Isolation and characterization of multipotent human periodontal ligament stem cells

Application of mesenchymal stem/stromal cells in periodontal regeneration: Opportunities and challenges

Guided tissue regeneration (GTR) has been widely used in the periodontal treatment of intrabony and furcation defects for nearly four decades. The treatment outcomes have shown effectiveness in reducing pocket depth, improving attachment gain and bone filling in periodontal tissue. Although applying GTR could reconstruct the periodontal tissue, the surgical indications are relatively narrow, and some complications and race ethic problems bring new challenges. Therefore, it is challenging to achieve a consensus concerning the clinical benefits of GTR. With the appearance of stem cell-based regenerative medicine, mesenchymal stem/stromal cells (MSCs) have been considered a promising cell resource for periodontal regeneration. In this review, we highlight preclinical and clinical periodontal regeneration using MSCs derived from distinct origins, including non-odontogenic and odontogenic tissues and induced pluripotent stem cells, and discuss the transplantation procedures, therapeutic mechanisms, and concerns to evaluate the effectiveness of MSCs.

Effects of adding graphene fibers to polymethyl methacrylate on biocompatibility and surface characterization

STATEMENT OF PROBLEM

Interim fixed prostheses are used provisionally to provide esthetics and maintain function until placement of the definitive prosthesis. Polymethyl methacrylate (PMMA) has been widely used as an interim material but has mechanical limitations that can be improved with the addition of nanomaterials such as graphene fibers (PMMA-G). However, studies on the biocompatibility of this material are lacking.

PURPOSE

The purpose of this in vitro study was to determine the biocompatibility and cytotoxic effects of PMMA compared with PMMA-G in periodontal ligament stem cells (PDLSCs) by measuring the viability and cell apoptosis of those cells subjected to different concentrations of both compounds by elution, as well as the surface characterization of these materials.

MATERIAL AND METHODS

Sterile Ø20×15-mm specimens of PMMA and PMMA-G were covered with Dulbecco modified Eagle medium for 24 hours to be the subsequent eluent. PDLSCs were seeded in 6 plates of 96 wells at dilutions 1/1, 1/2, 1/4, and 1/8 for each material. Three plates for the cell viability assay with MTT and 3 plates for the cell apoptosis assay with Hoechst 33342 staining were used in turn to subdivide the measurements at 24, 48, and 72 hours. The Kruskal-Wallis test was used to compare the data obtained in the different dilutions at different times and the Mann-Whitney test to compare both materials. Topography and wetting were analyzed for surface characterization. The Student t test of paired measurements was used to compare the different surfaces for each parameter (α=.05 for all tests).

RESULTS

In both the cell viability assay (MTT) and the cell apoptosis assay, the test did not identify statistically significant differences in PMMA and PMMA-G with respect to the control group in the different dilutions at different times (P>.05). When comparing both materials, no statistically significant differences (P=.268) were found in either trial. PMMA-G had lower roughness and kurtosis and higher wetting than PMMA.

CONCLUSIONS

Both PMMA and PMMA-G were found to be biocompatible materials with no significant differences between them after cell viability and apoptosis testing. PMMA-G had higher wettability and lower roughness than PMMA.

Small extracellular vesicles derived from lipopolysaccharide-preconditioned dental follicle cells inhibit cell apoptosis and alveolar bone loss in periodontitis

OBJECTIVE

This study aimed to explore the effects of small extracellular vesicles derived from lipopolysaccharide-preconditioned dental follicle cells (L-D-sEV) on periodontal ligament cells from periodontitis affected teeth (p-PDLCs) in vitro and experimental periodontitis in mice.

DESIGN

In vitro, the biological function of p-PDLCs and the underlying molecular mechanism were investigated by flow cytometry, Western blot, and quantitative real-time PCR (qRT-PCR) analysis. Eighteen-eight-week-old male C57BL/6 mice were randomly divided into three groups: control (Con), periodontitis (Peri), and L-D-sEV groups. Mice periodontitis model was induced by placing the 5-0 silk thread (around the maxillary second molar) and P.gingivalis (1 ×107 CFUs per mouse). In vivo, the alveolar bone loss, osteoclast activity, and macrophage polarization were measured by micro-computed tomography and histological analysis.

RESULTS

In vitro, the RANKL/OPG ratio and phosphorylation of JNK and P38 protein levels of p-PDLCs were significantly decreased after L-D-sEV administration. Besides, flow cytometry and qRT-PCR analysis showed that L-D-sEV reduced apoptosis of p-PDLCs, down-regulated apoptosis-related genes Caspase-3 and BCL-2-Associated X expression, and up-regulated B-cell lymphoma-2 gene levels. In vivo, L-D-sEV administration significantly reduced alveolar bone loss, inhibited osteoclast activity, and induced M2 polarization. The histological analysis showed that iNOS/CD206, RANKL/OPG, p-JNK/JNK, and p-P38/P38 ratios were significantly lower in the L-D-sEV group than in the Peri group.

CONCLUSIONS

L-D-sEV administration alleviated alveolar bone loss by mediating RANKL/OPG-related osteoclast activity and M2 macrophage polarization, alleviating p-PDLCs apoptosis and proliferation via the JNK and P38 pathways.

Gingiva Mesenchymal Stem Cells Normoxic or Hypoxic Preconditioned Application Under Orthodontic Mechanical Force on Osterix, Osteopontin, and ALP Expression

OBJECTIVES

 The aim of this article was to investigate Osterix, ALP, and osteopontin expression in the compression and tension sides of alveolar bone after the application of normoxic/hypoxic-preconditioned GMSCs in rabbits (Oryctolagus cuniculus) induced with OMF.

MATERIALS AND METHODS

 Forty-eight healthy, young male rabbits were divided into four groups: [-] OMF; [+] OMF; OMF with GMSCs normoxic-preconditioned; and OMF and GMSCs hypoxic-preconditioned. The central incisor and left mandibular molar in the experimental animals were moved, the mandibular first molar was moved mesially using nickel titanium (NiTi) and stainless steel ligature wire connected to a 50 g/mm2 light force closed coil spring. Allogeneic application of normoxic or hypoxic-preconditioned GMSCs was used in as many as 106 cells in a 20 µL phosphate buffered saline single dose and injected into experimental animals' gingiva after 1 day of OTM. On days 7, 14, and 28, all experimental animals were euthanized. Osterix, ALP, and osteopontin expressions were examined by immunohistochemistry.

RESULTS

 Osterix, ALP, and osteopontin expressions were significantly different after allogeneic application of hypoxic-preconditioned GMSCs than normoxic-preconditioned GMSCs in the tension and compression of the alveolar bone side during OMF (p < 0.05).

CONCLUSION

 Osterix, ALP, and osteopontin expressions were significantly more enhanced post-transplantation of GMSCs with hypoxic-preconditioning than after transplantation of normoxic-preconditioned GMSCs in rabbits (O. cuniculus) induced with OMF.

Effect of Fibrillin-2 on Differentiation into Periodontal Ligament Stem Cell-Like Cells Derived from Human-Induced Pluripotent Stem Cells

Periodontal tissue regeneration is important for preserving teeth. Periodontal ligament stem cells (PDLSCs) are useful in periodontal tissue regeneration; however, tooth extraction is required to obtain these cells. Therefore, we focused on induced pluripotent stem (iPS) cells and established a method to obtain PDLSC-like cells from iPS cells. Specifically, we first differentiated iPS cells into neural crest-like cells (iNCs). Next, we obtained PDLSC-like cells (iPDLSCs) by culturing iNCs on extracellular matrix (ECM) derived from human primary periodontal ligament cells (HPDLCs). This differentiation method suggested that ECM derived from HPDLCs is important for iPDLSC differentiation. Thus, we aimed to identify the PDLSC-inducing factor present in HPDLC-derived ECM in this study. We first performed comprehensive analyses of HPDLC genes and identified fibrillin-2 (FBN2), an ECM-related factor. Furthermore, to clarify the effect of FBN2 on iPDLSC differentiation, we cultured iNCs using ECM derived from HPDLCs with FBN2 knocked down. As a result, expression of PDL-related markers was reduced in iNCs cultured on ECM derived from HPDLCs transfected with FBN2 siRNA (iNC-siFBN2) compared with iPDLSCs. Furthermore, the expression of CD105 (a mesenchymal stem cell marker), proliferation ability, and multipotency of iNC-siFBN2 were lower compared with iPDLSCs. Next, we cultured iNCs on FBN2 recombinant protein; however, expression of PDL-related markers did not increase compared with iPDLSC. The present results suggest the critical involvement of FBN2 in inducing iPDLSCs from iNCs when in fact it does not promote iPDLSC differantiation. Therefore, we need to elucidate the entire HPDLC-ECMs, responsible for iPDLSCs induction.

Trends of regenerative tissue engineering for oral and maxillofacial reconstruction in veterinary medicine

Oral and maxillofacial (OMF) defects are not limited to humans and are often encountered in other species. Reconstructing significant tissue defects requires an excellent strategy for efficient and cost-effective treatment. In this regard, tissue engineering comprising stem cells, scaffolds, and signaling molecules is emerging as an innovative approach to treating OMF defects in veterinary patients. This review presents a comprehensive overview of OMF defects and tissue engineering principles to establish proper treatment and achieve both hard and soft tissue regeneration in veterinary practice. Moreover, bench-to-bedside future opportunities and challenges of tissue engineering usage are also addressed in this literature review.

Infrared diode laser enhances human periodontal ligament stem cells behaviour on titanium dental implants

Low level laser treatment (LLLT) is known for its photobiostimulatory and photobiomodulatory characteristics, which stimulate cell proliferation, increase cellular metabolism, and improve cellular regeneration. The objective of the present research was to assess the possible influence of infrared diode laser irradiation on the behaviour, attachment, and osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) seeded on different types of dental implants. Two distinct types of implants, one subjected to laser surface treatment and the other treated with acid etching, were longitudinally divided into two halves and submerged in six wells culture plates. Both implants were subjected to infrared diode laser treatment, and subsequently, the morphology and attachment of cells were examined using scanning electron microscopy (SEM) after 14 and 21 days. The behaviour of (hPDLSCs) towards two types of implants, when exposed to osteogenic medium and low-level laser therapy (LLLT), was assessed using quantitative real-time polymerase chain reaction to measure the expression of stemness markers and osteogenic markers. The scanning electron microscopy (SEM) demonstrated that the application of infrared diode laser irradiation substantially improved the attachment of cells to both types of implants. The stemness gene markers were significantly down regulated in cells seeded on both surfaces when challenged with osteogenic media in relation to control. At 14 days, early osteogenic markers, were upregulated, while late osteogenic markers, were downregulated in both challenged groups. At the 21-day mark, hPDLSCs seeded on an acid-etched implant exhibited increased expression of all osteogenic markers in response to stimulation with osteogenic media and infra-red diode laser, in contrast to hPDLSCs seeded on a laser surface treated implant under the same conditions. Finally, the findings of our research revealed that when subjected to infrared diode laser, human periodontal ligament stem cells cultured on both types of implants demonstrated improved cellular attachment and differentiation. This suggested that infrared diode laser enhanced the activity of the cells surrounding the implants. Hence, the use of infrared diode laser could be pivotal in improving and expediting the clinical osseointegration process around dental implants.

Exosomal circ_0000722 derived from periodontal ligament stem cells undergoing osteogenic differentiation promotes osteoclastogenesis

Periodontal ligament stem cells (PDLSCs), which are considered promising stem cells for regeneration of periodontal bony tissue, can also manipulate alveolar bone remodeling by exosomes. In this study, we investigated interactions between PDLSCs under osteogenic differentiation and osteoclast precursors. The results showed that conditioned medium from PDLSCs under 5d osteogenic induction promoted osteoclastogenesis of RAW264.7 cells. The exosomes extracted from those conditioned media showed similar effects on osteoclastogenesis. Furthermore, exosomes from PDLSCs under 5d of osteogenic induction showed significantly high expression of circ_0000722, compared with exosomes from PDLSCs before osteogenic induction. Downregulation of circ_0000722 significantly attenuated the effect of PDLSC-derived exosomes on the osteoclastogenesis of RAW264.7 cells. Our findings suggested that exosomal circ_0000722 derived from periodontal ligament stem cells undergoing osteogenic differentiation might promote osteoclastogenesis by upregulating TRAF6 expression and activating downstream NF-κB and AKT signaling pathways.

Photo biomodulation of dental derived stem cells to ameliorate regenerative capacity: In vitro study

Background

Dental regeneration benefits from improving the features of dental derived stem cells. Gallium-aluminum-arsenide laser had a significant role in modification of cell behavior in different cell lines and culture conditions. Hence, exploring its mechanism and effect on dental derived stem cells would benefit prospective regenerative dental therapies.

Objectives

To assess the impact of photo biomodulation by Low-Level-Laser on isolated Dental Pulp derived Stem Cells and Periodontal Ligament derived Stem Cells regarding their proliferation and osteogenic differentiation.

Methods

Isolated DPSCs and PDLSCs from impacted third molars were subjected to Gallium-aluminum-arsenide laser for 12 sec and 3.6 J/cm2. The proliferative capacity was evaluated via 3-(4,5-dimethylthiazol-2-yl),2,5-diphenyltetrazolium bromide (MTT) Assay and Trypan blue stain. Cell osteogenic differentiation potentials were assessed by alkaline phosphatase assay and alizarin red stain, polymerase chain reaction was performed to quantify Nuclear factor Kappa gene expression.

Results

DPSCs subjected to laser bio-stimulation showed the best results regarding cell viability (MTT) and osteogenic differentiation (ALP assay), and calcium deposition at 3 intervals (3, 7, 14 days), meanwhile, PDLSCs subjected to laser bio-stimulation showed better result than control but less than DPSCs. While NF-KB gene expression was proven to be approximately comparable for both groups. Generally, the Photo-bio modulated groups showed better results than their control groups.

Conclusion

Low-level laser bio-stimulation (LLL) therapy improves DPSC and PDLSC osteogenic differentiation and proliferation via the activation of the NF-KB pathway. Also, the DPSCs outperformed PDLSCs in terms of performance.

Clinical significance

These results can be beneficial information and a reference database for more research in tissue engineering, dental therapy, and regeneration.

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.

Fundamentals and Translational Applications of Stem Cells and Biomaterials in Dental, Oral and Craniofacial Regenerative Medicine

Regenerative dental medicine continuously expands to improve treatments for prevalent clinical problems in dental and oral medicine. Stem cell based translational opportunities include regenerative therapies for tooth restoration, root canal therapy, and inflammatory processes (e.g., periodontitis). The potential of regenerative approaches relies on the biological properties of dental stem cells. These and other multipotent somatic mesenchymal stem cell (MSC) types can in principle be applied as either autologous or allogeneic sources in dental procedures. Dental stem cells have distinct developmental origins and biological markers that determine their translational utility. Dental regenerative medicine is supported by mechanistic knowledge of the molecular pathways that regulate dental stem cell growth and differentiation. Cell fate determination and lineage progression of dental stem cells is regulated by multiple cell signaling pathways (e.g., WNTs, BMPs) and epigenetic mechanisms, including DNA modifications, histone modifications, and non-coding RNAs (e.g., miRNAs and lncRNAs). This review also considers a broad range of novel approaches in which stem cells are applied in combination with biopolymers, ceramics, and composite materials, as well as small molecules (agonistic or anti-agonistic ligands) and natural compounds. Materials that mimic the microenvironment of the stem cell niche are also presented. Promising concepts in bone and dental tissue engineering continue to drive innovation in dental and non-dental restorative procedures.

Proanthocyanidin enhances the endogenous regeneration of alveolar bone by elevating the autophagy of PDLSCs

OBJECTIVE

This study aimed to investigate the effect of proanthocyanidin (PA) on osteogenesis mediated by periodontal ligament stem cells (PDLSCs) and endogenous alveolar bone regeneration.

BACKGROUND

Leveraging the osteogenic potential of resident stem cells is a promising strategy for alveolar bone regeneration. PA has been reported to be effective in osteogenesis. However, the effect and mechanism of PA on the osteogenic differentiation of PDLSCs remain elusive.

METHODS

Human PDLSCs were treated with various doses of PA to assess the cell proliferation using Cell Counting Kit-8. The osteogenic differentiation ability was detected by qRT-PCR analysis, western blot analysis, Alizarin red S staining, and Alkaline Phosphatase staining. The level of autophagy was evaluated by confocal laser scanning microscopy, transmission electron microscopy, and western blot analysis. RNA sequencing was utilized to screen the potential signaling pathway. The alveolar bone defect model of rats was created to observe endogenous bone regeneration.

RESULTS

PA activated intracellular autophagy in PDLSCs, resulting in enhanced osteogenic differentiation. Moreover, this effect could be abolished by the autophagy inhibitor 3-Methyladenine. Mechanistically, the PI3K/Akt/mTOR pathway was negatively correlated with PA-mediated autophagy activation. Lastly, PA promoted the alveolar bone regeneration in vivo, and this effect was reversed when the autophagy process was blocked.

CONCLUSION

PA may activate autophagy by inhibiting PI3K/Akt/mTOR signaling pathway to promote the osteogenesis of PDLSCs and enhance endogenous alveolar bone regeneration.

A comparison of osteogenic effect of newly manufactured calcium silicate-based sealers in vitro

This study aimed to assess the effect of different calcium silicate-based root canal sealers (CSRS) on osteogenic effect in human periodontal ligament cells (hPDLCs). hPDLCs were cultured in a medium containing extract of 5 types of CSRS. The specimens were assessed by the cell cytotoxicity test, alkaline phosphatase staining, alizarin red S staining, quantitative real-time PCR, Western blot analysis, and enzyme-linked immunosorbent assay. The diluted concentrations of extracted solutions had no significant effect on the viability of hPDLCs. There was a statistically significant difference in the mRNA expression level of bone sialoprotein (BSP), osteocalcin (OCN), and runt-related transcription factor 2 (RUNX2) among some groups. The protein expressions of BSP, OCN, and RUNX2 were significantly higher in some groups compared to the control group. The CSRS did not interfere with the osteogenic differentiation of hPDLCs, compared to the control group. CSRS are shown to have biocompatibility and osteogenic differentiation effect on hPDLCs.

Ageing and Inflammation: What Happens in Periodontium?

Periodontitis is a chronic inflammatory disease with a high incidence and severity in the elderly population, making it a significant public health concern. Ageing is a primary risk factor for the development of periodontitis, exacerbating alveolar bone loss and leading to tooth loss in the geriatric population. Despite extensive research, the precise molecular mechanisms underlying the relationship between ageing and periodontitis remain elusive. Understanding the intricate mechanisms that connect ageing and inflammation may help reveal new therapeutic targets and provide valuable options to tackle the challenges encountered by the rapidly expanding global ageing population. In this review, we highlight the latest scientific breakthroughs in the pathways by which inflammaging mediates the decline in periodontal function and triggers the onset of periodontitis. We also provide a comprehensive overview of the latest findings and discuss potential avenues for future research in this critical area of investigation.

MicroRNAs Function in Dental Stem Cells as a Promising Biomarker and Therapeutic Target for Dental Diseases

Undifferentiated, highly proliferative, clonogenic, and self-renewing dental stem cells have paved the way for novel approaches to mending cleft palates, rebuilding lost jawbone and periodontal tissue, and, most significantly, recreating lost teeth. New treatment techniques may be guided by a better understanding of these cells and their potential in terms of the specificity of the regenerative response. MicroRNAs have been recognized as an essential component in stem cell biology due to their role as epigenetic regulators of the processes that determine stem cell destiny. MicroRNAs have been proven to be crucial in a wide variety of molecular and biological processes, including apoptosis, cell proliferation, migration, and necrocytosis. MicroRNAs have been recognized to control protein translation, messenger RNA stability, and transcription and have been reported to play essential roles in dental stem cell biology, including the differentiation of dental stem cells, the immunological response, apoptosis, and the inflammation of the dental pulp. Because microRNAs increase dental stem cell differentiation, they may be used in regenerative medicine to either preserve the stem cell phenotype or to aid in the development of tooth tissue. The development of novel biomarkers and therapies for dental illnesses relies heavily on progress made in our knowledge of the roles played by microRNAs in regulating dental stem cells. In this article, we discuss how dental stem cells and their associated microRNAs may be used to cure dental illness.

The Role of XBP1 in bone metabolism

Bone is a dynamic organ that, once formed, undergoes a constant remodeling process that includes bone resorption and synthesis. Osteoclasts and osteoblasts are primarily responsible for controlling this process. X-box binding protein 1 (XBP1), a transcription factor, affects the metabolism of bones in various ways. In recent years, numerous studies have revealed that XBP1 plays a vital role in bone metabolism, including osteoclast and osteoblast development, as well as in regulating immune cell differentiation that affects the immune microenvironment of bone remodeling. In this review, we highlight the regulatory mechanisms of XBP1 on osteoclasts and osteoblasts, how XBP1 affects the immune microenvironment of bone remodeling by influencing the differentiation of immune cells, and predict the possible future research directions of XBP1 to provide new insights for the treatment of bone-related metabolic diseases.

Ligaplants: Uprising Regimen in the Glebe of Implant Dentistry

A dental implant is an alloplastic framework inserted into the bone, either straight through the alveolar bone or beneath the mucosa or periosteum, to support and hold a permanent or removable dental prosthesis. Osseointegration is a striking phenomenon in which bone directly opposes the implant surface without any interposing collagen or fibroblastic matrix. Although titanium metallic implants were the subject of "osseointegration" at first, it is now used to refer to any biomaterial that can osseointegrate. The science of tissue engineering allows for regenerating complete biological components outside the body for possible replacement treatment or therapy. It uses cells, organic or synthetic scaffold materials, and bioactive molecules. The combination of periodontal ligament (PDL) cells with implant biomaterial is known as Ligaplants. When placed in regions with significant periodontal bone defects, ligaplants can promote the development of new bone. PDL implants, inserted into the missing teeth extraction socket, facilitate surgery. To protect the PDL cell cushion, ligaplants are fitted initially loosely. However, they firmly integrate without interlocking or making direct contact with the bones. Osseointegrated implants affixed directly to the alveolar bone encircling them cannot serve the same purpose as healthy teeth because natural periodontal tissue deteriorates over time. To create a biological connection capable of performing specific physiological tasks, a tissue-engineered PDL must be constructed in conjunction with a dental implant that is well thought out.

Adult Mesenchymal Stem Cells from Oral Cavity and Surrounding Areas: Types and Biomedical Applications

Adult mesenchymal stem cells are those obtained from the conformation of dental structures (DMSC), such as deciduous and permanent teeth and other surrounding tissues. Background: The self-renewal and differentiation capacities of these adult stem cells allow for great clinical potential. Because DMSC are cells of ectomesenchymal origin, they reveal a high capacity for complete regeneration of dental pulp, periodontal tissue, and other biomedical applications; their differentiation into other types of cells promotes repair in muscle tissue, cardiac, pancreatic, nervous, bone, cartilage, skin, and corneal tissues, among others, with a high predictability of success. Therefore, stem and progenitor cells, with their exosomes of dental origin and surrounding areas in the oral cavity due to their plasticity, are considered a fundamental pillar in medicine and regenerative dentistry. Tissue engineering (MSCs, scaffolds, and bioactive molecules) sustains and induces its multipotent and immunomodulatory effects. It is of vital importance to guarantee the safety and efficacy of the procedures designed for patients, and for this purpose, more clinical trials are needed to increase the efficacy of several pathologies. Conclusion: From a bioethical and transcendental anthropological point of view, the human person as a unique being facilitates better clinical and personalized therapy, given the higher prevalence of dental and chronic systemic diseases.

Comparison of Biological Properties and Clinical Application of Mesenchymal Stem Cells from the Mesoderm and Ectoderm

Since the discovery of mesenchymal stem cells (MSCs) in the 1970s, they have been widely used in the treatment of a variety of diseases because of their wide sources, strong differentiation potential, rapid expansion in vitro, low immunogenicity, and so on. At present, most of the related research is on mesoderm-derived MSCs (M-MSCs) such as bone marrow MSCs and adipose-derived MSCs. As a type of MSC, ectoderm-derived MSCs (E-MSCs) have a stronger potential for self-renewal, multidirectional differentiation, and immunomodulation and have more advantages than M-MSCs in some specific conditions. This paper analyzes the relevant research development of E-MSCs compared with that of M-MSCs; summarizes the extraction, discrimination and culture, biological characteristics, and clinical application of E-MSCs; and discusses the application prospects of E-MSCs. This summary provides a theoretical basis for the better application of MSCs from both ectoderm and mesoderm in the future.

In vitro investigation of canine periodontal ligament-derived mesenchymal stem cells: A possibility of promising tool for periodontal regeneration

Objectives

Recent investigations indicate that canine periodontal ligament-derived stem cells (cPDLSCs) may reveal a reliable strategy for repair of periodontal tissues via cell-based tissue engineering approaches. Due to limited research, this study aimed to demonstrate the phenotypic characterization of cPDLSc in comparison with canine bone marrow-derived mesenchymal stem cells (cBMSCs) in vitro.

Methods

Mesenchymal stem cells (MSCs) were obtained from PDL and BM of five male adult Mongrel dogs. In vitro isolation and expansion as well as biologic characterization including colony unit formation (CFU), osteogenic and adipogenic differentiation, flow cytometric analysis of CD34 and CD44, and RT-PCR of alkaline phosphatase (ALP), osteocalcin (OCN), periostin (POSTN) and S100A4 were performed. Furthermore, electron microscopy analysis was done to complement the comparative research.

Results

CFU assay revealed that colonies of cPDLSCs presented 70% confluency with a more finite lifespan than BM-MSCs, showing a significant increase in cPDLSCs. Both types of MSCs showed osteogenic and adipogenic phenotypic characterized with clusters of mineralized depositions and lipid vacuoles, respectively. Both types of MSCs expressed CD44 with limited expression of CD34. RT-PCR of cPDLSCs revealed that expression of ALP, POSTN, OCN and S100A4 genes were significantly higher than those of BMSCs. In addition, comparison of SEM and revealed that cPDLSCs expressed more extracellular collagen fibers.

Conclusions

The current study indicated that cPDLSCs show potency as a novel cellular therapy for periodontal regeneration a large animal model.

Periodontal ligament cells from patients with treated stable periodontitis: Characterization and osteogenic differentiation potential

BACKGROUND AND OBJECTIVE

Periodontal ligament progenitor cells (PDL cells) isolated from patients with inflammatory periodontitis have impaired regenerative capacity, but it is unknown whether this capacity can be recovered upon treatment and stabilization of the periodontal condition. The study aimed to investigate the expression of surface markers and the proliferation and osteogenic potential of PDL cells isolated from patients with treated stable periodontitis (S-PDL cells), periodontally healthy individuals (H-PDL cells), and patients with inflammatory periodontitis (I-PDL cells).

METHODS

H-PDL, I-PDL, and S-PDL cells were isolated from the extracted teeth of individuals who (1) were periodontally healthy, (2) had inflammatory periodontitis, and (3) had treated stable periodontitis, respectively. The expression levels of surface markers and the proliferative and osteogenic capacities of the PDL cells were assessed.

RESULTS

PDL cells derived from all three sources exhibited mesenchymal stem cell (MSC) characteristics. They were positive for MSC-related markers and negative for a hematopoiesis-related marker. However, S-PDL cells had higher proliferation rates, higher expression levels of osteogenic markers, higher alkaline phosphatase activity, and more calcium nodules than I-PDL cells. But all of these parameters remained lower in S-PDL cells than in H-PDL cells.

CONCLUSIONS

S-PDL cells proliferated faster and had greater osteogenic potential than I-PDL cells, although these values remained lower than those in H-PDL cells.

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.

Clinical and Radiographic Evaluation of Combined Acemannan and Periodontal Surgery Induced-Periodontal Regeneration: 5-Year Follow-up Case Report

Background and Objective:

Acemannan, a polysaccharide extracted from aloe vera gel, accelerates oral wound healing, reparative dentin formation, and bone formation in extraction sockets. In this report, we evaluated the efficacy of combined acemannan and periodontal surgery on periodontal regeneration in severe periodontitis cases requiring periodontal surgery.

Case Presentation and Discussion:

Three chronic periodontitis patients with probing pocket depths of at least 6 mm and two- or three-walled vertical bone defects after initial periodontal therapy were included. The patients underwent minimally invasive periodontal surgery with acemannan sponges placed in the defect. Maintenance recall was scheduled every 6 months for 5 years. Clinical and radiographic evaluations were performed to assess the effects of the combined acemannan and periodontal surgery on periodontal regeneration. The patients demonstrated improved clinical parameters and increased radiographic bone fill at the 5-year follow-ups. The percentage bone fill in the three-walled defect, combined two- and three-walled defect, and two-walled defect cases were 70%, 60%, and 20%, respectively. The underlying mechanism of action of acemannan in periodontal regeneration was also discussed.

Conclusion:

Acemannan sponges can be used as an adjunct to periodontal surgery for periodontal regeneration.

A Novel Perspective on Tissue Engineering Potentials of Periodontal Ligament Stem Cells

It is challenging to completely and predictably regenerate the missing periodontal tissues caused by the trauma or disease. To regenerate the periodontium, there is a need to consider several aspects that co-occur with periodontal development. This study provides an overview of the most up-to-date investigations on the characteristics and immunomodulatory features of Periodontal Ligament Stem Cells (PDLSCs) and the recent interventions performed using these cells, focusing on cell survival, proliferation, and differentiation. Keeping in mind the relationship between age and potency of PDLSCs, this work also demonstrates the necessity of establishing dental-derived stem cell banks for tissue regeneration applications. The data were collected from Pubmed and Google Scholar databases with the keywords of periodontal ligament stem cells, tissue engineering, characteristics, and stem cell therapy. The results showed the presence of wide-ranging research reports supporting the usability of PDLSCs for periodontal reconstruction. However, a better understanding of self-restoration for adequate regulation of adult stem cell growth is needed for various applied purposes.

Plumping up a Cushion of Human Biowaste in Regenerative Medicine: Novel Insights into a State-of-the-Art Reserve Arsenal

Major breakthroughs and disruptive methods in disease treatment today owe their thanks to our inch by inch developing conception of the infinitive aspects of medicine since the very beginning, among which, the role of the regenerative medicine can on no account be denied, a branch of medicine dedicated to either repairing or replacing the injured or diseased cells, organs, and tissues. A novel means to accomplish such a quest is what is being called "medical biowaste", a large assortment of biological samples produced during a surgery session or as a result of physiological conditions and biological activities. The current paper accentuating several of a number of promising sources of biowaste together with their plausible applications in routine clinical practices and the confronting challenges aims at inspiring research on the existing gap between clinical and basic science to further extend our knowledge and understanding concerning the potential applications of medical biowaste.

A Compilation of Study Models for Dental Pulp Regeneration

Efforts to heal damaged pulp tissue through tissue engineering have produced positive results in pilot trials. However, the differentiation between real regeneration and mere repair is not possible through clinical measures. Therefore, preclinical study models are still of great importance, both to gain insights into treatment outcomes on tissue and cell levels and to develop further concepts for dental pulp regeneration. This review aims at compiling information about different in vitro and in vivo ectopic, semiorthotopic, and orthotopic models. In this context, the differences between monolayer and three-dimensional cell cultures are discussed, a semiorthotopic transplantation model is introduced as an in vivo model for dental pulp regeneration, and finally, different animal models used for in vivo orthotopic investigations are presented.

Impact of Oral Mesenchymal Stem Cells Applications as a Promising Therapeutic Target in the Therapy of Periodontal Disease

Periodontal disease is a chronic inflammatory condition affecting about 20–50% of people, worldwide, and manifesting clinically through the detection of gingival inflammation, clinical attachment loss, radiographically assessed resorption of alveolar bone, gingival bleeding upon probing, teeth mobility and their potential loss at advanced stages. It is characterized by a multifactorial etiology, including an imbalance of the oral microbiota, mechanical stress and systemic diseases such as diabetes mellitus. The current standard treatments for periodontitis include eliminating the microbial pathogens and applying biomaterials to treat the bone defects. However, periodontal tissue regeneration via a process consistent with the natural tissue formation process has not yet been achieved. Developmental biology studies state that periodontal tissue is composed of neural crest-derived ectomesenchyme. The aim of this review is to discuss the clinical utility of stem cells in periodontal regeneration by reviewing the relevant literature that assesses the periodontal-regenerative potential of stem cells.

Osteogenesis in human periodontal ligament stem cell sheets is enhanced by the protease-activated receptor 1 (PAR1) in vivo

Human periodontal ligament stem cells (PDLSCs) have been studied as a promising strategy in regenerative approaches. The protease-activated receptor 1 (PAR₁) plays a key role in osteogenesis and has been shown to induce osteogenesis and increase bone formation in PDLSCs. However, little is known about its effects when activated in PDLSCs as a cell sheet construct and how it would impact bone formation as a graft in vivo. Here, PDLSCs were obtained from 3 patients. Groups were divided into control, osteogenic medium and osteogenic medium + PAR₁ activation by TFLLR-NH2 peptide. Cell phenotype was determined by flow cytometry and immunofluorescence. Calcium deposition was quantified by Alizarin Red Staining. Cell sheet microstructure was analyzed through light, scanning electron microscopy and histology and transplanted to Balb/c nude mice. Immunohistochemistry for bone sialoprotein (BSP), integrin β1 and collagen type 1 and histological stains (H&E, Van Giesson, Masson’s Trichrome and Von Kossa) were performed on the ex-vivo mineralized tissue after 60 days of implantation in vivo. Ectopic bone formation was evaluated through micro-CT. PAR₁ activation increased calcium deposition in vitro as well as BSP, collagen type 1 and integrin β1 protein expression and higher ectopic bone formation (micro-CT) in vivo.

Biomimetic Tubular Matrix Induces Periodontal Ligament Principal Fiber Formation and Inhibits Osteogenic Differentiation of Periodontal Ligament Stem Cells

Periodontal ligament (PDL) is assembled from highly organized collagen fiber bundles (PDL principal fibers) that are crucial in supporting teeth and buffering mechanical force. Therefore, regeneration of PDL needs to reconstruct these well-ordered fiber bundles to restore PDL functions. However, the formation of PDL principal fibers has long been a challenge due to the absence of an effective three-dimensional (3D) matrix to guide the growth of periodontal ligament stem cells (PDLSCs) and to inhibit the osteogenic differentiation of PDLSCs during the PDL principal fibers deposition. In this work, we designed and fabricated a bio-inspired tubular 3D matrix to guide the migration and growth of human PDLSCs and form well-aligned PDL principal fibers. As a biomimetic 3D template, the tubular matrix controlled PDLSCs migration inside the tubules and aligned the cells to the designated direction. Inside the tubular matrix, the PDLSCs expressed PDL markers and formed oriented fiber bundles with the same size and density as those of natural PDL principal fibers. Furthermore, the tubular matrix downregulated the osteogenic differentiation of PDLSCs. A mechanism study revealed that the Yap1/Twist1 signaling pathway was involved in the inhibition of PDLSCs osteogenesis within the tubular matrix. This work provides an effective approach to induce PDLSCs to form principal fibers and gives insight into the underlying mechanism of inhibiting the osteogenic differentiation of PDLSCs in biomimetic tubular matrices.

Cytocompatibility and bioactive potential of AH Plus Bioceramic Sealer: an in vitro study

Aim

To assess the cytocompatibility and bioactive potential of the new calcium silicate cement‐based sealer AH Plus Bioceramic Sealer (AHPbcs) on human periodontal ligament stem cells (hPDLSCs) compared with the epoxy resin‐based sealer AH Plus (AHP) and the calcium silicate cement‐based sealer Endosequence BC Sealer (ESbcs).

Methodology

Standardized sample discs and 1:1, 1:2 and 1:4 eluates of the tested materials were prepared. The following assays were performed: surface element distribution via SEM–EDX, cell attachment and morphology via SEM, cell viability via a MTT assay, cell migration/proliferation via a wound‐healing assay, osteo/cemento/odontogenic marker expression via RT‐qPCR and cell mineralized nodule formation via Alizarin Red S staining. HPDLSCs were isolated from extracted third molars. Comparisons were made with hPDLSCs cultured in unconditioned (negative control) or osteogenic (positive control) culture media. Statistical significance was established at p < .05.

Results

A higher peak of Ca²+ was detected from ESbcs compared with AHPbcs and AHP in SEM–EDX. Both AHPbcs and ESbcs showed significantly positive results in the cytocompatibility assays (cell viability, migration/proliferation, attachment and morphology) compared with a negative control group, whilst AHP showed significant negative results. Both AHPbcs and ESbcs exhibited an upregulation of at least one osteo/odonto/cementogenic marker compared with the negative and positive control groups. Both ESbcs and AHPbcs showed a significantly higher calcified nodule formation than the negative and positive control groups, indicative of their biomineralization potential and were also significantly higher than AHP group.

Conclusion

AH Plus Bioceramic Sealer exhibited a significantly higher cytocompatibility and bioactive potential than AH Plus and a similar cytocompatibility to that of Endosequence BC Sealer. Endosequence BC Sealer exhibited a significantly higher mineralization potential than the other tested sealers. The results from this in vitro study act as supporting evidence for the use of AH Plus Bioceramic Sealer in root canal treatment.

Osteogenic growth peptide enhances osteogenic differentiation of human periodontal ligament stem cells

Bone tissue engineering consists of three major components namely cells, scaffolds, and signaling molecules to improve bone regeneration. These integrated principles can be applied in patients suffered from bone resorption diseases, such as osteoporosis and periodontitis. Osteogenic growth peptide (OGP) is a fourteen-amino acid sequence peptide that has the potential to regenerate bone tissues. This study aimed to disseminate the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) with OGP treatment. OGP was elaborated for proliferation, cytotoxicity, osteogenic differentiation effects, and the involvement of osteogenic related signaling pathways in vitro. This study found that OGP at lower concentration shows better effects on cytotoxicity and proliferation. Moreover, OGP at concentration 0.01 nM had the most potential to differentiate hPDLSCs toward osteogenic lineage comparing with higher concentrations of OGP. The phenomenon was mainly involving transforming growth factor-beta (TGF-β), bone morphogenetic protein (BMP), Hedgehog, and Wingless-related (Wnt) pathways. Further, SB-431542 treatment demonstrated the partial involvement of OGP in regulating osteogenic differentiation of hPDLSCs. In conclusion, OGP at low concentration enhances osteogenic differentiation of hPDLSCs by governing TGF-β signaling pathway.

Stem cells and common biomaterials in dentistry: a review study

Stem cells exist as normal cells in embryonic and adult tissues. In recent years, scientists have spared efforts to determine the role of stem cells in treating many diseases. Stem cells can self-regenerate and transform into some somatic cells. They would also have a special position in the future in various clinical fields, drug discovery, and other scientific research. Accordingly, the detection of safe and low-cost methods to obtain such cells is one of the main objectives of research. Jaw, face, and mouth tissues are the rich sources of stem cells, which more accessible than other stem cells, so stem cell and tissue engineering treatments in dentistry have received much clinical attention in recent years. This review study examines three essential elements of tissue engineering in dentistry and clinical practice, including stem cells derived from the intra- and extra-oral sources, growth factors, and scaffolds.

Osteogenic Commitment of Human Periodontal Ligament Cells Is Predetermined by Methylation, Chromatin Accessibility and Expression of Key Transcription Factors

Periodontal ligament stem cells (PDLCs) can be used as a valuable source in cell therapies to regenerate bone tissue. However, the potential therapeutic outcomes are unpredictable due to PDLCs’ heterogeneity regarding the capacity for osteoblast differentiation and mineral nodules production. Here, we identify epigenetic (DNA (hydroxy)methylation), chromatin (ATAC-seq) and transcriptional (RNA-seq) differences between PDLCs presenting with low (l) and high (h) osteogenic potential. The primary cell populations were investigated at basal state (cultured in DMEM) and after 10 days of osteogenic stimulation (OM). At a basal state, the expression of transcription factors (TFs) and the presence of gene regulatory regions related to osteogenesis were detected in h-PDLCs in contrast to neuronal differentiation prevalent in l-PDLCs. These differences were also observed under stimulated conditions, with genes and biological processes associated with osteoblast phenotype activated more in h-PDLCs. Importantly, even after the induction, l-PDLCs showed hypermethylation and low expression of genes related to bone development. Furthermore, the analysis of TFs motifs combined with TFs expression suggested the relevance of SP1, SP7 and DLX4 regulation in h-PDLCs, while motifs for SIX and OLIG2 TFs were uniquely enriched in l-PDLCs. Additional analysis including a second l-PDLC population indicated that the high expression of OCT4, SIX3 and PPARG TFs could be predictive of low osteogenic commitment. In summary, several biological processes related to osteoblast commitment were activated in h-PDLCs from the onset, while l-PDLCs showed delay in the activation of the osteoblastic program, restricted by the persistent methylation of gene related to bone development. These processes are pre-determined by distinguishable epigenetic and transcriptional patterns, the recognition of which could help in selection of PDLCs with pre-osteoblastic phenotype.

Human periodontal ligament stem cells with distinct osteogenic potential induce bone formation in rat calvaria defects

Aim: This study aimed to evaluate the ability of human periodontal ligament stem cells (PDLSCs) with high (HP-PDLSCs) and low (LP-PDLSCs) osteogenic potential, in addition to mixed cells, to repair bone tissue. Methods: Cell phenotype, proliferation and differentiation were evaluated. Undifferentiated PDLSCs were injected into rat calvarial defects and the new bone was evaluated by μCT, histology and real-time PCR. Results: PDLSCs exhibited a typical mesenchymal stem cell phenotype and HP-PDLSCs showed lower proliferative and higher osteogenic potential than LP-PDLSCs. PDLSCs induced similar bone formation and histological analysis suggests a remodeling process, confirmed by osteogenic and osteoclastogenic markers, especially in tissues derived from defects treated with HP-PDLSCs. Conclusion: PDLSCs induced similar bone formation irrespective of their in vitro osteogenic potential.

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.

The Expression and Regulatory Roles of Long Non-Coding RNAs in Periodontal Ligament Cells: A Systematic Review

Periodontal ligament (PDL) cells play a pivotal role in periodontal and bone homeostasis and have promising potential for regenerative medicine and tissue engineering. There is compelling evidence that long non-coding RNAs (lncRNAs) are differentially expressed in PDL cells compared to other cell types and that these lncRNAs are involved in a variety of biological processes. This study systematically reviews the current evidence regarding the expression and regulatory functions of lncRNAs in PDL cells during various biological processes. A systematic search was conducted on PubMed, the Web of Science, Embase, and Google Scholar to include articles published up to 1 July 2021. Original research articles that investigated the expression or regulation of lncRNAs in PDL cells were selected and evaluated for a systematic review. Fifty studies were ultimately included, based on our eligibility criteria. Thirteen of these studies broadly explored the expression profiles of lncRNAs in PDL cells using microarray or RNA sequencing. Nineteen studies investigated the mechanisms by which lncRNAs regulate osteogenic differentiation in PDL cells. The remaining 18 studies investigated the mechanism by which lncRNAs regulate the responses of PDL cells to various stimuli, namely, lipopolysaccharide-induced inflammation, tumor necrosis factor alpha-induced inflammation, mechanical stress, oxidative stress, or hypoxia. We systematically reviewed studies on the expression and regulatory roles of lncRNAs in diverse biological processes in PDL cells, including osteogenic differentiation and cellular responses to inflammation, mechanical stress, and other stimuli. These results provide new insights that may guide the development of lncRNA-based therapeutics for periodontal and bone regeneration.

Leptin in Dental Pulp and Periapical Tissues: A Narrative Review

Leptin is a non-glycosylated 16 kDa protein synthesized mainly in adipose cells. The main function of leptin is to regulate energy homeostasis and weight control in a central manner. There is increasing evidence that leptin also has systemic effects, acting as a link between innate and acquired immune responses. The expression of leptin and its receptor in human dental pulp and periradicular tissues have already been described, as well as several stimulatory effects of leptin protein expression in dental and periodontal tissues. The aim of this paper was to review and to compile the reported scientific literature on the role and effects of leptin in the dental pulp and periapical tissues. Twelve articles accomplished the inclusion criteria, and a comprehensive narrative review was carried out. Review of the available scientific literature concluded that leptin has the following effects on pulpal and periapical physiology: 1) Stimulates odontogenic differentiation of dental pulp stem cells (DPSCs), 2) Increases the expression of dentin sialophosphoprotein (DSPP) and dentin matrix protein-1 (DMP-1), odontoblastic proteins involved in odontoblastic differentiation and dentin mineralization, 3) Stimulates vascular endothelial growth factor (VEGF) expression in human dental pulp tissue and primary cultured cells of human dental pulp (hDPCs), 4) Stimulates angiogenesis in rat dental pulp cells, and 5) Induces the expression of interleucinas 6 and 8 in human periodontal ligament cells (hPDLCs). There is evidence which suggests that leptin is implicated in the dentin mineralization process and in pulpal and periapical inflammatory and reparative responses.

Tissue Engineering with Compact Bone-Derived Cell Spheroids Enables Bone Formation around Transplanted Tooth

BACKGROUND

Although tooth transplantation is a desirable treatment option for congenital defects of permanent teeth in children, transplantation to a narrow alveolar ridge is not feasible. In this study, we investigated the possibility of bone tissue engineering simultaneously with tooth transplantation to enhance the width of the alveolar bone.

METHODS

Bone marrow mononuclear cells or cortical bone-derived mesenchymal stromal cell spheroids were seeded onto atelocollagen sponge and transplanted with freshly extracted molars from mice of the same strain. New bone formation around the tooth root was evaluated using micro-computed tomography and histological analysis. Tooth alone, or tooth with scaffold but without cells, was also transplanted and served as controls.

RESULTS

Micro-computed tomography showed new bone formation in the furcation area in all four groups. Remarkable bone formation outside the root was also observed in the cortical bone-derived mesenchymal stromal cell group, but was scarce in the other three groups. Histological analysis revealed that the space between the new bone and the root was filled with collagen fibers in all four groups, indicating that the periodontal ligament was maintained.

CONCLUSION

This study demonstrates the potential of simultaneous alveolar bone expansion employing bone tissue engineering approach using cortical bone-derived mesenchymal stromal cell spheroids for tooth transplantation. The use of an orthotopic transplantation model may further clarify the feasibility and functional recovery of the transplanted tooth over a longer period.

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.

Analysis of Three-Dimensional Cell Migration in Dopamine-Modified Poly(aspartic acid)-Based Hydrogels

Several types of promising cell-based therapies for tissue regeneration have been developing worldwide. However, for successful therapeutical application of cells in this field, appropriate scaffolds are also required. Recently, the research for suitable scaffolds has been focusing on polymer hydrogels due to their similarity to the extracellular matrix. The main limitation regarding amino acid-based hydrogels is their difficult and expensive preparation, which can be avoided by using poly(aspartamide) (PASP)-based hydrogels. PASP-based materials can be chemically modified with various bioactive molecules for the final application purpose. In this study, dopamine containing PASP-based scaffolds is investigated, since dopamine influences several cell biological processes, such as adhesion, migration, proliferation, and differentiation, according to the literature. Periodontal ligament cells (PDLCs) of neuroectodermal origin and SH-SY5Y neuroblastoma cell line were used for the in vitro experiments. The chemical structure of the polymers and hydrogels was proved by ¹H-NMR and FTIR spectroscopy. Scanning electron microscopical (SEM) images confirmed the suitable pore size range of the hydrogels for cell migration. Cell viability assay was carried out according to a standardized protocol using the WST-1 reagent. To visualize three-dimensional cell distribution in the hydrogel matrix, two-photon microscopy was used. According to our results, dopamine containing PASP gels can facilitate vertical cell penetration from the top of the hydrogel in the depth of around 4 cell layers (~150 μm). To quantify these observations, a detailed image analysis process was developed and firstly introduced in this paper.

Intranuclear cell uptake and toxicity of titanium dioxide and zirconia particles as well as bacterial adhesion on dental titanium- and zirconia-implants

OBJECTIVE

Previous studies have shown that particles can be released from dental titanium (Ti)- and zirconia (ZrO₂)-implants. Titanium dioxide (TiO₂)- and ZrO₂-particles were compared regarding their toxicity and intranuclear cell uptake as well as the adhesion of various anaerobic bacteria on Ti- and ZrO₂-implants.

METHODS

Cyto- and genotoxicity of TiO₂-microparticles (TiO₂-MPs) and TiO₂-nanoparticles (TiO₂-NPs) in periodontal ligament (PDL)-hTERT cells were determined with XTT test and DNA damage with comet assay. Particle sizes of TiO₂- and ZrO₂-particles were measured with scanning electron microscope. Intranuclear uptake in PDL-hTERT cells was determined with laser scanning confocal microscopy. Adhesions of relevant anaerobic mouth bacteria Porphyromonas gingivalis, Prevotella intermedia and Aggregatibacter actinomycetemcomitans on Ti- and ZrO₂-implants were investigated by cultivation and counting bacterial colonies.

RESULTS

Particle size measurements revealed that 99% of the TiO₂-NPs had a size below 100 nm and 88% of the TiO₂-MPs sizes were between 50 and 200 nm. Following EC₅₀ values were found for particles (mg/l): 92 (TiO₂-MPs) and 15 (TiO₂-NPs). A significant increase in olive tail moment (OTM) was found for TiO₂-NPs at a concentration of 1/10 EC₅₀. TiO₂- and ZrO₂-NPs had a higher intranuclear cell uptake efficiency, compared to corresponding TiO₂- and ZrO₂-MPs. All investigated particles could be detected in cell nucleus. Adhesion of all investigated bacterial species was significantly higher on Ti-implants, compared to ZrO₂-implants.

CONCLUSION

Ti usually develops an oxide layer (TiO₂). Particles released from Ti-implants should be TiO₂-particles or Ti-particles coated with a TiO₂-layer. Toxicity of released Ti-particles depends on their oxidation state and on their size (NP or MP). Particularly, NPs were more cyto- and genotoxic compared to the corresponding MPs. TiO₂- and ZrO₂-NPs showed a significant increase in the intranuclear cell uptake ratio at higher exposure concentration, compared to lower concentrations and consequently might lead to a higher potential of DNA damage. Adhesion of bacteria to ZrO₂-implants is reduced, compared to Ti-implants. Therefore, ZrO₂-implants might contribute to reduced biological complications (e.g. periimplantitis).

Effect of dental antiseptic agents on the viability of human periodontal ligament cells

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Cell viability is key for tissue regeneration.

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Dental antiseptics were cytotoxic in periodontal ligament cells.

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Real-time impedimetry proved to be a non-invasive method to monitor cell viability.

Objectives

We aimed to study whether or not various dental antiseptic agents affect the viability and proliferation of human periodontal ligament cells (PDLCs).

Materials and methods

Human PDLCs were isolated from a total of 10 surgically extracted impacted third molars and were.

cultured in-vitro. The cells were exposed to commonly used dental antiseptics, including chlorhexidine, cetylpyridinium chloride, triclosan, povidone-iodine and sodium bicarbonate for ultra-short-term (10, 20, 30 sec), short-term (10, 20, 30 min) and long-term (24, 48 h) at various concentrations. Cell morphology was observed with light microscopy. Cell viability was studied with impedimetric real-time xCELLigence and resazurin-based alamarBlue® assays. We used one-way ANOVA with Tukey’s and Bonferroni test (p < 0.05) for statistical analysis.

Results

Both alamarBlue® and xCELLigence analysis results were in agreement that ultra-short-term contact with cetylpyridinium chloride ≥ 0.01 mg/ml, chlorhexidine ≥ 1 mg/ml, triclosan ≥ 1 mg/ml and povidone-iodine ≥ 1 mg/ml as well as long-term exposure to cetylpyridinium chloride ≥ 0.001 mg/ml, chlorhexidine ≥ 0.01 mg/ml, triclosan ≥ 1 mg/ml, povidone-iodine ≥ 1 mg/ml and sodium bicarbonate ≥ 10 mg/ml was able to reduce the viability of human PDLCs significantly. According to the half-maximal inhibitory concentration (IC50) the rank of cytotoxicity was cetylpyridinium chloride > chlorhexidine > triclosan > povidone-iodine > sodium bicarbonate.

Conclusions

Our findings suggest that the tested antiseptic agents were cytotoxic to human PDLCs at lower than practically applied concentrations in dental interventions.

The Effect of Diabetes Mellitus on IGF Axis and Stem Cell Mediated Regeneration of the Periodontium

Periodontitis and diabetes mellitus (DM) are two of the most common and challenging health problems worldwide and they affect each other mutually and adversely. Current periodontal therapies have unpredictable outcome in diabetic patients. Periodontal tissue engineering is a challenging but promising approach that aims at restoring periodontal tissues using one or all of the following: stem cells, signalling molecules and scaffolds. Mesenchymal stem cells (MSCs) and insulin-like growth factor (IGF) represent ideal examples of stem cells and signalling molecules. This review outlines the most recent updates in characterizing MSCs isolated from diabetics to fully understand why diabetics are more prone to periodontitis that theoretically reflect the impaired regenerative capabilities of their native stem cells. This characterisation is of utmost importance to enhance autologous stem cells based tissue regeneration in diabetic patients using both MSCs and members of IGF axis.

Calcitriol and enamel matrix derivative differentially regulated cementoinduction and mineralization in human periodontal ligament-derived cells

BACKGROUNDS

Alveolar bone and cementum share many biological and developmental similarities. The mineralizing effect of calcitriol has been previously reported. Yet, its cementoinductivity has not been confirmed. This study evaluated the potential cementoinductivity effect of calcitriol and enamel matrix derivative (EMD) on human periodontal ligament-ligament derived cells (hPDCs).

METHODS

Human PDCs obtained from extracted third molars or premolars were cultured with calcitriol, or EMD. Cementogenic gene expression was examined using RT-qPCR. Expression analysis also included cementoblast-specific markers, Cementum Protein 1 (CEMP1), cementum attachment protein (CAP), and recently reported cementoblast-enriched genes, secreted frizzled related protein 1 (SFRP1), and Dickkopf-related protein 1 (DKK1). Mineralization capacities were evaluated by alkaline phosphatase (ALP) activity, Alizarin Red and Von Kossa staining followed by scanning electron microscope imaging and element mapping.

RESULTS

Among tested conditions, 10 nM calcitriol enhanced most cementogenic gene expression, Trans-forming growth factor-β1 (TGF-β1), bone morphogenetic proteins (BMP-2 and BMP-4), Core-binding factor subunit alpha-1/Runt-related transcription factor 2 (Cbfa1/RUNX2), Type I collagen (Col-1), Alkaline phosphatase (ALP), Bone sialoprotein (BSP), osteopontin (OPN/SPP1), osteocalcin (OCN), CEMP1 and CAP, and Wnt signaling negative modulators, SFRP1 and DKK1, along with highest ALP activity and mineralization formation in hPDCs. However, only moderate CEMP-1 protein was observed. In contrast, EMD stimulated stronger CEMP-1 and CAP protein, but presented weaker mineralization capacity, hinting at the possibility that strong stimulation of mineralization might dominate cemetogenic specific factors and vice versa.

CONCLUSION

Calcitriol demonstrated not only great osteoinductivity, but also the potential to induce cementogenic gene expression by initiating hPDC differentiation and promoting mineralization. Compared to calcitriol, EMD promoted cementoinductivity in hPDCs at a later time point via highly expressed CEMP1 and CAP protein, but with less mineralization. Thus, calcitriol and EMD could provide differential enhancement of cementoinduction and mineralization, likely acting at various differentiation stages. This article is protected by copyright. All rights reserved.

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.

Adipokines in dental pulp: physiological, pathological, and potential therapeutic roles

BACKGROUND

Hundreds of adipokines have been identified, and their extensive range of endocrine functions-regulating distant organs such as oral tissues-and local autocrine/paracrine roles have been studied. In dentistry, however, adipokines are poorly known proteins in the dental pulp; few of them have been studied despite their large number. This study reviews recent advances in the investigation of dental-pulp adipokines, with an emphasis on their roles in inflammatory processes and their potential therapeutic applications.

HIGHLIGHTS

The most recently identified adipokines in dental pulp include leptin, adiponectin, resistin, ghrelin, oncostatin, chemerin, and visfatin. They have numerous physiological and pathological functions in the pulp tissue: they are closely related to pulp inflammatory mechanisms and actively participate in cell differentiation, mineralization, angiogenesis, and immune-system modulation.

CONCLUSION

Adipokines have potential clinical applications in regenerative endodontics and as biomarkers or targets for the pharmacological management of inflammatory and degenerative processes in dental pulp. A promising direction for the development of new therapies may be the use of agonists/antagonists to modulate the expression of the most studied adipokines.

Translational and Clinical Applications of Dental Stem Cell-Derived Exosomes

Mesenchymal stem cells (MSCs) are promising seed cells in tissue repair and regeneration due to their featured properties of self-renewal and multipotency. However, a growing body of evidence has demonstrated that MSCs exert biological functions mainly through secreting exosomes. Exosomes, which contain RNA, proteins, lipids, and metabolites, are new players in regulating many fundamental processes and play important roles in regenerative medicine. Exosomes not only mimic the effects of their parent cells but also possess many advantages such as high drug loading capacity, low immunogenicity, excellent biocompatibility, and low side effects. Currently, a total of 6 different dental stem cells (DSCs) including dental pulp stem cells (DPSCs), stem cells from exfoliated deciduous teeth (SHEDs), periodontal ligament stem cells (PDLSCs), dental follicle progenitor cells (DFPCs), stem cells from apical papilla (SCAPs) and gingival mesenchymal stem cells (GMSCs) have been isolated and identified. DSC-derived exosomes (DSC-Exos) are actively involved in intercellular communication, anti-inflammation, osteogenesis, angiogenesis, immunomodulation, nurturing neurons, and promoting tumor cell apoptosis. In this review, we will critically review the emerging role and clinical application potential of DSC-Exos.

The regulation mechanism of LINC00707 on the osteogenic differentiation of human periodontal ligament stem cells

The osteogenic differentiation of periodontal ligament stem cells (PDLSCs) is important for periodontal tissue repair and regeneration. Long non-coding RNAs (lncRNAs) are key regulators of diverse biological processes. However, their roles in PDLSC osteogenic differentiation are still largely unknown. This study explored the effect of LINC00707 and its mechanism on the osteogenic differentiation of human PDLSCs. Results showed an increase in LINC00707 and forkhead box O1 (FOXO1) but a decrease in miR-490-3p during PDLSC osteogenic differentiation. LINC00707 and FOXO1 promoted osteogenic differentiation as evidenced by the formation of calcium nodules and the increase in osteogenic markers such as alkaline phosphatase, osteocalcin (OCN), and runt-related transcription factor 2 (Runx2). LINC00707 and FOXO1 knockdown exhibited opposite effects. Dual-luciferase reporter assay and qRT-PCR showed that LINC00707 can specially bind to miR-490-3p, which reversed the effect of LINC00707 on PDLSCs. MiR-490-3p inhibitor relieved the inhibiting effect of sh-LINC00707 on osteogenic differentiation. Further investigation revealed that LINC00707 can promote osteogenic differentiation by regulating FOXO1 expression through miR-490-3p sponging. Thus, the LINC00707/miR-490-3p/FOXO1 axis modulated PDLSC osteogenic differentiation and might be a promising therapeutic target for periodontal diseases.

Oral Cavity as a Source of Mesenchymal Stem Cells Useful for Regenerative Medicine in Dentistry

The use of mesenchymal stem cells (MSCs) for regenerative purposes has become common in a large variety of diseases. In the dental and maxillofacial field, there are emerging clinical needs that could benefit from MSC-based therapeutic approaches. Even though MSCs can be isolated from different tissues, such as bone marrow, adipose tissue, etc., and are known for their multilineage differentiation, their different anatomical origin can affect the capability to differentiate into a specific tissue. For instance, MSCs isolated from the oral cavity might be more effective than adipose-derived stem cells (ASCs) for the treatment of dental defects. Indeed, in the oral cavity, there are different sources of MSCs that have been individually proposed as promising candidates for tissue engineering protocols. The therapeutic strategy based on MSCs can be direct, by using cells as components of the tissue to be regenerated, or indirect, aimed at delivering local growth factors, cytokines, and chemokines produced by the MSCs. Here, the authors outline the major sources of mesenchymal stem cells attainable from the oral cavity and discuss their possible usage in some of the most compelling therapeutic frontiers, such as periodontal disease and dental pulp regeneration.