone was augmented at an average of 6.36 mm (Δ new bone, n = 10) and the total bone height at the treated area was on average 11.44 mm (n = 10). In the indication of filling of bone voids, the patient's average residual bone height of 2.91 mm was 15.76 mm (n = 1) at trial end.

CONCLUSIONS

BF treatment was shown to be safe and resulted in newly generated bone, which provided adequate bone height for placement of dental implants. Thus, BF is a promising novel autologous bone graft for bone tissue repair.

Dual-Functionalized Apatite Nanocomposites with Enhanced Cytocompatibility and Osteogenesis for Periodontal Bone Regeneration

The development of biomimetic bone graft materials for periodontal tissue engineering is a field of topical interest. In this study, we designed a dual-functionalized apatite nanocomposite, which could integrate multiple molecular cues for manipulating the fate of periodontal ligament stem cells (PDLSCs). Briefly, inspired by mussels, a biomimetic nanohydroxyapatite was fabricated using a polydopamine structure as a template (named as tHA) and then surface-modified with bone-forming peptide-1 (BFP-1) and vascular endothelial growth factor-mimicking peptide (QK) via a single step of catechol chemistry. Our study showed that the biofunctions of tethered peptides were not compromised on the surface of apatite nanoparticles. Because of the synergistic effect of BFP-1 and QK peptides, the dual-functionalized apatite nanocomposite showed improved cytocompatibility compared to controls. Moreover, it can boost the proliferation and osteogenic differentiation of PDLSCs, indicating excellent bioactivity of tHA-BFP/QK nanoparticles on cell fate decision. More importantly, animal experiments showed that dual-functionalized apatite nanocomposites could dramatically promote the regeneration of periodontal bone. It is concluded that our work provides an instructive insight into the design of biomimetic apatite nanocomposites, which holds a great potential for applications in periodontal bone repair.

Periodontal regeneration: a bibliometric analysis of the most influential studies

Aim: The aim of the present study is to identify the most influential research articles and their main characteristics in the specialty of periodontal regeneration. Materials & methods: The Web of Science database advance search was performed in the subject category of 'Dentistry, Oral surgery and medicine' from January 2004 to October 2018 to retrieve citations data. Results: The majority of the articles were published in journals dedicated to the specialty of periodontology. Among the top-cited articles most emphasized study types were randomized control trials (n = 25) and reviews (n = 20). Conclusion: The present bibliometric analysis provides comprehensive information regarding the contributions made in the advancement of regenerative periodontal research. The authors from developed countries and affiliated with interdisciplinary/multicenter institutions have predominantly contributed.

Cellular therapy in periodontal regeneration

Periodontitis is a chronic inflammatory condition leading to destruction of the tooth supporting tissues, which if left untreated may cause tooth loss. The treatment of periodontitis mainly aims to arrest the inflammatory process by infection control measures, although in some specific lesions a limited periodontal regeneration can also be attained. Current regenerative approaches are aimed to guide the cells with regenerative capacity to repopulate the lesion and promote new cementum and new connective tissue attachment. The first phase in periodontal tissue regeneration involves the differentiation of mesenchymal cells into cementoblasts to promote new cementum, thus facilitating the attachment of new periodontal ligament fibers to the root and the alveolar bone. Current regenerative approaches limit themselves to the confines of the lesion by promoting the self-regenerative potential of periodontal tissues. With the advent of bioengineered therapies, several studies have investigated the potential use of cell therapies, mainly the use of undifferentiated mesenchymal cells combined with different scaffolds. The understanding of the origin and differentiation patterns of these cells is, therefore, important to elucidate their potential therapeutic use and their comparative efficacy with current technologies. This paper aims to review the in vitro and experimental studies using cell therapies based on application of cementoblasts and mesenchymal stem cells isolated from oral tissues when combined with different scaffolds.

Periodontal healing using a collagen matrix with periodontal ligament progenitor cells in a dehiscence defect model in beagle dogs

Purpose

To histologically characterize periodontal healing at 8 weeks in surgically created dehiscence defects in beagle dogs that received a collagen matrix with periodontal ligament (PDL) progenitor cells.

Methods

The bilateral maxillary premolars and first molars in 6 animals were used. Standardized experimental dehiscence defects were made on the buccal side of 3 premolars, and primary culturing of PDL progenitor cells was performed on the molars. Collagen matrix was used as a scaffold and a delivery system for PDL progenitor cells. The experimental sites were grafted with collagen matrix (COL), PDL progenitor cells with collagen matrix (COL/CELL), or left without any material (CTL). Histologic and histomorphometric analyses were performed after 8 weeks.

Results

The defect height from the cementoenamel junction to the most apical point of cementum removal did not significantly differ across the CTL, COL, and COL/CELL groups, at 4.57±0.28, 4.56±0.41, and 4.64±0.27 mm (mean ± standard deviation), respectively; the corresponding values for epithelial adhesion were 1.41±0.51, 0.85±0.29, and 0.30±0.41 mm (P<0.05), the heights of new bone regeneration were 1.32±0.44, 1.65±0.52, and 1.93±0.61 mm (P<0.05), and the cementum regeneration values were 1.15±0.42, 1.81±0.46, and 2.57±0.56 mm (P<0.05). There was significantly more new bone formation in the COL/CELL group than in the CTL group, and new cementum length was also significantly higher in the COL/CELL group. However, there were no significant differences in the width of new cementum among the groups.

Conclusions

PDL progenitor cells carried by a synthetic collagen matrix may enhance periodontal regeneration, including cementum and new bone formation.

A minimally invasive transfer method of mesenchymal stem cells to the intact periodontal ligament of rat teeth: a preliminary study

The aim of this study was to introduce a minimally invasive procedure for mesenchymal stem cell (MSC) transfer into the intact periodontal ligament (PDL) of the molar teeth in rats. Ten 12-week-old Wistar albino rats were used for this preliminary study. MSCs were obtained from bones of two animals and were labeled with green fluorescent protein (GFP). Four animals were randomly selected for MSC injection, while 4 animals served as a control group. Samples were prepared for histological analysis, Cox-2 mRNA expression polymerase chain reaction analysis, and fluorescent microscopy evaluation. The number of total cells, number of osteoclastic cells, and Cox-2 mRNA expression levels of the periodontal tissue of teeth were calculated. The number of total cells was increased with MSC injections in PDL significantly (P < 0.001). The number of osteoclastic cells and Cox-2 mRNA expression were found to be similar for the two groups. GFP-labeled MSCs were observed with an expected luminescence on the smear samples of the PDL with transferred MSCs. The results of this preliminary study demonstrate successful evidence of transferring MSCs to intact PDL in a nonsurgical way and offer a minimally invasive procedure for transfer of MSCs to periodontal tissues.

Exendin-4 relieves the inhibitory effects of high glucose on the proliferation and osteoblastic differentiation of periodontal ligament stem cells

BACKGROUND

With the impaired regenerative potential in patients with diabetes mellitus (DM), Periodontal ligament stem cells (PDLSCs) are regarded as an attractive source of stem cells for periodontal cytotherapy. Recent studies have shown that Exendin-4 (Ex-4) exerts cell-protective effects and bone remodeling ability on many types of cells. The aim of this study was to investigate whether Ex-4 alleviates the inhibition of high glucose on the proliferation and osteogenic differentiation of PDLSCs.

METHODS

PDLSCs were incubated in medium supplemented with 5.5 mM d-glucose (NG), 30 mM d-glucose (HG), NG plus Ex-4, and HG plus different concentration (1, 10, 20, 100 nM) of Ex-4 respectively. Cell proliferation was detected by CCK-8 assay and cell cycle analysis. Osteogenesis was assessed by Alizarin Red S staining and evaluation of the mRNA expression of Runx2, ALP and Osx at day 7, 14 and 21. Intracellular level of reactive oxygen species (ROS) was detected using 5-(and-6)-chloromethyl-2',7'-dichlorodihydro-fluorescein diacetate (CMH2DCF-DA).

RESULTS

The proliferation ability, mineralized nodules forming capacity and the mRNA expression of Runx2, ALP and Osx of PDLSCs in HG group were decreased, the ROS level was increased compared to NG group. With the treatment of Ex-4, the HG-inhibited proliferation ability and osteogenic differentiation ability of PDLSCs were significantly reversed, the HG-increased ROS level could be down-regulated. Moreover, Ex-4 enhanced the osteogenic differentiation of normal PDLSCs.

CONCLUSIONS

Ex-4 alleviates the inhibitory effect of HG on the proliferation and osteoblastic differentiation of PDLSCs, and has a significant enhance in the osteoblastic differentiation of normal PDLSCs, giving new insights into the possible therapeutic method of diabetic periodontitis.

Comparison of Intraoral Bone Regeneration with Iliac and Alveolar BMSCs

This study compared the osteogenic potential of bone marrow mesenchymal stem cells (BMSCs) of iliac and alveolar origins (I-BMSCs and Al-BMSCs, respectively), which were transplanted in combination with β tricalcium phosphate (β-TCP) in peri-implant bone defects to investigate the osseointegration between dental implants and tissue-engineered bone in dogs. Specifically, I-BMSCs and Al-BMSCs were cultured, characterized, and seeded on β-TCP and subjected to immunoblotting analyses and alkaline phosphatase activity assays. Subsequently, these cell-seeded scaffolds were implanted into defects that were freshly generated in the mandibular premolar areas of 4 dogs. The defects were covered with β-TCP + Al-BMSCs ( n = 6), β-TCP + I-BMSCs ( n = 6), or β-TCP ( n = 6) or served as the blank control ( n = 6). After healing for 12 wk, the formation and mineralization of new bones were assessed through micro-computed tomographic, histologic, and histomorphometric analyses, and bone-to-implant contacts were measured in the specimens. It was evident that in this large animal model, I-BMSCs and Al-BMSCs manifested similarly strong osteogenic potential, as significantly more new bone was formed in the Al-BMSC and I-BMSC groups than otherwise ( P < 0.01). Therefore, Al-BMSCs are emerging as an efficient alternative for autologous mesenchymal stem cells in regenerative dental and maxillofacial therapies. I-BMSCs, if not restricted in their bioavailability, can also be of great utility in bone tissue-engineering applications.

Exploring the Gingival Recession Surgical Treatment Modalities: A Literature Review

Gingival recessions present complex soft tissue pathology, with a multiple aetiology and a high prevalence which increases with age. They are defined as an exposure of the root surface of the teeth as a result of the apical migration of the gingival margin beyond the cementum-enamel junction, causing functional and aesthetic disturbances to the affected individuals. Aiming to ensure complete root coverage and satisfying aesthetic outcomes, a wide range of surgical techniques have been proposed through the decades for the treatment of the gingival recessions. The following literature review attempts to provide a comprehensive, structured and up-to-date summary of the relevant literature regarding these surgical techniques, aiming to emphasise for each technique its indications, its long-term success and predictability, its advantages and disadvantages about each other.

Cementum regeneration using stem cells in the dog model: A systematic review

OBJECTIVE

Restoring lost tissues of the periodontium, such as cementum, is essential in reducing the risk of tooth loss due to periodontitis and/or severe root resorption. Stem cell therapy is a regenerative strategy in cementum regeneration. This systematic review aimed to analyze the effect of various stem cells and their transplantation method on cementum regeneration in the dog model.

METHODS

Electronic databases were searched, in addition to performing hand searches and a gray literature search. Titles and abstracts were searched according to the inclusion criteria and full texts were selected to be included in this systematic review. Data was extracted from each article and risk of bias was assessed for individual studies.

RESULTS

Most studies reported that the treatment using a variety of stem cells resulted in significantly greater cementum regeneration.

CONCLUSIONS

Because of variations in additional factors included in each study and varied risk of bias among those studies, the effect of each type of stem cell on cementum regeneration in dogs is difficult to clarify. Additional information needs to be obtained from each study in order to further analyze the individual effect of stem cells on cementum regeneration in dogs.

Human Umbilical Cord MSCs as New Cell Sources for Promoting Periodontal Regeneration in Inflammatory Periodontal Defect

Human periodontal ligament stem cells (hPDLSCs) transplantation represents a promising approach for periodontal regeneration; however, the cell source is limited due to the invasive procedure required for cell isolation. As human umbilical cord mesenchymal stem cells (hUCMSCs) can be harvested inexpensively and inexhaustibly, here we evaluated the regenerative potentials of hUCMSCs as compared with hPDLSCs to determine whether hUCMSCs could be used as new cell sources for periodontal regeneration.

Methods The characteristics of hUCMSCs, including multi-differentiation ability and anti-inflammatory capability, were determined by comparison with hPDLSCs. We constructed cell aggregates (CA) using hUCMSCs and hPDLSCs respectively. Then hPDLSCs-CA and hUCMSCs-CA were combined with β-tricalcium phosphate bioceramic (β-TCP) respectively and their regenerative potentials were determined in a rat inflammatory periodontal defect model.

Results hPDLSCs showed higher osteogenic differentiation potentials than hUCMSCs. Meanwhile, hUCMSCs showed higher extracellular matrix secretion and anti-inflammatory abilities than hPDLSCs. Similar to hPDLSCs, hUCMSCs were able to contribute to regeneration of both soft and hard periodontal tissues under inflammatory periodontitis condition. There were more newly formed bone and periodontal ligaments in hPDLSCs and hUCMSCs groups than in non-cell treated group. Moreover, no significant differences of regenerative promoting effects between hPDLSCs and hUCMSCs were found.

Conclusion: hUCMSCs generated similar promoting effects on periodontal regeneration compared with hPDLSCs, and can be used as new cell sources for periodontal regeneration.

Application of selected scaffolds for bone tissue engineering: a systematic review

PURPOSE

The current systematic review investigated the results of application of some of the most commonly used scaffolds in conjugation with stem cells and growth factors in animal and clinical studies.

METHODS

A comprehensive electronic search was conducted according to the PRISMA guidelines in NCBI PMC and PubMed from January 1970 to December 2015 limited to English language publications with available full texts. In vivo studies in relation to "bone healing," "bone regeneration," and at least one of the following items were investigated: allograft, β-tricalcium phosphate, deproteinized bovine bone mineral, hydroxyapetite/tricalcium phosphate, nanohydroxyapatite, and composite scaffolds.

RESULTS

A total of 1252 articles were reviewed, and 46 articles completely fulfilled the inclusion criteria of this study. The highest bone regeneration has been achieved when combination of all three elements, given scaffolds, mesenchymal stem cells, and growth factors, were used. Among studies being reported in this review, bone marrow mesenchymal stem cells are the most studied mesenchymal stem cells, β-tricalcium phosphate is the most frequently used scaffold, and platelet-rich plasma is the most commonly used growth factor.

CONCLUSION

The current review aimed to inform reconstructive surgeons of how combinations of various mesenchymal stem cells, scaffolds, and growth factors enhance bone regeneration. The highest bone regeneration has been achieved when combination of all three elements, given scaffolds, mesenchymal stem cells, and growth factors, were used.

Declined Expression of Histone Deacetylase 6 Contributes to Periodontal Ligament Stem Cell Aging

BACKGROUND

Identification of regulators for aging-associated stem cell (SC) dysfunctions is a critical topic in SC biology and SC-based therapies. Periodontal ligament stem cell (PDLSC), a kind of dental mesenchymal SC with dental regeneration potential, ages with functional deterioration in both in vivo and ex vivo expansion. However, little is known about regulators for PDLSC aging.

METHODS

Expression changes of a potential regulator for PDLSC aging, histone deacetylase 6 (HDAC6), were evaluated within various models. Senescence-associated phenotypic and functional alternations of PDLSC in loss-of-function models for HDAC6 were examined using HDAC6-specific pharmacologic inhibitors or RNA interference-based knockdown. Involvement of p27Kip1 in HDAC6-associated aging was demonstrated by its acetylation and stability changes along with overexpression or functional inhibition of HDAC6.

RESULTS

Expression of HDAC6 decreased significantly in replicative senescence and induced SC aging models. Loss-of-function experiments suggested that pharmacologic inhibition of deacetylase activity of HDAC6 accelerated PDLSC senescence and impaired its SC activities, which showed reduced osteogenic differentiation and diminished migration capacities. Examination of markers for proliferative exhaustion of SCs revealed that protein level of p27Kip1 was specifically elevated after HDAC6 inhibition. HDAC6 physically interacted with p27Kip1 and could deacetylate p27Kip1. Importantly, acetylation of p27Kip1 was negatively regulated by HDAC6, which correlated with alteration of p27Kip1 protein levels.

CONCLUSION

Data suggest that HDAC6 plays an important role in PDLSC aging, which is dependent, at least partially, on regulation of p27Kip1 acetylation.

Oral Mucosa Harbors a High Frequency of Endothelial Cells: A Novel Postnatal Cell Source for Angiogenic Regeneration

Endothelial progenitor cells/endothelial cells (EPCs/ECs) have great potential to treat pathological conditions such as cardiac infarction, muscle ischemia, and bone fractures, but isolation of EPC/ECs from existing cell sources is challenging due to their low EC frequency. We have isolated endothelial progenitor (EP)-like cells from rat oral mucosa and characterized their yield, immunophenotype, growth, and in vivo angiogenic potential. The frequency of EP-like cells derived from oral mucosa is thousands of folds higher than EPCs derived from donor-match bone marrow samples. EP-like cells from oral mucosa were positive for EC markers CD31, VE-Cadherin, and VEGFR2. Oral mucosa-derived EP-like cells displayed robust uptake of acetylated low-density lipoprotein and formed stable capillary networks in Matrigel. Subcutaneously implanted oral mucosa-derived EP-like cells anastomosed with host blood vessels, implicating their ability to elicit angiogenesis. Similar to endothelial colony-forming cells, EP-like cells from oral mucosa have a significantly higher proliferative rate than human umbilical vein endothelial cells. These findings identify a putative EPC source that is easily accessible in the oral cavity, potentially from discarded tissue specimens, and yet with robust yield and potency for angiogenesis in tissue and organ regeneration.

Periodontal regeneration in swine after cell injection and cell sheet transplantation of human dental pulp stem cells following good manufacturing practice

Background

Periodontitis, one of the most prevalent infectious diseases in humans, results in the destruction of tooth-supporting tissues. The purpose of the present study is to evaluate the effect of cell injection and cell sheet transplantation on periodontal regeneration in a swine model.

Methods

In the present study, human dental pulp stem cells (hDPSCs) were transplanted into a swine model for periodontal regeneration. Twelve miniature pigs were used to generate periodontitis with bone defects of 5 mm in width, 7 mm in length, and 3 mm in depth. hDPSCs were obtained for bone regeneration using cell injection or cell sheet transplantation. After 12 weeks, clinical, radiological, and histological assessments of regenerated periodontal tissues were performed to compare periodontal regeneration treated with xenogeneic cell injection and cell sheet implantation.

Results

Our study showed that translating hDPSCs into this large animal model could significantly improve periodontal bone regeneration and soft tissue healing. After 12 weeks, both the hDPSC sheet treatment and hDPSC injection significantly improved periodontal tissue healing clinically in comparison with the control group. The volume of regenerative bone in the hDPSC sheet group (52.7 ± 4.1 mm³) was significantly larger than in the hDPSC injection group (32.4 ± 5.1 mm³) (P < 0.05). The percentage of bone in the periodontium in the hDPSC injection group was 12.8 ± 4.4 %, while it was 17.4 ± 5.3 % in the hDPSC sheet group (P < 0.05).

Conclusion

Both hDPSC injection and cell sheet transplantation significantly regenerated periodontal bone in swine. The hDPSC sheet had more bone regeneration capacity compared with hDPSC injection.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0362-8) contains supplementary material, which is available to authorized users.

Mesenchymal stem cells with osteogenic potential in human maxillary sinus membrane: an in vitro study

OBJECTIVES

The aim of our study is to prove and validate the existence of an osteogenic progenitor cell population within the human maxillary Schneiderian sinus membrane (hMSSM) and to demonstrate their potential for bone formation.

MATERIALS AND METHODS

Ten hMSSM samples of approximately 2 × 2 cm were obtained during a surgical nasal approach for treatment of chronic rhinosinusitis and were retained for this study. The derived cells were isolated, cultured, and assayed at passage 3 for their osteogenic potential using the expression of Alkaline phosphatase, alizarin red and Von Kossa staining, flow cytometry, and quantitative real-time polymerase chain reaction.

RESULTS

hMSSM-derived cells were isolated, showed homogenous spindle-shaped fibroblast-like morphology, characteristic of mesenchymal progenitor cells (MPCs), and demonstrated very high expression of MPC markers such as STRO-1, CD44, CD90, CD105, and CD73 in all tested passages. In addition, von Kossa and Alizarin red staining showed significant mineralization, a typical feature of osteoblasts. Moreover, alkaline phosphatase (ALP) activity was significantly increased at days 7, 14, 21, and 28 of culture in hMSSM-derived cells grown in osteogenic medium, in comparison to controls. Furthermore, osteogenic differentiation significantly upregulated the transcriptional expression of osteogenic markers such as ALP, Runt-related transcription factor 2 (Runx-2), bone morphogenetic protein (BMP)-2, osteocalcin (OCN), osteonectin (ON), and osteopontin (OPN), confirming that hMSSM-derived cells are of osteoprogenitor origin. Finally, hMSSM-derived cells were also capable of producing OPN proteins upon culturing in an osteogenic medium.

CONCLUSION

Our data showed that hMSSM holds mesenchymal osteoprogenitor cells capable of differentiating to the osteogenic lineage.

CLINICAL RELEVANCE

hMSSM contains potentially multipotent postnatal stem cells providing a promising clinical application in preimplant and implant therapy.

Effect of low-level laser irradiation on proliferation of human dental mesenchymal stem cells; a systemic review

CONTEXT

Identification of factors that enhance the proliferation of human dental mesenchymal stem cells (DMSCs) is vital to facilitate tissue regeneration. The role of low-level laser irradiation (LLLI) on proliferation of human DMSCs has not been well established.

OBJECTIVE

To assess the effect of LLLI on proliferation of human DMSCs when applied in-vitro.

DATA SOURCES

Electronic search of literature was conducted (2000-2016) on PubMed, Web of Science, and Scopus databases. Search terms included low-level light therapy, low-level laser irradiation, low-level light irradiation, LLLT, humans, adolescent, adult, cells, cultured, periodontal ligament, dental pulp, stem cells, dental pulp stem cells, mesenchymal stem cells, periodontal ligament stem cell, deciduous teeth, cell proliferation, adult stem cells, radiation, and proliferation.

RESULTS

The literature search identified 165 studies with 6 being eligible for inclusion; all used diode lasers; 5 studies used InGaAIP diode lasers; 4 used 660nm, and the other two applied 810nm or 980nm wavelength LLLI. The distance between the DMSCs and the laser spot ranged between 0.5mm to 2mm. The time intervals of cell proliferation analysis ranged from 0h to 7days after LLLI. After 660nm LLLI, an increase in the DMSC's proliferation was reported [DMSCs extracted from dental pulp of deciduous teeth (two irradiations, 3J/cm(2), 20mW was more effective than 40mW), adult teeth (two irradiations, 0.5 and 1.0J/cm(2), 30mW), and from adult periodontal ligament (two irradiations, 1.0J/cm(2) was more effective than 0.5J/cm(2), 30mW)]. Similarly, an increase in the proliferation of DMSCs extracted from dental pulp of adult teeth was reported after 810nm LLLI (7 irradiations in 7days, 0.1 and 0.2J/cm(2), 60mW) or 980nm LLLI (single irradiation, 3J/cm(2), 100mW). However, 660nm LLLI in one study did not increase the proliferation of DMSCs (single irradiation, energy densities of 0.05, 0.30, 7, and 42J/cm(2), 28mW).

CONCLUSION

There is limited evidence that in-vitro LLLI (660/810/980nm, with energy densities of 0.1-3J/cm(2)) increases the proliferation of DMSCs. Considering the limited evidence and their method heterogeneity it is difficult to reach a firm conclusion. Further research is necessary to identify the optimal characteristics of the LLLI setting (wave length, energy density, power output, frequency/duration of irradiations, distance between the cells and the laser spot/probe) to increase proliferation of DMSCs, and assess its impact on replicative senescence, as well as determine feasibility of the use in the clinical setting.

Apical Closure in Apexification: A Review and Case Report of Apexification Treatment of an Immature Permanent Tooth with Biodentine

Materials such as calcium hydroxide paste and mineral trioxide aggregate are used in apexification treatment of immature permanent teeth, but the search for improved materials with higher characteristics of biocompatibility results in different materials. Biodentine is a tricalcium silicate cement that possesses adequate handling characteristics and acceptable mechanical and bioactivity properties. This report describes the case of a 9-year-old boy who was referred to the Department of Dental Clinic of Querétaro Autonomous University of Mexico. One month prior the patient had suffered a dental trauma of his upper left central incisor and had been treated by another dentist. The clinical diagnosis was previously initiated therapy and symptomatic apical periodontitis. The treatment was apexification with Biodentine. At follow-ups performed at 3, 6, and 18 months after treatment the tooth was asymptomatic. The cone-beam computed tomography scan at 18-month postoperative follow-up revealed continuity of periodontal ligament space, absence of periapical rarefactions, and a thin layer of calcified tissue formed apical to the Biodentine barrier. On the basis of sealing ability and biocompatibility, apexification treatment with Biodentine was applied in the present case report. The favorable clinical and radiographic outcome in this case demonstrated that Biodentine may be an efficient alternative to the conventional apexification materials.

Treatment of periodontal intrabony defects using autologous periodontal ligament stem cells: a randomized clinical trial

Background

Periodontitis, which progressively destroys tooth-supporting structures, is one of the most widespread infectious diseases and the leading cause of tooth loss in adults. Evidence from preclinical trials and small-scale pilot clinical studies indicates that stem cells derived from periodontal ligament tissues are a promising therapy for the regeneration of lost/damaged periodontal tissue. This study assessed the safety and feasibility of using autologous periodontal ligament stem cells (PDLSCs) as an adjuvant to grafting materials in guided tissue regeneration (GTR) to treat periodontal intrabony defects. Our data provide primary clinical evidence for the efficacy of cell transplantation in regenerative dentistry.

Methods

We conducted a single-center, randomized trial that used autologous PDLSCs in combination with bovine-derived bone mineral materials to treat periodontal intrabony defects. Enrolled patients were randomly assigned to either the Cell group (treatment with GTR and PDLSC sheets in combination with Bio-oss^®) or the Control group (treatment with GTR and Bio-oss^® without stem cells). During a 12-month follow-up study, we evaluated the frequency and extent of adverse events. For the assessment of treatment efficacy, the primary outcome was based on the magnitude of alveolar bone regeneration following the surgical procedure.

Results

A total of 30 periodontitis patients aged 18 to 65 years (48 testing teeth with periodontal intrabony defects) who satisfied our inclusion and exclusion criteria were enrolled in the study and randomly assigned to the Cell group or the Control group. A total of 21 teeth were treated in the Control group and 20 teeth were treated in the Cell group. All patients received surgery and a clinical evaluation. No clinical safety problems that could be attributed to the investigational PDLSCs were identified. Each group showed a significant increase in the alveolar bone height (decrease in the bone-defect depth) over time (p < 0.001). However, no statistically significant differences were detected between the Cell group and the Control group (p > 0.05).

Conclusions

This study demonstrates that using autologous PDLSCs to treat periodontal intrabony defects is safe and does not produce significant adverse effects. The efficacy of cell-based periodontal therapy requires further validation by multicenter, randomized controlled studies with an increased sample size.

Trial Registration

NCT01357785 Date registered: 18 May 2011.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0288-1) contains supplementary material, which is available to authorized users.

Potential for Stem Cell-Based Periodontal Therapy

Periodontal diseases are highly prevalent and are linked to several systemic diseases. The goal of periodontal treatment is to halt the progression of the disease and regenerate the damaged tissue. However, achieving complete and functional periodontal regeneration is challenging because the periodontium is a complex apparatus composed of different tissues, including bone, cementum, and periodontal ligament. Stem cells may represent an effective therapeutic tool for periodontal regeneration due to their plasticity and their ability to regenerate different tissues. This review presents and critically analyzes the available information on stem cell-based therapy for the regeneration of periodontal tissues and suggests new avenues for the development of more effective therapeutic protocols.

Characterization of the osteogenic potential of mesenchymal stem cells from human periodontal ligament based on cell surface markers

Mesenchymal stem cell (MSC)-mediated therapy has been shown to be clinically effective in regenerating tissue defects. For improved regenerative therapy, it is critical to isolate homogenous populations of MSCs with high capacity to differentiate into appropriate tissues. The utilization of stem cell surface antigens provides a means to identify MSCs from various tissues. However, few surface markers that consistently isolate highly regenerative MSCs have been validated, making it challenging for routine clinical applications and making it all the more imperative to identify reliable surface markers. In this study, we used three surface marker combinations: CD51/CD140α, CD271, and STRO-1/CD146 for the isolation of homogenous populations of dental mesenchymal stem cells (DMSCs) from heterogeneous periodontal ligament cells (PDLCs). Fluorescence-activated cell sorting analysis revealed that 24% of PDLCs were CD51⁺/CD140α⁺, 0.8% were CD271⁺, and 2.4% were STRO-1⁺/CD146⁺. Sorted cell populations were further assessed for their multipotent properties by inducing osteogenic and chondrogenic differentiation. All three subsets of isolated DMSCs exhibited differentiation capacity into osteogenic and chondrogenic lineages but with varying degrees. CD271⁺ DMSCs demonstrated the greatest osteogenic potential with strong induction of osteogenic markers such as DLX5, RUNX2, and BGLAP. Our study provides evidence that surface marker combinations used in this study are sufficient markers for the isolation of DMSCs from PDLCs. These results provide important insight into using specific surface markers for identifying homogenous populations of DMSCs for their improved utilization in regenerative medicine.

Autologous Stem Cell Application in Periodontal Regeneration Technique (SAI-PRT) Using PDLSCs Directly From an Extracted Tooth···An Insight

Periodontal regeneration represents the ultimate goal of periodontal therapy. The current regenerative techniques have limited success rates especially in advanced periodontal defects. Currently the research is focused on novel cell-based approaches for periodontal regeneration to overcome the limitations of existing treatment. The human clinical trial on stem cells based periodontal regeneration is promising. The plethora of animal studies provide sound evidence to support the belief that periodontal ligament stem cells (PDLSCs) can be used for periodontal regeneration. The direct application of autologous periodontal stem cells in treatment of intrabony defects is attempted for the first time in periodontal literature. Stem cell Application in Periodontal Regeneration Technique (SAI-PRT) using direct PDLSCs has overcome the limitations and concerns of ex- vivo stem cell culture methods like high cost, technique sensitivity, loss of stemness during cell passage, genetic manipulation and tumorigenic potential. Clinical feasibility, success and cost effectiveness over currently available techniques are encouraging. The clinical utility of this novel idea is recommended.

Characterization of human periodontal ligament cells cultured on three-dimensional biphasic calcium phosphate scaffolds in the presence and absence of L-ascorbic acid, dexamethasone and β-glycerophosphate in vitro

The aim of this study was to evaluate the effect of porous biphasic calcium phosphate (BCP) scaffolds on the proliferation and osteoblastic differentiation of human periodontal ligament cells (hPDLCs) in the presence and absence of osteogenic inducer (L-ascorbic acid, dexamethasone and β-glycerophosphate). The cell growth within the scaffolds in the absence of osteogenic inducers was studied by cell counting kit-8 (CCK-8) assay and scanning electron microscopy (SEM). Alkaline phosphatase (ALP) activity and osteoblastic differentiation markers of hPDLCs in BCP scaffolds were examined in the presence and absence of osteogenic inducers. The cell number of hPDLCs in the BCP scaffolds was less than that of hPDLCs cultured in microplates (control). SEM images showed that cells successfully adhered to the BCP scaffolds and spread amongst the pores; they also produced abundant extracellular cell matrix. In the presence and absence of osteogenic inducers, the ALP activity of hPDLCs within BCP scaffolds was suppressed in varying degrees at all time-points. In the absence of osteogenic inducers, hPDLCs in BCP scaffolds express significant higher levels of osteopontin (OPN) mRNA than the control, and there were no significant differences for Runx2 and osteocalcin (OCN) mRNA levels compared with those cultured in microplates. In the presence of osteogenic inducers, Runx2 expression levels were significantly higher than those in control. OPN and OCN mRNA levels were downregulated slightly. Three-dimensional porous BCP scaffolds are able to stimulate the osteoblastic differentiation of hPDLCs in the presence and absence of osteogenic inducer and may be capable of supporting hPDLC-mediated bone formation.

Age-related decline in the matrix contents and functional properties of human periodontal ligament stem cell sheets

In this study, periodontal ligament (PDL) stem cells (PDLSCs) derived from different-aged donors were used to evaluate the effect of aging on cell sheet formation. The activity of PDLSCs was first determined based on their colony-forming ability, surface markers, proliferative/differentiative potentials, senescence-associated β-galactosidase (SA-βG) staining, and expression of pluripotency-associated transcription factors. The ability of these cells to form sheets, based on their extracellular matrix (ECM) contents and their functional properties necessary for osteogenic differentiation, was evaluated to predict the age-related changes in the regenerative capacity of the cell sheets in their further application. It was found that human PDLSCs could be isolated from the PDL tissue of different-aged subjects. However, the ability of the PDLSCs to proliferate and to undergo osteogenic differentiation and their expression of pluripotency-associated transcription factors displayed age-related decreases. In addition, these cells exhibited an age-related increase in SA-βG expression. Aged cells showed an impaired ability to form functional cell sheets, as determined by morphological observations and Ki-67 immunohistochemistry staining. Based on the production of ECM proteins, such as fibronectin, integrin β1, and collagen type I; alkaline phosphatase (ALP) activity; and the expression of osteogenic genes, such as ALP, Runt-related transcription factor 2, and osteocalcin, cell sheets formed by PDLSCs derived from older donors demonstrated a less potent osteogenic capacity compared to those formed by PDLSCs from younger donors. Our data suggest that the age-associated decline in the matrix contents and osteogenic properties of PDLSC sheets should be taken into account in cell sheet engineering research and clinical periodontal regenerative therapy.

Activation of the Canonical Wnt Signaling Pathway Induces Cementum Regeneration

Canonical Wnt signaling is important in tooth development but it is unclear whether it can induce cementogenesis and promote the regeneration of periodontal tissues lost because of disease. Therefore, the aim of this study is to investigate the influence of canonical Wnt signaling enhancers on human periodontal ligament cell (hPDLCs) cementogenic differentiation in vitro and cementum repair in a rat periodontal defect model. Canonical Wnt signaling was induced by (1) local injection of lithium chloride; (2) local injection of sclerostin antibody; and (3) local injection of a lentiviral construct overexpressing β-catenin. The results showed that the local activation of canonical Wnt signaling resulted in significant new cellular cementum deposition and the formation of well-organized periodontal ligament fibers, which was absent in the control group. In vitro experiments using hPDLCs showed that the Wnt signaling pathway activators significantly increased mineralization, alkaline phosphatase (ALP) activity, and gene and protein expression of the bone and cementum markers osteocalcin (OCN), osteopontin (OPN), cementum protein 1 (CEMP1), and cementum attachment protein (CAP). Our results show that the activation of the canonical Wnt signaling pathway can induce in vivo cementum regeneration and in vitro cementogenic differentiation of hPDLCs.

FGF-2 induces the proliferation of human periodontal ligament cells and modulates their osteoblastic phenotype by affecting Runx2 expression in the presence and absence of osteogenic inducers

The exact phenotype of human periodontal ligament cells (hPDLCs) remains a controversial area. Basic fibroblast growth factor (FGF-2) exhibits various functions and its effect on hPDLCs is also controversial. Therefore, the present study examined the effect of FGF-2 on the growth and osteoblastic phenotype of hPDLCs with or without osteogenic inducers (dexamethasone and β-glycerophosphate). FGF-2 was added to defined growth culture medium and osteogenic inductive culture medium. Cell proliferation, osteogenic differentiation and mineralization were measured. The selected differentiation markers, Runx2, collagen type I, α1 (Col1a1), osteocalcin (OCN) and epidermal growth factor receptor (EGFR), were investigated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Runx2 and OCN protein expression was measured by western blotting. FGF-2 significantly increased the proliferation of hPDLCs, but did not affect alkaline phosphatase activity. RT-qPCR analysis revealed enhanced mRNA expression of Runx2, OCN and EGFR, but suppressed Col1a1 gene expression in the absence of osteogenic inducers, whereas all these gene levels had no clear trend in their presence. The Runx2 protein expression was clearly increased, but the OCN protein level showed no evident trend. The mineralization assay demonstrated that FGF-2 inhibited mineralized matrix deposition with osteogenic inducers. These results suggested that FGF-2 induces the growth of immature hPDLCs, which is a competitive inhibitor of epithelial downgrowth, and suppresses their differentiation into mineralized tissue by affecting Runx2 expression. Therefore, this may lead to the acceleration of periodontal regeneration.

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.

A comparative study of the proliferation and osteogenic differentiation of human periodontal ligament cells cultured on β-TCP ceramics and demineralized bone matrix with or without osteogenic inducers in vitro

The repair of bone defects that result from periodontal diseases remains a clinical challenge for periodontal therapy. β-tricalcium phosphate (β-TCP) ceramics are biodegradable inorganic bone substitutes with inorganic components that are similar to those of bone. Demineralized bone matrix (DBM) is an acid-extracted organic matrix derived from bone sources that consists of the collagen and matrix proteins of bone. A few studies have documented the effects of DBM on the proliferation and osteogenic differentiation of human periodontal ligament cells (hPDLCs). The aim of the present study was to investigate the effects of inorganic and organic elements of bone on the proliferation and osteogenic differentiation of hPDLCs using three-dimensional porous β-TCP ceramics and DBM with or without osteogenic inducers. Primary hPDLCs were isolated from human periodontal ligaments. The proliferation of the hPDLCs on the scaffolds in the growth culture medium was examined using a Cell-Counting kit-8 (CCK-8) and scanning electron microscopy (SEM). Alkaline phosphatase (ALP) activity and the osteogenic differentiation of the hPDLCs cultured on the β-TCP ceramics and DBM were examined in both the growth culture medium and osteogenic culture medium. Specific osteogenic differentiation markers were examined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). SEM images revealed that the cells on the β-TCP were spindle-shaped and much more spread out compared with the cells on the DBM surfaces. There were no significant differences observed in cell proliferation between the β-TCP ceramics and the DBM scaffolds. Compared with the cells that were cultured on β-TCP ceramics, the ALP activity, as well as the Runx2 and osteocalcin (OCN) mRNA levels in the hPDLCs cultured on DBM were significantly enhanced both in the growth culture medium and the osteogenic culture medium. The organic elements of bone may exhibit greater osteogenic differentiation effects on hPDLCs than the inorganic elements.

Periodontal tissue regeneration by transplantation of rat adipose-derived stromal cells in combination with PLGA-based solid scaffolds

Regeneration of damaged periodontium is challenging due to its multi-tissue composition. Mesenchymalstem cell-based approaches using adipose-derived stromal cells (ASCs) may contribute to periodontal reconstruction, particularly when combined with the use of scaffolds to maintain a space for new tissue growth. The aim of this study was to assess the regenerative potential of ASCs derived from inbred or outbred rats in combination with novel solid scaffolds composed of PLGA (Poly D,L-lactic-co-glycolic acid) (PLGA-scaffolds). Cultured ASCs seeded onto PLGA scaffolds (ASCs/PLGA) or PLGA-scaffolds (PLGA) alone were transplanted into periodontal fenestration defects created in F344 or Sprague Dawley (SD) rats. Micro-CT analysis showed a significantly higher percentage of bone growth in the ASCs/PLGA groups compared with the PLGA-alone groups at five weeks after surgery. Similarly, histomorphometric analysis demonstrated thicker growth of periodontal ligament and cementum layers in the ASCs/PLGA-groups compared with the PLGA-alone groups. In addition, transplanted DiI-labeled ASCs were observed in the periodontal regenerative sites. The present investigation demonstrated the marked ability of ASCs in combination with PLGA scaffolds to repair periodontal defects.

Comparison of mesenchymal stem cells isolated from pulp and periodontal ligament

BACKGROUND

Cell-based therapy using mesenchymal stem cells (MSCs) seems promising to obtain regeneration of dental tissues. A comparison of tissue sources, including periodontal ligament (PDL) versus pulp (P), could provide critical information to select an appropriate MSC population for designing predictable regenerative therapies. The purpose of this study is to compare the proliferation and stemness and the MSC-specific and mineralized tissue-specific gene expression of P-MSCs and PDL-MSCs.

METHODS

MSCs were obtained from PDL and P tissue of premolars (n = 3) extracted for orthodontic reasons. MSC proliferation was evaluated using a real-time cell analyzer for 160 hours. Telomerase activity was evaluated by a telomeric repeat amplification protocol assay based on enzyme-linked immunosorbent assay. Total RNA was isolated from the MSCs on day 3. A polymerase chain reaction (PCR) array was used to compare the expression of MSC-specific genes. The expression of mineralized tissue-associated genes, including Type I collagen (COL I), runt-related transcription factor 2 (RunX2), bone sialoprotein (BSP), and osteocalcin (OCN) messenger RNA (mRNA), was evaluated using quantitative real-time PCR.

RESULTS

Higher proliferation potential and telomerase activity were observed in the P-MSCs compared to PDL-MSCs of premolar teeth. Fourteen of 84 genes related to MSCs were expressed differently in the PDL-MSCs versus the P-MSCs. The expressions of bone morphogenetic protein 2 (BMP2) and BMP6; sex-determining region Y-box 9 (SOX9); integrin, alpha 6 (ITGA6); melanoma cell adhesion molecule (MCAM); phosphatidylinositol glycan anchor biosynthesis, class S (PIGS); prominin 1 (PROM1); ribosomal protein L13A (RPL13A); and microphthalmia-associated transcription factor (MITF) were higher in the P-MSCs compared to the PDL-MSCs, and higher expression of matrix metalloproteinase 2 (MMP2), interleukin (IL)-6, insulin (INS), alanyl (membrane) aminopeptidase (ANPEP), and IL-10 were observed in the PDL-MSCs. However, there was no statistically significant difference in the expression of mineralized tissue-associated genes, including BSP and RunX2, between the P-MSCs and the PDL-MSCs. Higher expression of COL I and lower expression of OCN mRNA transcripts were noted in the PDL-MSCs compared to the P-MSCs.

CONCLUSIONS

The results of this study suggest that MSCs isolated from P and PDL tissues show different cellular behavior. To increase the predictability of MSC-based regenerative treatment, differences in dental tissue-derived MSCs and favorable aspects of cell sources should be further clarified.