Therapeutic potential of periodontal ligament stem cells

Inflammatory periodontal disease known as periodontitis is one of the most common conditions that affect human teeth and often leads to tooth loss.Due to the complexity of the periodontium,which is composed of several tissues,its regeneration and subsequent return to a homeostatic state is challenging with the therapies currently available.Cellular therapy is increasingly becoming an alternative in regenerative medicine/dentistry,especially therapies using mesenchymal stem cells,as they can be isolated from a myriad of tissues.Periodontal ligament stem cells(PDLSCs)are probably the most adequate to be used as a cell source with the aim of regenerating the periodontium.Biological insights have also highlighted PDLSCs as promising immunomodulator agents.In this review,we explore the state of knowledge regarding the properties of PDLSCs,as well as their therapeutic potential,describing current and future clinical applications based on tissue engineering techniques.

Exosomes Derived from Human Umbilical Cord Mesenchymal Stem Cells Enhance the Osteoblastic Differentiation of Periodontal Ligament Stem Cells Under High Glucose Conditions Through the PI3K/AKT Signaling Pathway

Objective High glucose(HG)can influence the osteogenic differentiation ability of periodontal ligament stem cells(PDLSCs).Human umbilical cord mesenchymal stem cell-derived exosomes(hUCMSC-exo)have broad application prospects in tissue healing.The current study aimed to explore whether hUCMSC-exo could promote the osteogenic differentiation of hPDLSCs under HG conditions and the underlying mechanism.Methods We used a 30 mmol/L glucose concentration to simulate HG conditions.CCK-8 assay was performed to evaluate the effect of hUCMSC-exo on the proliferation of hPDLSCs.Alkaline phosphatase(ALP)staining,ALP activity,and qRT-PCR were performed to evaluate the pro-osteogenic effect of hUCMSC-exo on hPDLSCs.Western blot analysis was conducted to evaluate the underlying mechanism.Results The results of the CCK-8 assay,ALP staining,ALP activity,and qRT-PCR assay showed that hUCMSC-exo significantly promoted cell proliferation and osteogenic differentiation in a dosedependent manner.The Western blot results revealed that hUCMSC-exo significantly increased the levels of p-PI3K and p-AKT in cells,and the effect was inhibited by LY294002(PI3K inhibitor)or MK2206(AKT inhibitor),respectively.Moreover,the increases in osteogenic indicators induced by hUCMSC-exo were significantly suppressed by LY294002 and MK2206.Conclusion hUCMSC-exo promote the osteogenic differentiation of hPDLSCs under HG conditions through the PI3K/AKT signaling pathway.

Mass acquisition of human periodontal ligament stem cells

The periodontal ligament(PDL)is an essential fibrous tissue for tooth retention in the alveolar bone socket.PDL tissue further functions to cushion occlusal force,maintain alveolar bone height,allow orthodontic tooth movement,and connect tooth roots with bone.Severe periodontitis,deep caries,and trauma cause irreversible damage to this tissue,eventually leading to tooth loss through the destruction of tooth retention.Many patients suffer from these diseases worldwide,and its prevalence increases with age.To address this issue,regenerative medicine for damaged PDL tissue as well as the surrounding tissues has been extensively investigated regarding the potential and effectiveness of stem cells,scaffolds,and cytokines as well as their combined applications.In particular,PDL stem cells(PDLSCs)have been well studied.In this review,I discuss comprehensive studies on PDLSCs performed in vivo and contemporary reports focusing on the acquisition of large numbers of PDLSCs for therapeutic applications because of the very small number of PDLSCs available in vivo.

Human periodontal ligament stem cells repair mental nerve injury

Human periodontal ligament stem cells are easily accessible and can differentiate into Schwann cells. We hypothesized that human periodontal ligament stem cells can be used as an alternative source for the autologous Schwann cells in promoting the regeneration of injured peripheral nerve. To validate this hypothesis, human periodontal ligament stem cells （1 × 106） were injected into the crush-injured left mental nerve in rats. Simultaneously, autologous Schwann cells （1 × 106） and PBS were also injected as controls. Real-time reverse transcriptase polymerase chain reaction showed that at 5 days after injection, mRNA expression of low affinity nerve growth factor receptor was sig-nificantaly increased in the left trigeminal ganglion of rats with mental nerve injury. Sensory tests, histomorphometric evaluation and retrograde labeling demonstrated that at 2 and 4 weeks after in-jection, sensory function was significantly improved, the numbers of retrograde labeled sensory neurons and myelinated axons were significantly increased, and human periodontal ligament stem cells and autologous Schwann cells exhibited similar therapeutic effects. These findings suggest that transplantation of human periodontal ligament stem cells show a potential value in repair of mental nerve injury.

Overview of the main biological mechanisms linked to changes in periodontal ligament stem cells and the inflammatory microenvironment

Periodontitis is a complex chronic inflammatory disease.The invasion of pathogens induces the inflammatory microenvironment in periodontitis.Cell behavior changes in response to changes in the microenvironment,which in turn alters the local inflammatory microenvironment of the periodontium through factors secreted by cells.It has been confirmed that periodontal ligament stem cells(PDLSCs)are vital in the development of periodontal disease.Moreover,PDLSCs are the most effective cell type to be used for periodontium regeneration.This review focuses on changes in PDLSCs,their basic biological behavior,osteogenic differentiation,and drug effects caused by the inflammatory microenvironment,to provide a better understanding of the influence of these factors on periodontal tissue homeostasis.In addition,we discuss the underlying mechanism in detail behind the reciprocal responses of PDLSCs that affect the microenvironment.

Effects of Ginsenoside Rg-1 on the Proliferation and Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

Objective： TO evaluate the effects of ginsenoside Rg-1 on the proliferation and osteogenic differentiation of human periodontal ligament stem cells （hPDLSCs） and to explore the possible application on the alveolar bone regeneration. Methods： To determine the optimum concentration, the effects of ginsenoside Rg-1 ranging from 10 to 100 μmol/L were evaluated by 3-（4,5）-dimethylthiahiazo（-z-yl）-3,5-di-phenytetrazoliumromide, alkaline phosphatase activity and calcium deposition. Expressions of runt-related transcription factor 2, collagen alpha-2（I） chain, osteopontin, osteocalcin protein were examined using real-time polymerase chain reaction. Results： Compared with the control group, a certain concentration （10 μmol/L） of the Rg-1 solution significantly enhanced the proliferation and osteogenic differentiation of hPDLSCs （P〈0.05）. However, concentrations that exceeds 100 μmol/L led to cytotoxicity whereas concentrations below 10 nmol/L showed no significant effect as compared with the control. Conclusion： Ginsenoside Rg-1 can enhance the proliferation and osteogenic differentiation of hPDLSCs at an optimal concentration of 10 μmol/L.

Effects of Aging on the Proliferation and Differentiation Capacity of Human Periodontal Ligament Stem Cells

periodontal ligament stem cells; aging; proliferation; osteogenic differentiation Objective The aim of this study is to investigate the proliferation, differentiation and apoptosis of periodontal ligament stem cells （PDLSC） derived from different aged donors, and to evaluate the effects of aging on the biological characteristics of PDLSC. Methods Periodontal ligament tissues were obtained from 24 surgically extracted human premolars during orthodontics therapy. The specimens were divided into three groups according to the donor’s age. Group A： 18-20 years, group B： 30-35 years, group C： 45-50 years. PDLSC were isolated and cultured using a tissue-block-based enzymolytic method by limiting dilution assay. The colony forming efficiency of PDLSC for three experimental groups was determined. Senescence-Associated β-Galactosidase （SA-β-G） expression in the three groups was examined using β-galactosidase staining working solution. Cell cycle and apoptosis of the PDLSC were examined by the flow cytometry. Alkaline phosphatase （ALP） activity was evaluated by ALP staining. The expression of osteoplastic differentiation related genes Runt-related transcription factor-2 （Runx-2）, Collagen Type 1 （col-1）, and ALP of PDLSC were examined by quantitative real-time RT-PCR. Results The colony forming efficiency of PDLSC in Group A, B and C was 36.67%, 22.67% and 9.33%, respectively, which decreased with donors’ age （P〈0.05）. SA-β-G expression of the senescent PDLSC in group A, B and C were 4.14%, 16.39%, 50.38%, respectively （P〈0.05）. Cells in G2/S phase was 38.73%, 29.88%, 18.25% （P〈0.05）, and the apoptosis rate was 1.57%, 4.56%, 5.84% （P〈0.05）, in group A, B and C respectively. The ALP staining in the three groups decreased with the increase of donors’ ages, and the expression of Runx-2, col-1 and ALP decreased gradually from group A to group C （all P〈0.05）, which indicated the osteogenic differentiation capacity of PDLSC decreased while donor aging. Conclusion Human PDLSC could be successfully isolated from periodontal ligament tissues of different aged donors. However, the proliferation and osteogenic differentiation capacity of PDLSC decreased while donor aging.

Proteomic profiling of various human dental stem cells-a systematic review

BACKGROUND The proteomic signature or profile best describes the functional component of a cell during its routine metabolic and survival activities.Additional complexity in differentiation and maturation is observed in stem/progenitor cells.The role of functional proteins at the cellular level has long been attributed to anatomical niches,and stem cells do not deflect from this attribution.Human dental stem cells(hDSCs),on the whole,are a combination of mesenchymal and epithelial coordinates observed throughout craniofacial bones to pulp.AIM To specify the proteomic profile and compare each type of hDSC with other mesenchymal stem cells(MSCs)of various niches.Furthermore,we analyzed the characteristics of the microenvironment and preconditioning changes associated with the proteomic profile of hDSCs and their influence on committed lineage differentiation.METHODS Literature searches were performed in PubMed,EMBASE,Scopus,and Web of Science databases,from January 1990 to December 2018.An extra inquiry of the grey literature was completed on Google Scholar,ProQuest,and OpenGrey.Relevant MeSH terms(PubMed)and keywords related to dental stem cells were used independently and in combination.RESULTS The initial search resulted in 134 articles.Of the 134 full-texts assessed,96 articles were excluded and 38 articles that met the eligibility criteria were reviewed.The overall assessment of hDSCs and other MSCs suggests that differences in the proteomic profile can be due to stem cellular complexity acquired from varied tissue sources during embryonic development.However,our comparison of the proteomic profile suffered inconsistencies due to the heterogeneity of various hDSCs.We believe that the existence of a heterogeneous population of stem cells at a given niche determines the modalities of regeneration or tissue repair.Added prominences to the differences present between various hDSCs have been reasoned out.CONCLUSION Systematic review on proteomic studies of various hDSCs are promising as an eye-opener for revisiting the proteomic profile and in-depth analysis to elucidate more refined mechanisms of hDSC functionalities.

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

AIM： To explore the possibility of human umbilical cord mesenchymal stem cells（h UCMSCs）, human umbilical vein endothelial cells（h UVECs）, human dental pulp stem cells（h DPSCs） and human periodontal ligament stem cells（h PDLSCs） serving as feeder cells in co-culture systems for the cultivation of limbal stem cells.METHODS： Different feeder layers were cultured in Dulbecco＇s modified Eagle＇s medium（DMEM）/F12 and were treated with mitomycin C. Rabbits limbal stem cells（LSCs） were co-cultured on h UCMSCs, h UVECs, h DPSCs, h PDLSCs and NIH-3T3, and then comparative analysis were made between each group to see their respective colony-forming efficiency（CFE） assay and immunofluorescence（IPO13,CK3/12）.RESULTS： The efficiency of the four type cells in supporting the LSCs morphology and its cellular differentiation was similar to that of NIH-3T3 fibroblasts as demonstrated by the immunostaining properties analysis, with each group exhibiting a similar strong expression pattern of IPO13, but lacking CK3 and CK12 expression in terms of immunostaining. But h UCMSCs, h DPSCs and h PDLSCs feeder layers were superior in promoting colony formation potential of cells when compared to h UVECs and feedercell-free culture.CONCLUSION： hUCMSCs, hDPSCs and hPDLSCs can be a suitable alternative to conventional mouse NIH-3T3 feeder cells, so that risk of zoonotic infection can be diminished.

Application of dental stem cells in three-dimensional tissue regeneration

Dental stem cells can differentiate into different types of cells.Dental pulp stem cells,stem cells from human exfoliated deciduous teeth,periodontal ligament stem cells,stem cells from apical papilla,and dental follicle progenitor cells are five different types of dental stem cells that have been identified during different stages of tooth development.The availability of dental stem cells from discarded or removed teeth makes them promising candidates for tissue engineering.In recent years,three-dimensional(3D)tissue scaffolds have been used to reconstruct and restore different anatomical defects.With rapid advances in 3D tissue engineering,dental stem cells have been used in the regeneration of 3D engineered tissue.This review presents an overview of different types of dental stem cells used in 3D tissue regeneration,which are currently the most common type of stem cells used to treat human tissue conditions.

Research progress of strontium in promoting periodontal tissue regeneration

Periodontal disease is a chronic infectious disease of the oral cavity.Its main clinical features are periodontal pocket formation and alveolar bone resorption.Scholars'research hotspot is to achieve periodontal tissue regeneration in patients.Studies have found that strontium has certain potential in promoting periodontal tissue regeneration.In recent years,scholars have been conducting research on strontium and periodontal tissue regeneration,with a view to opening a new path for periodontal disease treatment.This article reviews the research status of strontium and periodontal tissue regeneration.The review results show that strontium can induce the proliferation and differentiation of PDLSCs and promote the regeneration of lost bone tissue;it can inhibit osteoclast activity and induce osteoclast apoptosis through a variety of signaling pathways,thereby inhibiting bone resorption;Promote bone formation;Strontium also has the function of promoting early angiogenesis and suppressing immune inflammatory response.Because the current research on strontium and periodontal tissue regeneration is only focused on in vivo and in vitro experiments,there is no relevant clinical trial to apply strontium to periodontal tissue regeneration.Therefore,if strontium is used to promote periodontal tissue regeneration to achieve the treatment of periodontal disease,further research is needed.

Oral stem cells,decoding and mapping the resident cells populations

The teeth and their supporting tissues provide an easily accessible source of oral stem cells.These different stem cell populations have been extensively studied for their properties,such as high plasticity and clonogenicity,expressing stem cell markers and potency for multilineage differentiation in vitro.Such cells with stem cell properties have been derived and characterised from the dental pulp tissue,the apical papilla region of roots in development,as well as the supporting tissue of periodontal ligament that anchors the tooth within the alveolar socket and the soft gingival tissue.Studying the dental pulp stem cell populations in a continuously growing mouse incisor model,as a traceable in vivo model,enables the researchers to study the properties,origin and behaviour of mesenchymal stem cells.On the other side,the oral mucosa with its remarkable scarless wound healing phenotype,offers a model to study a well-coordinated system of healing because of coordinated actions between epithelial,mesenchymal and immune cells populations.Although described as homogeneous cell populations following their in vitro expansion,the increasing application of approaches that allow tracing of individual cells over time,along with single-cell RNA-sequencing,reveal that different oral stem cells are indeed diverse populations and there is a highly organised map of cell populations according to their location in resident tissues,elucidating diverse stem cell niches within the oral tissues.This review covers the current knowledge of diverse oral stem cells,focusing on the new approaches in studying these cells.These approaches“decode”and“map”the resident cells populations of diverse oral tissues and contribute to a better understanding of the“stem cells niche architecture and interactions.Considering the high accessibility and simplicity in obtaining these diverse stem cells,the new findings offer potential in development of translational tissue engineering approaches and innovative therapeutic solutions.

Cerium oxide nanoparticles loaded nanofibrous membranes promote bone regeneration for periodontal tissue engineering

Bone regeneration is a crucial part in the treatment of periodontal tissue regeneration,in which new attempts come out along with the development of nanomaterials.Herein,the effect of cerium oxide nanoparticles(CeO_(2)NPs)on the cell behavior and function of human periodontal ligament stem cells(hPDLSCs)was investigated.Results of CCK-8 and cell cycle tests demonstrated that CeO_(2)NPs not only had good biocompatibility,but also promoted cell proliferation.Furthermore,the levels of alkaline phosphatase activity,mineralized nodule formation and expressions of osteogenic genes and proteins demonstrated CeO_(2)NPs could promote osteogenesis differentiation of hPDLSCs.Then we chose electrospinning to fabricate fibrous membranes containing CeO_(2)NPs.We showed that the composite membranes improved mechanical properties as well as realized release of CeO_(2)NPs.We then applied the composite membranes to in vivo study in rat cranial defect models.Micro-CT and histopathological evaluations revealed that nanofibrous membranes with CeO_(2)NPs further accelerated new bone formation.Those exciting results demonstrated that CeO_(2)NPs and porous membrane contributed to osteogenic ability,and CeO_(2)NPs contained electrospun membrane may be a promising candidate material for periodontal bone regeneration.