Periodontal ligament-derived cells for periodontal regeneration in animal models: a systematic review

MicroRNA expression in JAG1/Notch-activated periodontal ligament stem cells

OBJECTIVES

The study explored the expression profile of miRNAs in Notch-activated periodontal ligament stem cells (PDLSCs) and examined their potential cellular targets.

METHODS

PDLSCs were cultured and treated with indirect immobilized Jagged1. The miRNA expression profile was examined using NanoString analysis. Bioinformatic analysis was performed together with enrichment, and miRNA expression was evaluated and validated using a quantitative polymerase chain reaction (qPCR).

RESULTS

A total of 26 miRNAs were differentially expressed in Jagged1 treated PDLSCs compared with the controls. Pathway analysis revealed that altered miRNAs were significantly associated with the transforming growth factor β (TGF-β) signaling pathway. Target prediction analysis demonstrated that 11,170 genes as predictable targets of these altered miRNAs. Enrichment of predicted target genes revealed that they were related to ErbB, Ras and MAPK signaling pathways and small GTPase transduction.

CONCLUSIONS

The research concludes that several miRNAs are differentially expressed in jagged-1 treated PDLSCs. In translational terms the differential functionality of these miRNAs offer promise for the development of targeted regenerative materials that are necessary for managing lost tissue replacement in periodontal diseases.

Isolation, identification and osteogenic capability analysis of mesenchymal stem cells derived from different layers of human maxillary sinus membrane

AIM

To discover the populations of mesenchymal stem cells (MSCs) derived from different layers of human maxillary sinus membrane (hMSM) and evaluate their osteogenic capability.

MATERIALS AND METHODS

hMSM was isolated into a monolayer using the combined method of physical separation and enzymatic digestion. The localization of MSCs in hMSM was performed by immunohistological staining and other techniques. Lamina propria layer-derived MSCs (LMSCs) and periosteum layer-derived MSCs (PMSCs) from hMSM were expanded using the explant cell culture method and identified by multilineage differentiation assays, colony formation assay, flow cytometry and so on. The biological characteristics of LMSCs and PMSCs were compared using RNA sequencing, reverse transcription and quantitative polymerase chain reaction, immunofluorescence staining, transwell assay, western blotting and so forth.

RESULTS

LMSCs and PMSCs from hMSMs were both CD73-, CD90- and CD105-positive, and CD34-, CD45- and HLA-DR-negative. LMSCs and PMSCs were identified as CD171+/CD90+ and CD171-/CD90+, respectively. LMSCs displayed stronger proliferation capability than PMSCs, and PMSCs presented stronger osteogenic differentiation capability than LMSCs. Moreover, PMSCs could recruit and promote osteogenic differentiation of LMSCs.

CONCLUSIONS

This study identified and isolated two different types of MSCs from hMSMs. Both MSCs served as good potential candidates for bone regeneration.

Effects of periodontal ligament stem cell-derived exosomes on osteoblastic proliferation, migration, differentiation, apoptosis, and signaling pathways

OBJECTIVE

Periodontitis is characterized by alveolar bone injury and absorption, with high incidence and poor treatment effect. Proliferation, migration, differentiation and apoptosis of osteoblasts are identified as key factors during the regeneration of alveolar bone tissue processes. Periodontal ligament stem cells (PDLSCs) have been proved to be a possible candidate for the treatment of periodontitis due to its multiple advantages, such as increasing the regenerative capacity of bone tissue. However, the effect of exosomes derived from PDLSCs (PDLSC-Exo) on osteoblasts remains to be further studied.

METHODS AND MATERIALS

In this work, cell proliferation, migration, osteogenic differentiation, and H2 O2 -induced apoptosis were detected after cells were exposed to PDLSC-Exo by CCK-8, scratch wound assay, alizarin red S and alkaline phosphatase staining, real-time PCR, flow cytometry, tunel assay, and so on. Moreover, the activation of PI3K/AKT and MEK/ERK signaling pathways was evaluated by western blotting.

RESULTS

We found that PDLSC-Exo are capable of promoting hFOB1.19 cell proliferation, migration and osteogenic differentiation, inhibiting H2 O2 -induced apoptosis, and activating the PI3K/AKT and MEK/ERK signaling pathways.

CONCLUSION

These results suggest that PDLSC-Exo may be a promising therapeutic for osteoblastic damage.

A novel macrolide-Del-1 axis to regenerate bone in old age

Aging is associated with increased susceptibility to chronic inflammatory bone loss disorders, such as periodontitis, in large part due to the impaired regenerative potential of aging tissues. DEL-1 exerts osteogenic activity and promotes bone regeneration. However, DEL-1 expression declines with age. Here we show that systemically administered macrolide antibiotics and a non-antibiotic erythromycin derivative, EM-523, restore DEL-1 expression in 18-month-old ("aged") mice while promoting regeneration of bone lost due to naturally occurring age-related periodontitis. These compounds failed to induce bone regeneration in age-matched DEL-1-deficient mice. Consequently, these drugs promoted DEL-1-dependent functions, including alkaline phosphatase activity and osteogenic gene expression in the periodontal tissue while inhibiting osteoclastogenesis, leading to net bone growth. Macrolide-treated aged mice exhibited increased skeletal bone mass, suggesting that this treatment may be pertinent to systemic bone loss disorders. In conclusion, we identified a macrolide-DEL-1 axis that can regenerate bone lost due to aging-related disease.

CREB1 alleviates the apoptosis and potentiates the osteogenic differentiation of zoledronic acid-treated human periodontal ligament stem cells via up-regulating VEGF

Periodontitis represents a severe inflammatory illness in tooth supporting tissue. It has been supported that cAMP response element binding protein 1 (CREB1), a common transcription factor, extensively participates in osteogenic differentiation. Here, the current study was to look into the impacts of CREB1 on the process of periodontitis and its possible action mechanism. After human periodontal ligament stem cells (PDLSCs) were challenged with zoledronic acid (ZA), CREB1 expression was examined with RT-qPCR and western blotting. CCK-8 assay appraised cell activity. Following CREB1 elevation or/and vascular endothelial growth factor (VEGF) silencing in ZA-treated PDLSCs, CCK-8 and TUNEL assays separately estimated cell viability and apoptosis. Western blotting tested the expression of apoptosis- and osteogenic differentiation-associated proteins. ALP staining measured PDLSCs osteogenic ability and ARS staining estimated mineralized nodule formation. JASPAR predicted the potential binding of CREB1 with VEGF promoter, which was then testified by ChIP and luciferase reporter assays. RT-qPCR and western blotting tested VEGF expression. CREB1 expression was declined in ZA-exposed PDLSCs and CREB1 elevation exacerbated the viability and osteogenic differentiation while obstructed the apoptosis of PDLSCs. Additionally, CREB1 bond to VEGF promoter and transcriptionally activated VEGF expression. Further, VEGF absence partially stimulated the apoptosis while suppressed the osteogenic differentiation of CREB1-overexpressing PDLSCs treated by ZA. To be concluded, CREB1 might activate VEGF transcription to obstruct the apoptosis while contribute to the osteogenic differentiation of ZA-treated PDLSCs.

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.

Screening of functionalized collagen membranes with a porcine periodontal regeneration model

OBJECTIVES

Current methods for periodontal regeneration do not promote collagen fiber insertions into new bone and cementum. We used a pig wound model to screen different functionalized collagen membranes in promoting periodontal reattachment to root surfaces.

METHODS

Treatment groups included (1) control with no membranes, (2) collagen-coated membranes, (3) membranes with insulin-like growth factor-1 (IGF-1), (4) membranes with amelotin, or (5) membranes attached with calcium phosphate cement (CPC), or with CPC combined with IGF-1. Flap procedures were performed on mandibular and maxillary premolars of each pig.

RESULTS

Histomorphometric, micro-CT, and clinical measurements obtained at 4 and 12 weeks after surgery showed cementum formation on denuded roots and reformation of alveolar bone, indicating that the pig model can model healing responses in periodontal regeneration. Calcium phosphate cement simplified procedures by eliminating the need for sutures and improved regeneration of alveolar bone (p < 0.05) compared with other treatments. There was a reduction (p < 0.05) of PD only for the IGF group. Large observed variances between treatment groups indicated that a priori power analyses should be conducted to optimize statistical analysis.

CONCLUSIONS

Pigs can model discrete elements of periodontal healing using collagen-based, functionalized membranes. Screening indicates that membrane anchorage with calcium phosphate cements improve regeneration of alveolar bone.

Stem cells and extracellular vesicles to improve preclinical orofacial soft tissue healing

Orofacial soft tissue wounds caused by surgery for congenital defects, trauma, or disease frequently occur leading to complications affecting patients' quality of life. Scarring and fibrosis prevent proper skin, mucosa and muscle regeneration during wound repair. This may hamper maxillofacial growth and speech development. To promote the regeneration of injured orofacial soft tissue and attenuate scarring and fibrosis, intraoral and extraoral stem cells have been studied for their properties of facilitating maintenance and repair processes. In addition, the administration of stem cell-derived extracellular vesicles (EVs) may prevent fibrosis and promote the regeneration of orofacial soft tissues. Applying stem cells and EVs to treat orofacial defects forms a challenging but promising strategy to optimize treatment. This review provides an overview of the putative pitfalls, promises and the future of stem cells and EV therapy, focused on orofacial soft tissue regeneration.

Biological properties of Ceraputty as a retrograde filling material: an in vitro study on hPDLSCs

OBJECTIVES

To assess the cytocompatibility and bioactive potential of the new calcium silicate-based cement Ceraputty on human periodontal ligament stem cells (hPDLSCs) compared to Biodentine and Endosequence BC root repair material (ERRM).

MATERIALS AND METHODS

hPDLSCs were isolated from extracted third molars from healthy donors. 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, osteo/cemento/odontogenic marker expression via RT-qPCR, and cell calcified nodule formation via Alizarin Red S staining. hPDLSCs cultured in unconditioned or osteogenic media were used as negative and positive control groups, respectively. Statistical analysis was performed using one-way ANOVA or two-way ANOVA and Tukey's post hoc test. Statistical significance was established at p < 0.05.

RESULTS

The highest Ca2+ peak was detected from Biodentine samples, followed by ERRM and Ceraputty. hPDLSC viability was significantly reduced in Ceraputty samples (p < 0.001), while 1:2 and 1:4 Biodentine and ERRM samples similar results to that of the negative control (p > 0.05). Biodentine and ERRM exhibited an upregulation of at least one cemento/odonto/osteogenic marker compared to the negative and positive control groups. Cells cultured with Biodentine produced a significantly higher calcified nodule formation than ERRM and Ceraputty (p < 0.001), which were also higher than the control groups (p < 0.001).

CONCLUSION

Ceraputty evidenced a reduced cytocompatibility towards hPDLSCs on its lowest dilutions compared to the other tested cements and the control group. Biodentine and ERRM promoted a significantly higher mineralization and osteo/cementogenic marker expression on hPDLSCs compared with Ceraputty. Further studies are necessary to verify the biological properties of this new material and its adequacy as a retrograde filling material.

CLINICAL RELEVANCE

This is the first study to elucidate the adequate biological properties of Ceraputty for its use as a retrograde filling material.

Stem cell-based therapy in periodontal regeneration: a systematic review and meta-analysis of clinical studies

BACKGROUND

Periodontitis is a common and chronic inflammatory disease characterized by irreversible destruction of the tooth surrounding tissues, especially intrabony defects, which eventually lead to tooth loss. In recent years, stem cell-based therapy for periodontitis has been gradually applied to the clinic, but whether stem cell-based therapy plays a positive role in periodontal regeneration is unclear at present.

METHODS

The clinical studies related to the evaluation of mesenchymal stem cells for periodontal regeneration in PubMed, Cochrane Central Register of Controlled trials (CENTRAL), Web of Science (WOS), Embase, Scopus, Wanfang and China national knowledge infrastructure (CNKI) databases were searched in June 2023. The inclusion criteria required the studies to compare the efficacy of stem cell-based therapy with stem cell free therapy for the treatment periodontitis, and to have a follow-up for at least six months. Two evaluators searched, screened, and assessed the quality and the risk of bias in the included studies independently. Review Manager 5.4 software was used to perform the meta-analysis, and GRADEpro GDT was used to evaluate the level of the evidence.

RESULTS

Five randomized controlled trials (RCTs) including 118 patients were analyzed. The results of this meta-analysis demonstrated that stem cell-based therapy showed better therapeutic effects on clinical attachment level (CAL) (MD = - 1.18, 95% CI = - 1.55, - 0.80, P < 0.00001), pocket probing depth (PPD) (MD = - 0.75, 95% CI = - 1.35, - 0.14, P = 0.020), and linear distance from bone crest to bottom of defect (BC-BD)( MD = - 0.95, 95% CI = - 1.67, - 0.23, P = 0.010) compared with cell-free group. However, stem cell-based therapy presented insignificant effects on gingival recession (P = 0.14), linear distance from cementoenamel junction to bottom of defect (P = 0.05).

CONCLUSION

The results demonstrate that stem cell-based therapy may be beneficial for CAL, PPD and BC-BD. Due to the limited number of studies included, the strength of the results in this analysis was affected to a certain extent. The high-quality RCTs with large sample size, multi-blind, multi-centric are still required, and the methodological and normative clinical study protocol should be established and executed in the future.

Regenerative Potential of Bone Morphogenetic Protein 7-Engineered Mesenchymal Stem Cells in Ligature-Induced Periodontitis

Periodontitis is an oral disease caused by bacterial infection that has stages according to the severity of tissue destruction. The advanced stage of periodontitis presents irreversible destruction of soft and hard tissues, which finally results in loss of teeth. When conventional treatment modalities show limited results, tissue regeneration therapy is required in patients with advanced periodontitis. In the present study, we aimed to evaluate the effect of bone marrow-derived mesenchymal stem cells (BM-MSCs) delivering bone morphogenetic protein 7 (BMP7) on tissue regeneration in a periodontitis model. BMP7 is a member of the BMP family that shows bone-forming ability; however, BMPs rapid clearing and degradation and unproven efficacy make it difficult to apply it in clinical dentistry. To overcome this, we established BMP7-expressing engineered BM-MSCs (BMP7-eBMSCs) that showed superior osteogenic differentiation potential when subcutaneously transplanted with a biphasic calcium phosphate scaffold into immunocompromised mice. Furthermore, the efficacy of BMP7-eBMSC transplantation for periodontal tissue regeneration was evaluated in a rat ligature-induced periodontitis model. Upon measuring two-dimensional and three-dimensional amounts of regenerated alveolar bone using microcomputed tomography, the amounts were found to be significantly higher in the BMP7-eBMSC transplantation group than in the eBMSC transplantation group. Most importantly, fibrous periodontal ligament (PDL) tissue regeneration was also achieved upon BMP7-eBMSC transplantation, which was evaluated by calculating the modified relative connective tissue attachment. The amount of connective tissue attachment in the BMP7-eBMSC transplantation group was significantly higher than that in the ligature-induced periodontitis group, although the increase was comparable between the BMP7-eBMSC and human PDL stem cell transplantation groups. Taken together, our results suggested that sustainable release of BMP7 induces periodontal tissue regeneration and that transplantation of BMP7-eBMSCs is a feasible treatment option for periodontal regeneration. Impact Statement Periodontitis is the second most common human dental disease affecting chronic systemic diseases. Despite the tremendous efforts trying to cure the damaged periodontal tissues using tissue engineering technologies, a definitive regenerative method has not been in consensus. Researchers are seeking more feasible and abundant source of mesenchymal stem cells (MSCs), and furthermore, how to use reliable growth factors under more efficient control are the issues to be solved. In this study, we aimed to evaluate the effect of bone morphogenetic protein 7 (BMP7) gene delivering bone marrow-derived MSCs on periodontal tissue regeneration to evaluate the efficacy of BMP7 and engineered BMSCs for periodontal tissue regeneration.

Are Endodontic Solvents Cytotoxic? An In Vitro Study on Human Periodontal Ligament Stem Cells

The aim of this study was to assess the influence of eucalyptol, chloroform, and Endosolv on the proliferative capability, cell viability, and migration rates of human periodontal ligament stem cells (hPDLSCs) in vitro. Solvent eluates were formulated following ISO 10993-5 guidelines, and 1%, 0.25%, and 0.1% dilutions were prepared. The HPDLSCs were isolated from the extracted third molars of healthy donors. The following parameters were assessed: cell viability via trypan blue and IC50 assays, cell migration via horizontal wound healing assay, cell morphology via cell cytoskeleton staining (phalloidin labeling), and cell oxidative stress via reactive oxygen species assay. The data were analyzed using one-way ANOVA and Tukey’s posthoc tests, and their significance was established at p < 0.05. Chloroform and eucalyptol exhibited significantly higher cytotoxicity on the hPDLSCs in vitro compared to the control group, as shown by the cell viability, migration, morphology, and reactive oxygen species release assays. Alternatively, Endosolv showed adequate cytotoxicity levels comparable to those of the control group. The cytotoxicity of the tested endodontic solvents increased in a dose-dependent manner. The results from the present study highlight the cytotoxicity of chloroform and eucalyptol. Thus, their limited and cautious use is recommended, avoiding solvent extrusion.

Dual peptide-functionalized hydrogels differentially control periodontal cell function and promote tissue regeneration

Restoring the tooth-supporting tissues lost during periodontitis is a significant clinical challenge, despite advances in both biomaterial and cell-based approaches. This study investigated poly(ethylene glycol) (PEG) hydrogels functionalized with integrin-binding peptides RGD and GFOGER for controlling periodontal ligament cell (PDLC) activity and promoting periodontal tissue regeneration. Dual presentation of RGD and GFOGER within PEG hydrogels potentiated two key PDLC functions, alkaline phosphatase (ALP) activity and matrix mineralization, over either peptide alone and could be tuned to differentially promote each function. Hydrogel matrix mineralization, fostered by high concentrations of GFOGER together with RGD, identified a PDLC phenotype with accelerated matrix adhesion formation and expression of cementoblast and osteoblast genes. In contrast, maximizing ALP activity through high RGD and low GFOGER levels resulted in minimal hydrogel mineralization, in part, through altered PDLC pyrophosphate regulation. Transplantation of PDLCs in hydrogels optimized for either outcome promoted cementum formation in rat periodontal defects; however, only hydrogels optimized for in vitro mineralization improved new bone formation. Overall, these results highlight the utility of engineered hydrogel systems for controlling PDLC functions and their promise for promoting periodontal tissue regeneration.

CTGF Promotes the Osteoblast Differentiation of Human Periodontal Ligament Stem Cells by Positively Regulating BMP2/Smad Signal Transduction

Objective

This work is aimed at revealing the role and the molecular mechanism of connective tissue growth factor 2 (CTGF) in the osteoblast differentiation of periodontal ligament stem cells (PDLSCs).

Methods

The osteogenic differentiation of PDLSCs was induced by osteogenic induction medium (OM), and the expression level of osteogenic related proteins ALP, RUNX2, OCN, and CTGF was estimated using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting analysis. We constructed cell lines with CTGF overexpression or knockdown to verify the role of CTGF in the osteoblast differentiation of PDLSCs. Alkaline phosphatase (ALP) staining was introduced to measure the osteoblasts activity, and alizarin red S (ARS) staining was employed to test matrix mineralization. The interaction between CTGF and bone morphogenetic protein-2 (BMP-2) was determined by endogenous coimmunoprecipitation (Co-IP).

Results

The expression level of CTGF was increased during the osteogenic induction of PDLSCs. Additionally, CTGF overexpression effectively maintained the stemness and facilitated the osteoblast differentiation in PDLSCs, and CTGF knockdown exerted opposite effects. Moreover, at molecular mechanism, CTGF increased the activity of BMP-2/Smad signaling pathway.

Conclusion

This investigation verified that CTGF promotes the osteoblast differentiation in PDLSCs at least partly by activating BMP-2/Smad cascade signal.

Diverse stem cells for periodontal tissue formation and regeneration

The periodontium is comprised of multiple units of mineralized and nonmineralized tissues including the cementum on the root surface, the alveolar bone, periodontal ligament (PDL), and the gingiva. PDL contains a variety of cell populations including mesenchymal stem/progenitor cells (MSCs) termed PDLSCs, which contribute to periodontal regeneration. Recent studies utilizing mouse genetic models shed light on the identities of these mesenchymal progenitors in their native environment, particularly regarding how they contribute to homeostasis and repair of the periodontium. The current concept is that mesenchymal progenitors in the PDL are localized to the perivascular niche. Single-cell RNA sequencing (scRNA-seq) analyses reveal heterogeneity and cell-type specific markers of cells in the periodontium, as well as their developmental relationship with precursor cells in the dental follicle. The characteristics of PDLSCs and their diversity in vivo are now beginning to be unraveled thanks to insights from mouse genetic models and scRNA-seq analyses, which aid to uncover the fundamental properties of stem cells in the human PDL. The new knowledge will be highly important for developing more effective stem cell-based regenerative therapies to repair periodontal tissues in the future.

Comparative evaluation of combined efficacy of methylene blue mediated antimicrobial photodynamic therapy (a-PDT) using 660 nm diode laser versus Erbium-chromium-yttrium-scandium-gallium-garnet (Er, Cr: YSGG) laser as an adjunct to scaling and root planing on clinical parameters in supportive periodontal therapy: A randomized split-mouth trial

AIM

The aim of this study was to evaluate combined efficacy of methylene blue mediated antimicrobial photodynamic therapy (a-PDT) using 660 nm diode laser versus Er, Cr: YSGG laser as an adjunct to scaling and root planing on improving the Probing depth (PD), Clinical attachment level (CAL), Plaque Index (PI) and Gingival Index (GI).clinical parameters in Supportive periodontal therapy.

MATERIALS AND METHOD

In this split-mouth, double-blind, randomized controlled trial, we compared a-PDT versus Er,Cr:YSGG as an adjunct to scaling and root planning (SRP) with SRP alone in Supportive periodontal therapy. A total of 36 subjected were enrolled. In each patient, two quadrants constituted the control group (Group I - Scaling and root planing SRP alone), one site in other quadrant constituted the test group 1 (Group II - SRP followed by application of Er, Cr: YSGG laser), and another site in different quadrant constituted the test group 2 (Group III - SRP followed by antimicrobial Photodynamic therapy using diode laser). The diode laser was operated at a peak power of 70 mW using a 0.6 mm diameter fiber-optic tip. Each site was irradiated with a power density of 28 mW/cm², for 10 s, thus delivering a total energy of 16.72 J/cm² per tooth. Whereas, the Er,Cr:YSGG laser's parameters were set to 1 W of power, 10% air, and 15% water. The same procedure was repeated at 1st, 2nd and 3rd week for both the laser therapies. Plaque index (PI), Gingival index (GI), Probing depth (PD,) and Clinical attachment level (CAL) were measured by a single examiner at baseline and 3 months follow up. Inter group analysis of the parameters were done using One-way ANOVA and pairwise comparison was carried out by Tukey's post hoc test. Intra group analysis was performed using Students's paired t test. Statistical significance was set to p < 0.05.

RESULTS

There were no significant differences between participants for clinical parameters at baseline. PI, GI PD, and CAL significantly improved at 3 months follow up compared to baseline in both the study groups (Group II - SRP + Er,Cr:YSGG, Group III - SRP + a-PDT) with P < 0.05. Adjunctive use of Er,Cr:YSGG laser with SRP showed better clinical outcomes than a-PDT with SRP.

CONCLUSION

Nonsurgical periodontal therapy of chronic periodontitis using Er, Cr: YSGG, and a-PDT as an adjunct to SRP was significantly more effective than SRP alone in reducing PD, CAL, GI, and PI at 3 months follow up. Adjunctive use of Er,Cr:YSGG laser with SRP showed better clinical outcomes than a-PDT with SRP. However, the long-term positive benefits of the laser therapies are yet unknown and more research with longer follow-ups are required.

miR-141-3p Regulates EZH2 to Attenuate Porphyromonas gingivalis Lipopolysaccharide-Caused Inflammation and Inhibition of Osteogenic Differentiation in Human Periodontal Ligament Stem Cells

Objective

miR-141-3p has been demonstrated to be both anti-inflammatory and osteoprotective. This study is aimed at investigating the effect of miR-141-3p on osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) stimulated by Porphyromonas gingivalis lipopolysaccharide (PgLPS) and its mechanism.

Methods

PgLPS was used to induce an inflammatory environment, and overexpression of miR-141-3p was done to assess its effect on hPDLSCs in an inflammatory environment. The level of miR-141-3p and EZH2 in hPDLSCs from each treatment group was detected via qRT-PCR, and the inflammatory factors IL-6 and IL-8 in the supernatant of each group were detected by ELISA. ALP staining and alizarin red staining were used to assess the effect of miR-141-3p on the osteogenic differentiation ability of hPDLSCs, and also, western blot was used to detect expression of osteogenic differentiation-related proteins. Further, dual-luciferase reporter assay examined whether miR-141-3p targeted EZH2.

Results

PgLPS led to a significant decrease of miR-141-3p in hPDLSCs. Overexpression of miR-141-3p could enhance ALP activity and alizarin red staining intensity and increase Runx2, OPN and OCN protein expression levels in PgLPS-treated hPDLSCs. Additionally, miR-141-3p could reduce IL-6 and IL-8. miR-141-3p could target and negatively regulate EZH2, and overexpression of EZH2 reversed the promoting effect of miR-141-3p on osteogenic differentiation.

Conclusion

miR-141-3p can attenuate PgLPS-induced inhibition of osteogenic differentiation and inflammation in hPDLSCs by negatively regulating EZH2.

Influence of Periodontal Ligament Stem Cell-Derived Conditioned Medium on Osteoblasts

Mesenchymal stem cells (MSC) are involved in the regeneration of various missing or compromised periodontal tissues, including bone. MSC-derived conditioned medium (CM) has recently been explored as a favorable surrogate for stem cell therapy, as it is capable of producing comparable therapeutic effects. This study aimed to evaluate the influence of periodontal ligament stem cells (PDLSC)-CM on osteoblasts (OB) and its potential as a therapeutic tool for periodontal regeneration. Human PDLSC were isolated and characterized, and CM from these cells was collected. The presence of exosomes in the culture supernatant was observed by immunofluorescence and by transmission electron microscopy. CM was added to a cultured osteoblastic cell line (Saos-2 cells) and viability (MTT assay) and gene expression analysis (real-time PCR) were examined. A cell line derived from the periodontal ligament and showing all the characteristics of MSC was successfully isolated and characterized. The addition of PDLSC-CM to Saos-2 cells led to an enhancement of their proliferation and an increased expression of some osteoblastic differentiation markers, but this differentiation was not complete. Saos-2 cells were involved in the initial inflammation process by releasing IL-6 and activating COX2. The effects of PDLSC-CM on Saos-2 appear to arise from a cumulative effect of different effective components rather than a few factors present at high levels.

Periodontal Wound Healing and Regeneration: Insights for Engineering New Therapeutic Approaches

Periodontitis is a widespread inflammatory disease that leads to loss of the tooth supporting periodontal tissues. The few therapies available to regenerate periodontal tissues have high costs and inherent limitations, inspiring the development of new approaches. Studies have shown that periodontal tissues have an inherent capacity for regeneration, driven by multipotent cells residing in the periodontal ligament (PDL). The purpose of this review is to describe the current understanding of the mechanisms driving periodontal wound healing and regeneration that can inform the development of new treatment approaches. The biologic basis underlying established therapies such as guided tissue regeneration (GTR) and growth factor delivery are reviewed, along with examples of biomaterials that have been engineered to improve the effectiveness of these approaches. Emerging therapies such as those targeting Wnt signaling, periodontal cell delivery or recruitment, and tissue engineered scaffolds are described in the context of periodontal wound healing, using key in vivo studies to illustrate the impact these approaches can have on the formation of new cementum, alveolar bone, and PDL. Finally, design principles for engineering new therapies are suggested which build on current knowledge of periodontal wound healing and regeneration.

Stem Cell Transplantation and Cell-Free Treatment for Periodontal Regeneration

Increasing attention has been paid to cell-based medicines. Many in vivo and in vitro studies have demonstrated the efficacy of stem cell transplantation for the regeneration of periodontal tissues over the past 20 years. Although positive evidence has accumulated regarding periodontal regeneration using stem cells, the exact mechanism of tissue regeneration is still largely unknown. This review outlines the practicality and emerging problems of stem cell transplantation therapy for periodontal regeneration. In addition, possible solutions to these problems and cell-free treatment are discussed.

Comparison of cellular and differentiation characteristics of mesenchymal stem cells derived from human gingiva and periodontal ligament

Objectives:

Dental tissues possess multipotent stem cells with varying biological properties. The present study was aimed to establish a primary culture of human gingiva-derived mesenchymal stem cells (GMSCs) and periodontal ligament-derived stem cells (PDLSCs) from periodontally healthy subjects and compare their biological characteristics.

Materials and Methods:

Gingival and periodontal ligament (PDL) tissues were collected from extracted premolar teeth of five healthy subjects and primary cultures were established. Basic biological characteristics, such as cell morphology, viability, proliferation capacity, and colony-forming units, and in vitro osteogenic and adipogenic differentiation potential were performed at passage 3 of GMSCs and PDLSCs. This was followed by immuno-phenotyping and flow cytometric analysis for identification of positive mesenchymal stem cell (MSC) markers, such as CD73, CD90, and CD105, and negative markers CD45 and CD34.

Statistical Analysis Used:

One-way analysis of variance (ANOVA).

Results:

Primary cultures of GMSCs and PDLSCs were successfully established. Cells exhibited a fibroblast-like morphology with a homogeneous population at passage 3. Cells derived from both tissues were highly viable (>95%), proliferative, and capable of forming colonies. Both cells did not exhibit any noticeable differences in cellular properties. Immunofluorescence and flow cytometric analyses showed positivity for MSC markers, CD73, CD90, and CD105, and negativity for CD34 and CD45. Furthermore, GMSCs and PDLSCs were capable of differentiating in vitro into osteocytes as evidenced by Alizarin red-S staining, and adipocytes as demonstrated by oil red O staining.

Conclusions:

The results of the present study indicate that both GMSCs and PDLSCs have similar cellular characteristics and mesenchymal differentiation potential. Therefore, they may serve as an equally potent source of stem cells for use in cell-based periodontal therapies.

Stem Cell Applications in Periodontal Regeneration

In this review, the authors consider the substantial advances that have been made in recent years in stem cell-based periodontal regeneration. These advances involve identifying dental- and nondental-derived stem cells with the capacity to modulate periodontal regeneration, human clinical trials, and emerging concepts, including cell banking, good manufacturing processes, and overall clinical translation.

Characterization and evaluation of ascorbic acid-induced cell sheet formation in human periodontal ligament stem cells: An in vitro study

OBJECTIVES

Periodontal ligament-derived stem cells (PDLSCs) are regarded as a viable option for periodontal regeneration using cell sheet technology. The objective of the present in vitro study was to characterize human PDLSCs based on their phenotypic and biological properties and to evaluate the ascorbic acid (AA or vitamin C)-induced cell sheet by analyzing the molecular markers.

METHODS

PDLSCs were established from premolars, and their morphology, viability, proliferation, phenotypic marker expression, and ability to differentiate into osteocytes and adipocytes were analyzed. PDLSCs were then induced to form cell sheets using 100 μM AA, and gene expression was examined by real-time polymerase chain reaction.

RESULTS

PDLSCs showed fibroblastic morphology with >95% viability. The cells were highly proliferative and positive for surface antigens CD29, CD73, and CD90 but negative for CD34 and CD45. They were capable of differentiating into osteocytes and adipocytes. Induction with 100 μM AA transformed PDLSCs into two-to three-layered cell sheets. There was no significant upregulation in ALP and RUNX2 expression in the AA-induced cell sheet. However, the expression levels of late osteoblast differentiation marker (bone gamma-carboxy glutamate protein); cementogenic markers (cementum attachment protein and CP23), and genes encoding extracellular matrix (ECM) proteins [collagen type 1 alpha 1 and integrin beta 1) were higher in AA-induced cell sheets by PDLSCs.

CONCLUSIONS

The stimulating effect of AA on cell sheet formation by PDLSCs was confirmed by the expression of typical markers involved in osteogenesis/cementogenesis and ECM secretion, which makes this procedure a prospective option for periodontal tissue regeneration applications.

Autotransplantation of the Third Molar: A Therapeutic Alternative to the Rehabilitation of a Missing Tooth: A Scoping Review

INTRODUCTION

Tooth autotransplantation is the repositioning of an erupted, partially erupted, or non-erupted autologous tooth from one site to another within the same individual. Several factors influence the success rate of the autotransplant, such as the stage of root development, the morphology of the tooth, the surgical procedure selected, the extraoral time, the shape of the recipient socket, the vascularity of the recipient bed, and the vitality of the cells of the periodontal ligament. The aim of this scoping review was to provide the most up-to-date information and data on the clinical principles of the third-molar autograft and thus provide clinical considerations for its success.

MATERIALS AND METHODS

This review was conducted based on PRISMA-ScR (Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews). The research was conducted by searching for keywords in three databases-PubMed, Scopus and Google Scholar-by two independent reviewers following the PRISMA protocol, from which 599 records were identified.

CONCLUSIONS

Third-molar autotransplantation is a valid solution to replace missing teeth. The key to the success of this technique is the surgical procedure, which must be as atraumatic as possible to preserve the periodontal ligament of the tooth to be transplanted. The success rate is also linked to the stage of development of the root, with a worse prognosis in the case of a complete root.

Biological interactions between calcium silicate-based endodontic biomaterials and periodontal ligament stem cells: A systematic review of in vitro studies

BACKGROUND

Most recently, the biological interactions, that is cytocompatibility, cell differentiation and mineralization potential, between calcium silicate-based biomaterials and periodontal ligament stem cells (PDLSCs) have been studied at an in vitro level, in order to predict their clinical behaviour during endodontic procedures involving direct contact with periodontal tissues, namely root canal treatment, endodontic surgery and regenerative endodontic treatment.

OBJECTIVE

The aim of the present systematic review was to present a qualitative synthesis of available in vitro studies assessing the biological interaction of PDLSCs and calcium silicate-based biomaterials.

METHODOLOGY

The present review followed PRISMA 2020 guidelines. An advanced database search was performed in Medline, Scopus, Embase, Web of Science and SciELO on 1 July 2020 and last updated on 22 April 2021. Studies assessing the biological interactions of PDLSCs with calcium silicate-based sealers (CSSs) and/or cements (CSCs) at an in vitro level were considered for inclusion. The evaluation of the 'biological interaction' was defined as any assay or test on the cytotoxicity, cytocompatibility, cell plasticity or differentiation potential, and bioactive properties of PDLSCs cultured in CSC or CSS-conditioned media. Quality (risk of bias) was assessed using a modified CONSORT checklist for in vitro studies of dental materials.

RESULTS

A total of 20 studies were included for the qualitative synthesis. CSCs and CSSs, as a group of endodontic materials, exhibit adequate cytocompatibility and favour the osteo/cementogenic differentiation and mineralization potential of PDLSCs, as evidenced from the in vitro studies included in the present systematic review.

DISCUSSION

The influence of the compositional differences, inclusion of additives, sample preparation, and varying conditions and manipulations on the biological properties of calcium silicate-based materials remain a subject for future research.

CONCLUSIONS

Within the limitations of the in vitro nature of the included studies, this work supports the potential use of calcium silicate-based endodontic materials in stem cell therapy and biologically based regenerative endodontic procedures.

REGISTRATION

OSF Registries; https://doi.org/10.17605/OSF.IO/SQ9UY.

Decellularized matrix could affect the proliferation and differentiation of periodontal ligament stem cells in vitro

OBJECTIVE AND BACKGROUND

Recently, decellularized matrix (DCM) is considered as a new biomaterial for tissue regeneration. To explore the possible application of DCM in periodontal regeneration, the effect of DCM from three different cells on the proliferation and differentiation of human periodontal ligament stem cells (PDLSCs) was investigated.

METHODS

DCM derived from human periodontal ligament cells (PDLCs), dental pulp cells (DPCs), and gingival fibroblasts (GFs) were fabricated using Triton X-100/NH₄ OH combined with DNase I. Allogeneic PDLSCs were cultured on PDLC-DCM, DPC-DCM, and GF-DCM, respectively. The proliferative capacity of PDLSCs was evaluated by PicoGreen assay kit. The expression of alkaline phosphatase (ALP), runt-related transcription factor-2 (RUNX2), osteocalcin (OCN), collagen I (COL1), periostin (POSTN), and cementum protein 1 (CEMP1) were detected by qRT-PCR and western blotting.

RESULTS

PDLC-DCM, DPC-DCM, and GF-DCM had similar and integrated networks of extracellular matrix, as well as significantly decreased DNA content. Compared with control group in which PDLSCs were directly seeded in culture plates, PDLC-DCM, DPC-DCM, and GF-DCM promoted the proliferation of re-seeded PDLSCs. Additionally, PDLSCs on DCM exhibited higher mRNA and protein expression levels of ALP, RUNX2, OCN, and COL1. The expression of POSTN in PDLC-DCM group was significantly higher than control group at both mRNA and protein levels.

CONCLUSIONS

PDLC-DCM, DPC-DCM, and GF-DCM could enhance the proliferation of PDLSCs. PDLC-DCM facilitated osteogenic differentiation and periodontal ligament differentiation of PDLSCs, while DPC-DCM and GF-DCM promoted osteogenic differentiation.

The effect of LED photobiomodulation on the proliferation and osteoblastic differentiation of periodontal ligament stem cells: in vitro

BACKGROUND

The aim of this study was to investigate the influence of three different light-emitting diode (LED) wavelengths on the proliferation and osteoblastic differentiation of periodontal ligament stem cells (PDLSCs) in vitro.

METHODS

PDLSCs seeded on 96- and 24-well plates, for proliferation and osteoblastic differentiation, respectively, were irradiated daily by LED light with peak emission wavelengths of 630, 680, and 830 nm at constant energy densities of 3.5 J/cm². Cultures were grown for 8 days for the proliferation assay, 10 days for the alkaline phosphatase (ALP) assay, and 28 days for Alizarin red staining. Mitochondrial activity, ALP enzyme level, and the ability to form calcium phosphate deposits were measured and compared across cultures.

RESULTS

Results obtained from statistical analysis of the experimental data indicated that the rate of proliferation (P < 0.05) in 830-nm irradiated cultures were significantly higher than the control samples at day 6 and 8; whereas, for the 630- and 680-nm groups, test results showed lower proliferation rates at day 8. For osteoblastic differentiation, significantly greater mineralization than the control samples was detected in the red-light groups (630 and 680 nm) during the late differentiation period (P < 0.001), which was supported by a higher ALP activity of the 630- and 680-nm groups in the early stage (P < 0.01).

CONCLUSION

The results of this study demonstrate that the PDLSCs responded differently to specific LED wavelengths. For enhancing cellular proliferation, 830-nm LED irradiation was more effective. On the other hand, the wavelengths of 630 and 680 nm were better for stimulating osteoblastic differentiation.

CDR1as regulated by hnRNPM maintains stemness of periodontal ligament stem cells via miR-7/KLF4

CDR1as is a well‐identified circular RNA with regulatory roles in a variety of physiological processes. However, the effects of CDR1as on stemness of periodontal ligament stem cells (PDLSCs) and the underlying mechanisms remain unclear. In this study, we detect CDR1as in human PDLSCs, and subsequently demonstrate that CDR1as maintains PDLSC stemness. Knockdown of CDR1as decreases the expression levels of stemness‐related genes and impairs the cell's multi‐differentiation and cell migration abilities, while overexpression of CDR1as increases the expression levels of stemness‐related genes and enhances these abilities. Furthermore, our results indicate that the RNA‐binding protein hnRNPM directly interacts with CDR1as and regulates its expression in PDLSCs. In addition, we show that CDR1as promotes the expression of stemness‐related genes in PDLSCs by inhibiting miR‐7‐mediated suppression of KLF4 expression. Collectively, our results demonstrate that CDR1as participates in the molecular circuitry that regulates PDLSC stemness.

Cell-Based Therapy for Tooth Replantation Following Avulsion: A Systematic Review

The management of avulsed teeth undergoing delayed replantation remains a clinical challenge as there are currently no effective interventions that can improve periodontal healing and prevent replacement root resorption. While several preclinical studies have reported varied success using cell-based tissue engineering to improve periodontal healing, a consensus is required before further clinical translation. Therefore, this systematic review seeks to evaluate the efficacy of cell-based therapy in promoting periodontal healing following delayed replantation in animal models. MEDLINE (PubMed) and Embase were searched on September 27, 2020. Ten studies involving rodent and dog models met the inclusion criteria. Cell sources included gingiva, periodontal ligament (PDL), bone marrow, and adipose tissues. Generally, cell-based therapy had increased the proportion of root surfaces displaying periodontal healing and concomitantly reduced the proportion presenting with replacement root resorption and ankylosis. The best outcomes were observed following treatment with PDL-derived cells of various potency. Future preclinical studies will benefit from adopting measures to minimize bias during the conduct of animal experiments and the standardization of the outcome measures reporting. This will facilitate future reviews with possible pooling of results in the form of meta-analyses, allowing a consensus to be obtained from the literature. In addition, further research will be required to shed light on the implications of using allogeneic cells as well as the optimization of cell delivery protocols. The findings of this systematic review demonstrated the therapeutic potential of certain cell-based therapies in promoting periodontal healing following delayed replantation, thus highlighting their prospective clinical benefits and translational value.

Periodontal regeneration using a xenogeneic bone substitute seeded with autologous periodontal ligament-derived mesenchymal stem cells: A 12-month quasi-randomized controlled pilot clinical trial

AIM

To evaluate the safety and efficacy of autologous periodontal ligament-derived mesenchymal stem cells (PDL-MSCs) embedded in a xenogeneic bone substitute (XBS) for the regenerative treatment of intra-bony periodontal defects.

MATERIAL AND METHODS

This quasi-randomized controlled pilot phase II clinical trial included patients requiring a tooth extraction and presence of one intra-bony lesion (1-2 walls). Patients were allocated to either the experimental (XBS + 10 × 10⁶ PDL-MSCs/100 mg) or the control group (XBS). Clinical and radiographical parameters were recorded at baseline, 6, 9 and 12 months. The presence of adverse events was also evaluated. Chi-square, Student's t test, Mann-Whitney U, repeated-measures ANOVA and regression models were used.

RESULTS

Twenty patients were included. No serious adverse events were reported. Patients in the experimental group (n = 9) showed greater clinical attachment level (CAL) gain (1.44, standard deviation [SD] = 1.87) and probing pocket depth (PPD) reduction (2.33, SD = 1.32) than the control group (n = 10; CAL gain = 0.88, SD = 1.68, and PPD reduction = 2.10, SD = 2.46), without statistically significant differences.

CONCLUSION

The application of PDL-MSCs to XBS for the treatment of one- to two-wall intra-bony lesions was safe and resulted in low postoperative morbidity and appropriate healing, although its additional benefit, when compared with the XBS alone, was not demonstrated.

Mesenchymal stem cell-derived small extracellular vesicles as cell-free therapy: Perspectives in periodontal regeneration

Mesenchymal stem cells (MSC) are involved in the regeneration of the different missing or compromised periodontal tissues. MSC-derived small extracellular vesicles (sEV) have recently been explored as a favorable substitution for stem cell therapy, as they are capable of producing therapeutic effects comparable to those of their parent cells, with advantages over cell therapy. The aim of this review is to evaluate the use of mesenchymal stem cells (MSC)-derived sEV as cell-free therapy in periodontal regeneration. A review of the scientific literature on sEV and their use in periodontal regeneration was performed. The main characteristics of sEV are described, and their mechanisms of action and potential biological effects in periodontal regeneration are studied. A summary of existing preclinical studies conducted in animals is performed. The results indicate that sEV derived from MSC are emerging as a promising new therapeutic tool in the field of periodontal regeneration and may become an ideal therapeutic option. In this review, we have summarized recent advances in this regard in order to better understand this newly emerging treatment. First results in vivo are promising and show a favorable potential for cell-free therapy in periodontal regeneration.

Role and application of stem cells in dental regeneration: A comprehensive overview

Recently, a growing attention has been observed toward potential advantages of stem cell (SC)-based therapies in regenerative treatments. Mesenchymal stem/stromal cells (MSCs) are now considered excellent candidates for tissue replacement therapies and tissue engineering. Autologous MSCs importantly contribute to the state-of-the-art clinical strategies for SC-based alveolar bone regeneration. The donor cells and immune cells play a prominent role in determining the clinical success of MSCs therapy. In line with the promising future that stem cell therapy has shown for tissue engineering applications, dental stem cells have also attracted the attention of the relevant researchers in recent years. The current literature review aims to survey the variety and extension of SC-application in tissue-regenerative dentistry. In this regard, the relevant English written literature was searched using keywords: "tissue engineering", "stem cells", "dental stem cells", and "dentistry strategies". According to the available database, SCs application has become increasingly widespread because of its accessibility, plasticity, and high proliferative ability. Among the growing recognized niches and tissues containing higher SCs, dental tissues are evidenced to be rich sources of MSCs. According to the literature, dental SCs are mostly present in the dental pulp, periodontal ligament, and dental follicle tissues. In this regard, the present review has described the recent findings on the potential of dental stem cells to be used in tissue regeneration.

Quercetin reverses TNF‑α induced osteogenic damage to human periodontal ligament stem cells by suppressing the NF‑κB/NLRP3 inflammasome pathway

Quercetin (Quer) is a typical antioxidant flavonoid from plants that is involved in bone metabolism, as well as in the progression of inflammatory diseases. Elevated levels of tumor necrosis factor-α (TNF-α), a typical pro-inflammatory cytokine, can affect osteogenesis. In the present study, TNF-α was used to establish an in vitro model of periodontitis. The effects of Quer on, as well as its potential role in the osteogenic response of human periodontal ligament stem cells (hPDLSCs) under TNF-α-induced inflammatory conditions and the underlying mechanisms were then investigated. Within the appropriate concentration range, Quer did not exhibit any cytotoxicity. More importantly, Quer significantly attenuated the TNF-α induced the suppression of osteogenesis-related genes and proteins, alkaline phosphatase (ALP) activity and mineralized matrix in the hPDLSCs. These findings were associated with the fact that Quer inhibited the activation of the NF-κB signaling pathway, as well as the expression of NLRP3 inflammation-associated proteins in the inflammatory microenvironment. Moreover, the silencing of NLRP3 by small interfering RNA (siRNA) was found to protect the hPDLSCs against TNF-α-induced osteogenic damage, which was in accordance with the effects of Quer. On the whole, the present study demonstrates that Quer reduces the impaired osteogenesis of hPDLSCs under TNF-α-induced inflammatory conditions by inhibiting the NF-κB/NLRP3 inflammasome pathway. Thus, Quer may prove to be a potential remedy against periodontal bone defects.

Angiogenic Effects of Secreted Factors from Periodontal Ligament Stem Cells

Periodontal disease is a chronic inflammation of tooth-supporting tissues, and the destruction of these tissues results in tooth loss. Regeneration of periodontal tissues is the ultimate goal of periodontal treatment. We previously reported that transplantation of conditioned medium (CM) of periodontal ligament stem cells (PDLSCs) demonstrated the enhancement of periodontal tissue regeneration, compared to CM from fibroblasts (Fibroblast-CM). We hypothesized that the angiogenic effects of PDLSC-CM might participate in the enhanced wound healing of periodontal tissues. The aim of this study was to investigate the effect of PDLSC-CM on the functions of endothelial cells. PDLSCs were cultured from periodontal ligament tissues obtained from healthy volunteers. Human gingival epithelial cells, dermal fibroblasts, osteoblasts, and umbilical vein endothelial cells (HUVECs) were purchased from commercial sources. The functions of endothelial cells were examined using immunostaining of Ki67, observation of nuclear fragmentation and condensation (apoptosis), and network formation on Matrigel. Vascular endothelial cell growth factor (VEGF) level was measured using an ELISA kit. HUVECs demonstrated higher cell viability in PDLSC-CM when compared with those in Fibroblast-CM. HUVECs demonstrated a higher number of Ki67-positive cells and lower apoptosis cells in PDLSC-CM, compared to Fibroblast-CM. Additionally, HUVECs formed more capillary-like structures in PDLSC-CM than Fibroblast-CM. PDLSC-CM contained higher levels of angiogenic growth factor, VEGF, than Fibroblast-CM. Our results showed that PDLSC-CM increased cell viability, proliferation, and capillary formation of HUVECs compared to Fibroblast-CM, suggesting the angiogenic effects of PDLSC-CM, and the effect is a potential regenerative mechanism of periodontal tissues by PDLSC-CM.

In Vivo Study for Clinical Application of Dental Stem Cell Therapy Incorporated with Dental Titanium Implants

The aim of this study was to investigate the behavior of dental-derived human mesenchymal stem cells (d-hMSCs) in response to differently surface-treated implants and to evaluate the effect of d-hMSCs on local osteogenesis around an implant in vivo. d-hMSCs derived from alveolar bone were established and cultured on machined, sandblasted and acid-etched (SLA)-treated titanium discs with and without osteogenic induction medium. Their morphological and osteogenic potential was assessed by scanning electron microscopy (SEM) and real-time polymerase chain reaction (RT-PCR) via mixing of 5 × 10⁶ of d-hMSCs with 1 mL of Metrigel and 20 μL of gel-cell mixture, which was dispensed into the defect followed by the placement of customized mini-implants (machined, SLA-treated implants) in New Zealand white rabbits. Following healing periods of 2 weeks and 12 weeks, the obtained samples in each group were analyzed radiographically, histomorphometrically and immunohistochemically. The quantitative change in osteogenic differentiation of d-hMSCs was identified according to the type of surface treatment. Radiographic analysis revealed that an increase in new bone formation was statistically significant in the d-hMSCs group. Histomorphometric analysis was in accordance with radiographic analysis, showing the significantly increased new bone formation in the d-hMSCs group regardless of time of sacrifice. Human nuclei A was identified near the area where d-hMSCs were implanted but the level of expression was found to be decreased as time passed. Within the limitations of the present study, in this animal model, the transplantation of d-hMSCs enhanced the new bone formation around an implant and the survival and function of the stem cells was experimentally proven up to 12 weeks post-sacrifice.

Regenerative periodontal therapy: I part

Introduction: Under the concept of regenerative periodontal therapy, there are two approaches: the first is the passive regeneration conceptthat includes bone substituents and guided periodontal regeneration by using of biomembranes and the second concept of active regeneration that impliesthe use of growth factors. The aim of the passive regeneration, by using of bone matrix (bone substituens) has been stabilization and bone defects management, preventing epithelial tissue growth, as well as saving space for the new tissue regeneration. This concept implies the use of autogenous transplantats, xenografts, allografts, as well as alloplastic materials. The carriers for active tissue regeneration, growth factors -GF are biological mediators that regulate cellular processes and that is crucial for the tissue regeneration. Aim:Presentation ofmodern approaches to periodontal therapy thatare focused on the attachment regeneration and complete reconstruction of periodontal tissue. Conclusion: In the future, periodontal regenerative therapy with periodontalligament progenitor cells should encourage repopulation of the areas that have been affected by periodontal disease.

Clinical Application of Bone Marrow Mesenchymal Stem/Stromal Cells to Repair Skeletal Tissue

There has been an escalation in reports over the last decade examining the efficacy of bone marrow derived mesenchymal stem/stromal cells (BMSC) in bone tissue engineering and regenerative medicine-based applications. The multipotent differentiation potential, myelosupportive capacity, anti-inflammatory and immune-modulatory properties of BMSC underpins their versatile nature as therapeutic agents. This review addresses the current limitations and challenges of exogenous autologous and allogeneic BMSC based regenerative skeletal therapies in combination with bioactive molecules, cellular derivatives, genetic manipulation, biocompatible hydrogels, solid and composite scaffolds. The review highlights the current approaches and recent developments in utilizing endogenous BMSC activation or exogenous BMSC for the repair of long bone and vertebrae fractures due to osteoporosis or trauma. Current advances employing BMSC based therapies for bone regeneration of craniofacial defects is also discussed. Moreover, this review discusses the latest developments utilizing BMSC therapies in the preclinical and clinical settings, including the treatment of bone related diseases such as Osteogenesis Imperfecta.

Matrix Control of Periodontal Ligament Cell Activity Via Synthetic Hydrogel Scaffolds

Rebuilding the tooth-supporting tissues (periodontium) destroyed by periodontitis remains a clinical challenge. Periodontal ligament cells (PDLCs), multipotent cells within the periodontal ligament (PDL), differentiate and form new PDL and mineralized tissues (cementum and bone) during native tissue repair in response to specific extracellular matrix (ECM) cues. Thus, harnessing ECM cues to control PDLC activity ex vivo, and ultimately, to design a PDLC delivery vehicle for tissue regeneration is an important goal. In this study, poly(ethylene glycol) hydrogels were used as a synthetic PDL ECM to interrogate the roles of cell-matrix interactions and cell-mediated matrix remodeling in controlling PDLC activity. Results showed that PDLCs within matrix metalloproteinase (MMP)-degradable hydrogels expressed key PDL matrix genes and showed a six to eightfold increase in alkaline phosphatase (ALP) activity compared with PDLCs in nondegradable hydrogel controls. The increase in ALP activity, commonly considered an early marker of cementogenic/osteogenic differentiation, occurred independent of the presentation of the cell-binding ligand RGD or soluble media cues and remained elevated when inhibiting PDLC-matrix binding and intracellular tension. ALP activity was further increased in softer hydrogels regardless of degradability and was accompanied by an increase in PDLC volume. However, scaffolds that fostered PDLC ALP activity did not necessarily promote hydrogel ECM mineralization. Rather, matrix mineralization was greatest in stiffer, MMP-degradable hydrogels and required the presence of soluble media cues. These divergent outcomes illustrate the complexity of the PDLC response to ECM cues and the limitations of current scaffold materials. Nevertheless, key biomaterial design principles for controlling PDLC activity were identified for incorporation into scaffolds for periodontal tissue regeneration. Impact statement Engineered scaffolds are an attractive approach for delivering periodontal ligament cells (PDLCs) to rebuild the tooth-supporting tissues. Replicating key extracellular matrix (ECM) cues within tissue engineered scaffolds may maximize PDLC potential. However, the identity of important ECM cues and how they can be harnessed to control PDLC activity is still unknown. In this study, matrix degradability, cell-matrix binding, and stiffness were varied using synthetic poly(ethylene glycol) hydrogels for three-dimensional PDLC culture. PDLCs exhibited dramatic and divergent responses to these cues, supporting further investigation of ECM-replicating scaffolds for control of PDLC behavior and periodontal tissue regeneration.

Tooth-Supporting Hard Tissue Regeneration Using Biopolymeric Material Fabrication Strategies

The mineralized tissues (alveolar bone and cementum) are the major components of periodontal tissues and play a critical role to anchor periodontal ligament (PDL) to tooth-root surfaces. The integrated multiple tissues could generate biological or physiological responses to transmitted biomechanical forces by mastication or occlusion. However, due to periodontitis or traumatic injuries, affect destruction or progressive damage of periodontal hard tissues including PDL could be affected and consequently lead to tooth loss. Conventional tissue engineering approaches have been developed to regenerate or repair periodontium but, engineered periodontal tissue formation is still challenging because there are still limitations to control spatial compartmentalization for individual tissues and provide optimal 3D constructs for tooth-supporting tissue regeneration and maturation. Here, we present the recently developed strategies to induce osteogenesis and cementogenesis by the fabrication of 3D architectures or the chemical modifications of biopolymeric materials. These techniques in tooth-supporting hard tissue engineering are highly promising to promote the periodontal regeneration and advance the interfacial tissue formation for tissue integrations of PDL fibrous connective tissue bundles (alveolar bone-to-PDL or PDL-to-cementum) for functioning restorations of the periodontal complex.

Stem cell therapies for periodontal tissue regeneration: a network meta-analysis of preclinical studies

Background

Periodontal tissue regeneration (PTR) is the ultimate goal of periodontal therapy. Currently, stem cell therapy is considered a promising strategy for achieving PTR. However, there is still no conclusive comparison that distinguishes clear hierarchies among different kinds of stem cells.

Methods

A systematic review and network meta-analysis (NMA) was performed using MEDLINE (via PubMed), EMBASE, and Web of Science up to February 2020. Preclinical studies assessing five types of stem cells for PTR were included; the five types of stem cells included periodontal ligament-derived stem cells (PDLSCs), bone marrow-derived stem cells (BMSCs), adipose tissue-derived stem cells (ADSCs), dental pulp-derived stem cells (DPSCs), and gingival-derived stem cells (GMSCs). The primary outcomes were three histological indicators with continuous variables: newly formed alveolar bone (NB), newly formed cementum (NC), and newly formed periodontal ligament (NPDL). We performed pairwise meta-analyses using a random-effects model and then performed a random-effects NMA using a multivariate meta-analysis model.

Results

Sixty preclinical studies assessing five different stem cell-based therapies were identified. The NMA showed that in terms of NB, PDLSCs (standardized mean difference 1.87, 95% credible interval 1.24 to 2.51), BMSCs (1.88, 1.17 to 2.59), and DPSCs (1.69, 0.64 to 2.75) were statistically more efficacious than cell carriers (CCs). In addition, PDLSCs were superior to GMSCs (1.49, 0.04 to 2.94). For NC, PDLSCs (2.18, 1.48 to 2.87), BMSCs (2.11, 1.28 to 2.94), and ADSCs (1.55, 0.18 to 2.91) were superior to CCs. For NPDL, PDLSCs (1.69, 0.92 to 2.47) and BMSCs (1.41, 0.56 to 2.26) were more efficacious than CCs, and PDLSCs (1.26, 0.11 to 2.42) were superior to GMSCs. The results of treatment hierarchies also demonstrated that the two highest-ranked interventions were PDLSCs and BMSCs.

Conclusion

PDLSCs and BMSCs were the most effective and well-documented stem cells for PTR among the five kinds of stem cells evaluated in this study, and there was no statistical significance between them. To translate the stem cell therapies for PTR successfully in the clinic, future studies should utilize robust experimental designs and reports.

[Functions of non-coding RNAs in the osteogenic differentiation of human periodontal ligament-derived cells]

Human periodontal ligament-derived cells serve as an important source of seeding cells in periodontal regenerative medicine, and their osteogenic potential is closely related to alveolar bone repair and periodontal regeneration. Non-coding RNA (ncRNA), such as microRNA, long non-coding RNA, and circular RNA, play important roles in the regu-lation of osteogenic genes in human periodontal ligament-derived cells. In this review, we summarize the target genes, path-ways, and functions of the ncRNA network during osteogenic differentiation of periodontal ligament-derived cells.

Low-intensity pulsed ultrasound activates autophagy in periodontal ligament cells in the presence or absence of lipopolysaccharide

OBJECTIVE

This study aims to determine if low-intensity pulsed ultrasound (LIPUS) activates autophagy in human periodontal ligament cells (PDLCs) irrespective of lipopolysaccharide.

DESIGN

Six groups were designed: control, LIPUS, lipopolysaccharide, LIPUS + lipopolysaccharide, LIPUS+3-Methyladenine, LIPUS + lipopolysaccharide+3-Methyl- adenine. LIPUS pretreated PDLCs for 2 h and lipopolysaccharide treated for different times. Real-time PCR and Western-blot were performed to evaluate mRNA and protein expression levels of autophagic genes Beclin-1 and LC3 respectively. A transmission electronic microscope was used to observe the autophagosome. ELISA was used to test interleukin-6 expression.

RESULTS

Compared with the non-treatment, LIPUS pretreatment increased mRNA expression levels of LC3 (P < 0.05) and Beclin-1 (P < 0.05) at 4 h and 8 h, and enhanced the protein expression levels of LC3-Ⅱ at 8 h (P<0.05) and Beclin-1 at 4 h, 8 h and 16 h(P<0.05). After LIPUS pretreatment and lipopolysaccharide treatment for 8 h, LC3-Ⅱ and Beclin-1 protein expression levels were elevated (P < 0.05) compared with the control. Following further treatment by 3-Methyladenine, Beclin-1 protein expression was decreased (P < 0.05) compared with the LIPUS plus lipopolysaccharide group, but LC3-Ⅱ protein expression was not. Autophagosomes were not found in the LIPUS+3-Methyladenine and LIPUS+lipopolysaccharide+3-Methyladenine groups. After LIPUS pretreatment and lipopolysaccharide treatment for 36 h, intreleukin-6 expression was decreased (P<0.05) compared with the lipopolysaccharide group. However, after addition of 3-Methyladenine, intreleukin-6 expression was elevated (P < 0.05) compared with the LIPUS +lipopolysaccharide group.

CONCLUSIONS

LIPUS can promote autophagy in PDLCs irrespective of lipopolysaccharide. Autophagy might be involved in LIPUS anti-inflammatory mechanism in PDLCS.

Promising advances in clinical trials of dental tissue-derived cell-based regenerative medicine

Background

Advances in regenerative medicine with stem cells have led to clinical trials. Dental/oral tissues are emerging as promising cellular sources of human mesenchymal stem cells. Recently, dental tissue-derived cells have been used clinically due to their great potential, easy accessibility, and ability to be obtained via methods with low invasiveness. The aim of this study is to systematically assess the clinical effectiveness of dental cell-mediated therapies compared to current evidence-based methods in human patients.

Methods

The electronic databases MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov were searched up to December 2019 for clinical trials. Clinical trials with any intervention using stem cells/cells derived from dental tissue were included.

Results

A total of 815 studies were identified by the electronic search, and 38 articles qualified for full-text evaluation. Finally, 20 studies (10 clinical trials using dental pulp-derived cells, 3 clinical trials using periodontal ligament-derived cells, and 7 studies using gingiva-derived cells) were included in this review. No clinical trials using dental follicle- or apical papilla-derived cells were selected in this review. Dental pulp-derived cells were used in clinical trials for bone regeneration, periodontitis, and dental pulp regeneration. All clinical trials using periodontal ligament-derived cells and gingiva-derived cells were conducted for periodontal disease treatment and gingival augmentation, respectively. Among the 20 selected studies, 16 showed clinical benefits of cell transplantation therapies. In addition, no study reported adverse events that may have been associated with cell transplantation.

Conclusions

These findings indicate that dental tissue-derived cells would be useful for cell-based regenerative medicine for various diseases.

Transcriptional Expression in Human Periodontal Ligament Cells Subjected to Orthodontic Force: An RNA-Sequencing Study

This study was performed to investigate the changes in gene expression in periodontal ligament (PDL) cells following mechanical stimulus through RNA sequencing. In this study, premolars extracted for orthodontic treatment were used. To stimulate the PDL cells, an orthodontic force of 100× g was applied to the premolar (experimental group; n = 11), whereas the tooth on the other side was left untreated (control group; n = 11). After the PDL cells were isolated from the extracted teeth, gene set enrichment analysis (GSEA), differentially expressed gene (DEG) analysis, and real-time PCR were performed to compare the two groups. GSEA demonstrated that gene sets related to the cell cycle pathway were upregulated in PDL. Thirteen upregulated and twenty downregulated genes were found through DEG analysis. Real-time PCR results confirmed that five upregulated genes (CC2D1B, CPNE3, OPHN1, TANGO2, and UAP-1) and six downregulated genes (MYOM2, PPM1F, PCDP1, ATP2A1, GPR171, and RP1-34H18.1-1) were consistent with RNA sequencing results. We suggest that, from among these eleven genes, two upregulated genes, CPNE3 and OPHN1, and one downregulated gene, PPM1F, play an important role in PDL regeneration in humans when orthodontic force is applied.

EphrinB2 regulates osteogenic differentiation of periodontal ligament stem cells and alveolar bone defect regeneration in beagles

EphrinB2, a membrane protein regulating bone homeostasis, has been demonstrated to induce osteogenic gene expression in periodontal ligament fibroblasts. The aim of this study was to explore the effects of ephrinB2 on osteogenic differentiation of periodontal ligament stem cells and on alveolar bone regeneration in vivo. We assessed the osteogenic gene expression and osteogenic differentiation potential of ephrinB2-modified human and canine periodontal ligament stem cells, in which ephrinB2 expression was upregulated via lentiviral vector transduction. EphrinB2-modified canine periodontal ligament stem cells combined with PuraMatrix were delivered to critical-sized alveolar bone defects in beagles to evaluate bone regeneration. Results showed that ephrinB2 overexpression enhanced osteogenic gene transcription and mineral deposition in both human and canine periodontal ligament stem cells. Animal experiments confirmed that ephrinB2-modified canine periodontal ligament stem cells + PuraMatrix resulted in greater trabecular bone volume per tissue volume and trabecular thickness compared with other groups. Our study demonstrated that ephrinB2 promoted osteogenic differentiation of periodontal ligament stem cells and alveolar bone repair in beagles, highlighting its therapeutic potential for the treatment of alveolar bone damage.

Macrophage polarization in periodontal ligament stem cells enhanced periodontal regeneration

Background

The inflammation and regeneration process may be accompanied by the shift in the M1/M2 polarization of macrophages to adapt to extracellular signals. How the macrophages responded to the altered immunological environment in the periodontal niche after stem cell transplantation has never been explored. The purpose of present study is to investigate whether M1/M2 polarization of macrophages participated in the tissue homeostasis and wound healing during periodontal ligament stem cell (PDLSC)-based periodontal regeneration.

Methods

A rat periodontal defect model was utilized to observe the regeneration process in the PDLSC transplantation-enhanced periodontal repair. Dynamic changes in the markers of M1/M2 macrophages were observed on days 3, 7, and 21 post surgery. In addition, the outcome of regeneration was analyzed on day 21 after surgery. To further investigate the effect of PDLSCs on macrophage polarization, the conditioned medium of PDLSCs was utilized to treat M0, M1, and M2 macrophages for 24 h; markers of M1/M2 polarization were evaluated in macrophages.

Results

Elevated bone volume and average thickness of bone trabecular was observed in the PDLSC-treated group by micro-computed tomography on day 21. In addition, enhanced periodontal regeneration was observed in the PDLSC-treated group with cementum-like structure regeneration and collagen fiber formation, which inserted into the newly formed cementum. On day 3, PDLSC transplantation increased IL-10 level in the periodontal tissue, while decreased TNF-α in the early stage of periodontal regeneration. On day 7, enhanced CD163+ cell infiltration and heightened expression of markers of M2 macrophages were observed. Furthermore, conditioned medium from PDLSC culture induced macrophage polarization towards the anti-inflammatory phenotype by downregulating TNF-α and upregulating IL-10, Arg-1, and CD163 in vitro.

Conclusions

PDLSCs could induce macrophage polarization towards the M2 phenotype, and the shift in the polarization towards M2 macrophages in the early stage of tissue repair contributed to the enhanced periodontal regeneration after stem cell transplantation. Therefore, signals from the transplanted PDLSCs might alter the immune microenvironment to enhance periodontal regeneration.