Long noncoding RNA related to periodontitis interacts with miR-182 to upregulate osteogenic differentiation in periodontal mesenchymal stem cells of periodontitis patients. Cell Death Dis. 2016;7:e2327. [PMID: 27512949 PMCID: PMC5108307 DOI: 10.1038/cddis.2016.125]

The Effects of Different Developmental Stages on Bone Regeneration of Periodontal Ligament Stem Cells and Periodontal Ligament Cell Sheets In Vitro and Vivo

Periodontal ligament stem cells (PDLSCs) have broad applications in tissue engineering and regeneration. However, the function of PDLSCs changes in different microenvironments. This study aimed to explore the effects of different developmental stages on the biological characteristics of PDLSCs. Here, PDLSCs were successfully cultured from the periodontal tissues of various groups, including a group with immature roots, a young group with mature roots, and an aging group with mature roots. By comparing the results of the three experimental groups, we found that the donors with immature roots exhibited the best proliferative ability and osteogenic differentiation, while the aging group demonstrated the worst proliferation. The trend for adipogenic differentiation was the opposite to that for osteogenic differentiation. The cell sheet and in vivo experiments revealed that in the immature root group, the cells produced more extracellular matrix (ECM) and new bone and better absorbed the implant materials. These results indicate that PDLSCs perform various functions at different stages of development. In clinical applications of PDLSCs for periodontal regeneration, donors with incompletely developed roots have stronger biological characteristics.

Regulation of bone homeostasis: signaling pathways and therapeutic targets

As a highly dynamic tissue, bone is continuously rebuilt throughout life. Both bone formation by osteoblasts and bone resorption by osteoclasts constitute bone reconstruction homeostasis. The equilibrium of bone homeostasis is governed by many complicated signaling pathways that weave together to form an intricate network. These pathways coordinate the meticulous processes of bone formation and resorption, ensuring the structural integrity and dynamic vitality of the skeletal system. Dysregulation of the bone homeostatic regulatory signaling network contributes to the development and progression of many skeletal diseases. Significantly, imbalanced bone homeostasis further disrupts the signaling network and triggers a cascade reaction that exacerbates disease progression and engenders a deleterious cycle. Here, we summarize the influence of signaling pathways on bone homeostasis, elucidating the interplay and crosstalk among them. Additionally, we review the mechanisms underpinning bone homeostatic imbalances across diverse disease landscapes, highlighting current and prospective therapeutic targets and clinical drugs. We hope that this review will contribute to a holistic understanding of the signaling pathways and molecular mechanisms sustaining bone homeostasis, which are promising to contribute to further research on bone homeostasis and shed light on the development of targeted drugs.

Dental pulp stem cells - A basic research and future application in regenerative medicine

Dental pulp is a valuable and accessible source of stem cells (DPSCs) with characteristics similar to mesenchymal stem cells. DPSCs can regenerate a range of tissues and their potential for clinical application in regenerative medicine is promising. DPSCs have been found to express low levels of Class II HLA-DR (MHC) molecules, making them potential candidates for allogeneic transplantation without matching the donor's tissue. Research on the correlation between non-coding RNAs (ncRNAs) and human dental pulp stem cells (DPSCs) provides promising insights into the use of these cells in clinical settings for a wide range of medical conditions. It is possible to use a number of ncRNAs in order to restore the functional role of downregulated ncRNAs that are correlated with osteoblastogenesis, or to suppress the functional role of overexpressed ncRNAs associated with osteoclast differentiation in some cases.

miR-708-3p targetedly regulates LSD1 to promote osteoblast differentiation of hPDLSCs in periodontitis

Periodontitis (PD) is a multifactorial inflammatory disease associated with periodontopathic bacteria. Lysine-specific demethylase 1 (LSD1), a type of histone demethylase, has been implicated in the modulation of the inflammatory response process in oral diseases by binding to miRNA targets. This study investigates the molecular mechanisms by which miRNA binds to LSD1 and its subsequent effect on osteogenic differentiation. First, human periodontal ligament stem cells (hPDLSCs) were isolated, cultured, and characterized. These cells were then subjected to lipopolysaccharide (LPS) treatment to induce inflammation, after which osteogenic differentiation was initiated. qPCR and western blot were employed to monitor changes in LSD1 expression. Subsequently, LSD1 was silenced in hPDLSCs to evaluate its impact on osteogenic differentiation. Through bioinformatics and dual luciferase reporter assay, miR-708-3p was predicted and confirmed as a target miRNA of LSD1. Subsequently, miR-708-3p expression was assessed, and its role in hPDLSCs in PD was evaluated through overexpression. Using chromatin immunoprecipitation (ChIP) and western blot assay, we explored the potential regulation of osterix (OSX) transcription by miR-708-3p and LSD1 via di-methylated H3K4 (H3K4me2). Finally, we investigated the role of OSX in hPDLSCs. Following LPS treatment of hPDLSCs, the expression of LSD1 increased, but this trend was reversed upon the induction of osteogenic differentiation. Silencing LSD1 strengthened the osteogenic differentiation of hPDLSCs. miR-708-3p was found to directly bind to and negatively regulate LSD1, leading to the repression of OSX transcription through demethylation of H3K4me2. Moreover, overexpression of miR-708-3p was found to promote hPDLSCs osteogenic differentiation in inflammatory microenvironment. However, the protective effect was partially attenuated by reduced expression of OSX. Our findings indicate that miR-708-3p targetedly regulates LSD1 to enhance OSX transcription via H3K4me2 methylation, ultimately promoting hPDLSCs osteogenic differentiation.

Long intergenic non-coding RNA 01126 activates IL-6/JAK2/STAT3 pathway to promote periodontitis pathogenesis

OBJECTIVES

Periodontitis seriously affects oral-related quality of life and overall health. Long intergenic non-coding RNA 01126 (LINC01126) is aberrantly expressed in periodontitis tissues. This study aimed to explore the possible pathogenesis of LINC01126 in periodontitis.

METHODS

Inflammatory model of human gingival fibroblasts (HGFs) was established. Cell Counting Kit-8 (CCK-8), wound healing assay, and flow cytometry were utilized to detect biological roles of LINC01126. Binding site of miR-655-3p to LINC01126 and IL-6 was predicted. Then, subcellular localization of LINC01126 and the binding ability of miR-655-3p to LINC01126 and IL-6 in HGFs were verified. Hematoxylin-Eosin (H&E) staining and immunohistochemistry (IHC) staining were utilized to detect tissue morphology and proteins expression of clinical samples.

RESULTS

LINC01126 silencing can alleviate cell inflammation induced by lipopolysaccharide derived from Porphyromonas gingivalis, reduce cell apoptosis, and promote cell migration. As a "sponge" for miR-655-3p, LINC01126 inhibits its binding to mRNA of IL-6, thereby promoting inflammation progression and JAK2/STAT3 pathway activation. Quantitative real-time PCR, Western Blot, and IHC results of clinical tissue samples further confirmed that miR-655-3p expression was down-regulated and IL-6/JAK2/STAT3 was abnormally activated in periodontitis tissues.

CONCLUSIONS

In summary, serving as an endogenous competitive RNA of miR-655-3p, LINC01126 promotes IL-6/JAK2/STAT3 pathway activation, thereby promoting periodontitis pathogenesis.

mir-182-5p regulates all three phases of inflammation, proliferation, and remodeling during cutaneous wound healing

Wound healing is a highly programmed process, in which any abnormalities result in scar formation. MicroRNAs are potent regulators affecting wound repair and scarification. However, the function of microRNAs in wound healing is not fully understood. Here, we analyzed the expression and function of microRNAs in patients with cutaneous wounds. Cutaneous wound biopsies from patients with either hypertrophic scarring or normal wound repair were collected during inflammation, proliferation, and remodeling phases. Fourteen candidate microRNAs were selected for expression analysis by qRT-PCR. The expression of genes involved in inflammation, angiogenesis, proliferation, and migration were measured using qRT-PCR. Cell cycle and scratch assays were used to explore the proliferation and migration rates. Flow cytometry analysis was employed to examine TGF-β, αSMA and collagen-I expression. Target gene suggestion was performed using Enrichr tool. The results showed that miR-16-5p, miR-152-3p, miR-125b-5p, miR-34c-5p, and miR-182-5p were revealed to be differentially expressed between scarring and non-scarring wounds. Based on the expression patterns obtained, miR-182-5p was selected for functional studies. miR-182-5p induced RELA expression synergistically upon IL-6 induction in keratinocytes and promoted angiogenesis. miR-182-5p prevented keratinocyte migration, while overexpressed TGF-β3 following induction of inflammation. Moreover, miR-182-5p enhanced fibroblast proliferation, migration, differentiation, and collagen-1 expression. FoxO1 and FoxO3 were found to potentially serve as putative gene targets of miR-182-5p. In conclusion, miR-182-5p is differentially expressed between scarring and non-scarring wounds and affect the behavior of cells involved in cutaneous wound healing. Deregulated expression of miR-182-5p adversely affects the proper transition of wound healing phases, resulting in scar formation.

The Expression Patterns of Non-Coding RNAs in Periodontal Disease

During the last few decades there has been a growing interest in understanding the involvement of epigenetics in the pathogenesis and treatment of periodontal disease. Noncoding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), may serve as epigenetic modifiers affecting the expression of genes involved in the pathogenesis of inflammatory and autoimmune diseases. There is increasing evidence supporting the idea that the function of all three types of ncRNAs seems to be interdependent. LncRNAs can act as miRNA decoys, while circRNAs can act as miRNA sponges, leading to the re-expression of miRNA target genes. The purpose of this review is to evaluate the expression patterns of ncRNAs in periodontal disease. Studies demonstrate a positive correlation between miRNA expression and periodontitis; however, this cannot be claimed for lncRNAs and circRNAs, which appear to be differentially expressed in periodontitis patients. Several studies have also suggested utilizing ncRNAs as diagnostic and prognostic biomarkers in periodontitis, or even as potential therapeutic targets; Nevetheless, the evidence to support this is premature. Future well-designed research remains necessary to establish the functional role of ncRNAs in the evolution and progression of periodontal disease.

LncRNA in periodontal tissue-derived cells on osteogenic differentiation in the periodontitis field

OBJECTIVE

Periodontitis can lead to the destruction of periodontal tissues and potentially tooth loss. Numerous periodontal tissue-derived cells display osteogenic differentiation potential. The presence of differentially expressed long non-coding RNAs (lncRNAs) in these cells indicate their ability to regulate the process of osteogenic differentiation. We aim to elucidate the various lncRNA-mediated regulatory mechanisms in the osteogenic differentiation of periodontal tissue-derived cells in the field of periodontitis at epigenetic modification, transcriptional, and post-transcriptional levels.

SUBJECTS AND METHODS

We systematically searched the PubMed, Web of Science, and ScienceDirect databases to identify relevant literature in the field of periodontitis discussing the role of lncRNAs in regulating osteogenic differentiation of periodontal tissue-derived cells. The identified literature was subsequently summarized for comprehensive review.

RESULTS

In this review, we have comprehensively summarized the regulatory mechanisms of lncRNAs in the osteogenic differentiation of periodontal tissue-derived cells in the field of periodontitis and discussed how these lncRNAs provide novel perspectives for understanding the pathogenesis and progression of periodontitis.

CONCLUSION

These results indicate the pivotal role of lncRNAs as regulators in the osteogenic differentiation of periodontal tissue-derived cells, providing a solid basis for future investigations on the role of lncRNAs in the periodontitis field.

N6-methyladenosine promotes osteogenic differentiation of PDLSCs from periodontitis patients

OBJECTIVES

This study aimed to investigate the mechanism of N6-methyladenosine (m6A) in the osteogenic differentiation of periodontal ligament stem cells (PDLSCs) from periodontitis patients.

METHODS

Differentially m6A-methylated lncRNA/mRNA profiles were detected by a m6A epitranscriptomic microarray. Bioinformatics analysis was performed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis. The transfection efficiency of the lentivirus was detected. The osteogenic activity of PDLSCs from periodontitis patients (PPDLSCs) was assessed.

RESULTS

The microarray results showed that 275 lncRNAs and 1292 mRNAs were significantly differentially methylated between PPDLSCs and PDLSCs from healthy people. Among those lncRNAs, lncRNA4114 (transcript_ID: ENST00000444114) showed both reduced m6A methylation levels and expression levels in PPDLSCs. Further bioinformatics analysis predicted that the differentially methylated mRNAs were mainly involved in cell interaction, stem cell pluripotency, and osteogenic differentiation signals. Then, overexpression of methyltransferase like 3 (METTL3) promoted the osteogenic differentiation of PPDLSCs, while knocking down METTL3 showed an inhibitory effect. Furthermore, METTL3 overexpression promotes the stability of lncRNA4114 to upregulate the expression level. Moreover, lncRNA4114 overexpression promoted the osteogenic differentiation of PPDLSCs.

CONCLUSION

METTL3 promotes the osteogenic differentiation of PPDLSCs by regulating the stability of lncRNA4114.

Identifying genes for regulating osteogenic differentiation of human periodontal ligament stem cells in inflammatory environments by bioinformatics analysis

BACKGROUND AND OBJECTIVES

Periodontitis is an immuno-inflammatory disease caused by dental plaque biofilms and inflammations. The regeneration of bone tissue in inflammatory environment is of great significance for the treatment of periodontal disease, but the specific molecular mechanism of bone formation in periodontitis still needs further exploration. The objective of this study was to identify key osteogenesis-related genes (ORGs) in periodontitis.

METHODS

We used two datasets from the Gene Expression Omnibus (GEO) database to find differentially expressed mRNAs and miRNAs, further performed Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Then we predicted the downstream genes of the differentially expressed miRNAs (DEMs) by the TargetScan database and established a miRNA-mRNA regulatory network. Finally, the osteogenic mechanism of periodontitis was explored through quantitative real-time PCR (qRT-PCR) by inducing inflammatory environment and osteogenic differentiation of hPDLSCs.

RESULTS

Through differential expression analysis and prediction of downstream target genes of DEMs, we created a miRNA-mRNA regulatory network consisting of 29 DEMs and 11 differentially expressed osteogenesis-related genes (DEORGs). In addition, the qRT-PCR results demonstrated that BTBD3, PLAT, AKAP12, SGK1, and GLCE expression levels were significantly upregulated, while those of TIMP3, ZCCHC14, LIN7A, DNAH6, NNT, and ITGA6 were downregulated under the dual effects of inflammatory stimulation and osteogenic induction.

CONCLUSION

DEORGs might be important factors in the osteogenic phase of periodontitis, and the miRNA-mRNA network may shed light on the clarification of the role and mechanism of osteogenesis in periodontitis and contribute to the development of novel therapeutic strategies.

The signaling pathways involved in non-coding RNA regulation during osteogenic differentiation of periodontal tissue-derived cells in the field of periodontitis

Periodontitis is a prevalent oral disease caused by chronic inflammation of the periodontal tissues surrounding the teeth, which can lead to bone loss, tooth loosening, and even tooth loss. This inflammation has a negative impact on the osteogenic differentiation capacity of periodontal tissue-derived cells. Non-coding RNAs (ncRNAs) are a class of RNA molecules that do not encode proteins but can regulate various physiological processes. In this review, we summarized the critical signaling pathways that ncRNAs modulate in osteogenic differentiation of periodontal tissue-derived cells, such as the Wnt, BMP/Smad, NF-κB, and PI3-K/Akt/mTOR pathways. This comprehensive exploration of ncRNA-mediated modulation offers fresh and promising insights for prospective approaches in the management of periodontitis and the advancement of periodontal regeneration therapies.

METTL3-Mediated m6A Modification Regulates the Osteogenic Differentiation through LncRNA CUTALP in Periodontal Mesenchymal Stem Cells of Periodontitis Patients

Objective

Periodontitis is a chronic inflammatory disease that causes loss of periodontal support tissue. Our objective was to investigate the mechanism by which METTL3-mediated N6-methyladenosine modification regulates the osteogenic differentiation through lncRNA in periodontal mesenchymal stem cells in patients with periodontitis (pPDLSCs). Material and Methods. We carried out a series of experiments, including methylated RNA immunoprecipitation-PCR, quantitative real-time polymerase chain reaction, and western blotting. The expressions of alkaline phosphatase (ALP), Runx2, Col1, Runx2 protein level, ALP staining, and Alizarin red staining were used to demonstrate the degree of osteogenic differentiation.

Results

We found that METTL3 was the most significantly differentially expressed methylation-related enzyme in pPDLSCs and promoted osteogenic differentiation of pPDLSCs. METTL3 regulated the stability and expression of lncRNA CUTALP, while lncRNA CUTALP promoted osteogenic differentiation of pPDLSCs by inhibiting miR-30b-3p. At different time points of osteogenic differentiation, lncRNA CUTALP expression was positively correlated with Runx2, while miR-30b-3p showed the opposite pattern. The attenuated osteogenic differentiation induced by METTL3 knockdown was recovered by lncRNA CUTALP overexpression. The attenuated osteogenic differentiation induced by lncRNA CUTALP knockdown could be reversed by the miR-30b-3p inhibitor.

Conclusions

In summary, METTL3/lncRNA CUTALP/miR-30b-3p/Runx2 is a regulatory network in the osteogenic differentiation of pPDLSCs.

Enhancing osteogenic differentiation of MC3T3-E1 cells during inflammation using UPPE/β-TCP/TTC composites via the Wnt/β-catenin pathway

Periodontitis can lead to defects in the alveolar bone, thus increasing the demand for dependable biomaterials to repair these defects. This study aims to examine the pro-osteogenic and anti-bacterial properties of UPPE/β-TCP/TTC composites (composed of unsaturated polyphosphoester [UPPE], β-tricalcium phosphate [β-TCP], and tetracycline [TTC]) under an inflammatory condition. The morphology of MC3T3-E1 cells on the composite was examined using scanning electron microscopy. The toxicity of the composite to MC3T3-E1 cells was assessed using the Alamar-blue assay. The pro-osteogenic potential of the composite was assessed through ALP staining, ARS staining, RT-PCR, and WB. The antimicrobial properties of the composite were assessed using the zone inhibition assay. The results suggest that: (1) MC3T3-E1 cells exhibited stable adhesion to the surfaces of all four composite groups; (2) the UPPE/β-TCP/TTC composite demonstrated significantly lower toxicity to MC3T3-E1 cells; and (3) the UPPE/β-TCP/TTC composite had the most pronounced pro-osteogenic effect on MC3T3-E1 cells by activating the WNT/β-catenin pathway and displaying superior antibacterial properties. UPPE/β-TCP/TTC, as a biocomposite, has been shown to possess antibacterial properties and exhibit excellent potential in facilitating osteogenic differentiation of MC3T3-E1 cells.

Emerging Role of miRNAs in the Pathogenesis of Periodontitis

MicroRNAs (miRNAs) have been found to participate in the pathogenesis of several immune-related conditions through the modulation of the expression of cytokine coding genes and other molecules that affect the activity of the immune system. Periodontitis is an example of these conditions associated with the dysregulation of several miRNAs. Several miRNAs such as let-7 family, miR-125, miR-378, miR-543, miR-302, miR-214, miR-200, miR-146, miR-142, miR-30 and miR-21 have been shown to be dysregulated in patients with periodontitis. miR-146 is the most assessed miRNA in these patients, which is up-regulated in most studies in patients with periodontitis. In the present review, we describe the impact of miRNAs dysregulation on the pathoetiology of periodontitis.

Role of non-coding RNAs in osteoporosis

Osteoporosis, a prevalent bone disorder influenced by genetic and environmental elements, significantly increases the likelihood of fractures and bone weakness, greatly affecting the lives of those afflicted. Yet, the exact epigenetic processes behind the onset of osteoporosis are still unclear. Growing research indicates that epigenetic changes could act as vital mediators that connect genetic tendencies and environmental influences, thereby increasing the risk of osteoporosis and bone fractures. Within these epigenetic factors, certain types of RNA, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), have been recognized as key regulatory elements. These RNA types wield significant influence on gene expression through epigenetic regulation, directing various biological functions essential to bone metabolism. This extensive review compiles current research uncovering the complex ways in which miRNAs, lncRNAs, and circRNAs are involved in the development of osteoporosis, especially in osteoblasts and osteoclasts. Gaining a more profound understanding of the roles these three RNA classes play in osteoporosis could reveal new diagnostic methods and treatment approaches for this incapacitating condition. In conclusion, this review delves into the complex domain of epigenetic regulation via non-coding RNA in osteoporosis. It sheds light on the complex interactions and mechanisms involving miRNAs, lncRNAs, and circRNAs within osteoblasts and osteoclasts, offering an in-depth understanding of the less explored aspects of osteoporosis pathogenesis. These insights not only reveal the complexity of the disease but also offer significant potential for developing new diagnostic methods and targeted treatments. Therefore, this review marks a crucial step in deciphering the elusive complexities of osteoporosis, leading towards improved patient care and enhanced quality of life.

DUXAP8 Promotes LPS-Induced Cell Injury in Pulpitis by Regulating miR-18b-5p/HIF3A

BACKGROUND

The dysregulated long noncoding RNAs (lncRNAs) are implicated in progression of various diseases, including pulpitis. Double homeobox A pseudogene 8 (DUXAP8) has been found to be upregulated in pulpitis. Herein, the functional mechanism of DUXAP8 in lipopolysaccharide (LPS)-induced pulpitis was explored.

MATERIAL AND METHODS

DUXAP8, microRNA-18b-5p (miR-18b-5p), or hypoxia-inducible factor 3A (HIF3A) levels were examined through reverse transcription-quantitative polymerase chain reaction assay. Cell behaviours were determined by Cell Counting Kit-8 assay for cell viability, Ethynyl-2'-deoxyuridine (EdU) assay for cell proliferation, and flow cytometry for cell apoptosis. Protein levels were measured using western blot. Inflammatory reaction was analysed via enzyme-linked immunosorbent assay. Oxidative stress was assessed by commercial kits. Dual-luciferase reporter assay, RNA immunoprecipitation assay, and pull-down assay were used for validation of interaction between targets.

RESULTS

Cell apoptosis, inflammatory reaction, and oxidative stress were induced by LPS in human dental pulp cells (HDPCs). DUXAP8 upregulation and miR-18b-5p downregulation were found in pulpitis. LPS-induced cell injury was relieved after downregulation of DUXAP8. DUXAP8 interacted with miR-18b-5p. The regulation of DUXAP8 was related to miR-18b-5p sponging function in LPS-treated HDPCs. HIF3A served as a target of miR-18b-5p. MiR-18b-5p protected against LPS-induced cell injury through targeting HIF3A. DUXAP8 targeted miR-18b-5p to regulate HIF3A level.

CONCLUSIONS

Results demonstrated that LPS-induced cell injury in pulpitis was promoted by DUXAP8 through mediating miR-18b-5p/HIF3A axis.

lncRNA MEG3 Promotes Osteogenic Differentiation of Tendon Stem Cells Via the miR-129-5p/TCF4/β-Catenin Axis and thus Contributes to Trauma-Induced Heterotopic Ossification

BACKGROUND

Heterotopic ossification (HO) is one of the most intractable conditions following injury to the musculoskeletal system. In recent years, much attention has been paid to the role of lncRNA in musculoskeletal disorders, but its role in HO was still unclear. Therefore, this study attempted to determine the role of lncRNA MEG3 in the formation of post-traumatic HO and further explore the underlying mechanisms.

RESULTS

On the basis of high-throughput sequencing and qPCR validation, elevated expression of the lncRNA MEG3 was shown during traumatic HO formation. Accordingly, in vitro experiments demonstrated that lncRNA MEG3 promoted aberrant osteogenic differentiation of tendon-derived stem cells (TDSCs). Mechanical exploration through RNA pulldown, luciferase reporter gene assay and RNA immunoprecipitation assay identified the direct binding relationship between miR-129-5p and MEG3, or miR-129-5p and TCF4. Further rescue experiments confirmed the miR-129-5p/TCF4/β-catenin axis to be downstream molecular cascade responsible for the osteogenic-motivating effects of MEG3 on the TDSCs. Finally, experiments in a mouse burn/tenotomy model corroborated the promoting effects of MEG3 on the formation of HO through the miR-129-5p/TCF4/β-catenin axis.

CONCLUSIONS

Our study demonstrated that the lncRNA MEG3 promoted osteogenic differentiation of TDSCs and thus the formation of heterotopic ossification, which could be a potential therapeutic target.

Decoding the role of long non-coding RNAs in periodontitis: A comprehensive review

Periodontitis is an inflammatory disease characterized by the pathological loss of alveolar bone and the adjacent periodontal ligament. It is considered a disease that imposes a substantial health burden, with an incidence rate of 20-50%. The etiology of periodontitis is multifactorial, with genetic factors accounting for approximately half of severe cases. Studies have revealed that long non-coding RNAs (lncRNAs) play a pivotal role in periodontitis pathogenesis. Accumulating evidence suggests that lncRNAs have distinct regulatory mechanisms, enabling them to control numerous vital processes in periodontal cells, including osteogenic differentiation, inflammation, proliferation, apoptosis, and autophagy. In this review, we summarize the diverse roles of lncRNAs in the pathogenesis of periodontitis, shedding light on the underlying mechanisms of disease development. By highlighting the potential of lncRNAs as biomarkers and therapeutic targets, this review offers a new perspective on the diagnosis and treatment of periodontitis, paving the way for further investigation into the field of lncRNA-based therapeutics.

Epigenetic regulation of osteogenic differentiation of periodontal ligament stem cells in periodontitis

Periodontitis is an inflammatory disease characterized by alveolar bone loss. Periodontal ligament stem cells (PDLSCs) have osteogenic differentiation potential, which can be influenced by epigenetics regulation in periodontitis. Therefore, this review aimed to shed light on the role of different epigenetic mechanisms in the osteogenic differentiation of PDLSCs and to consider the prospects of their possible therapeutic applications in periodontitis. Databases MEDLINE (through PubMed) and Web of Science were searched for the current knowledge of epigenetics in osteogenic differentiation of PDLSCs using the keywords "periodontal ligament stem cells", "epigenetic regulation", "epigenetics", "osteogenic differentiation", and "osteogenesis". All studies introducing epigenetic regulation and PDLSCs were retrieved. This review shows that epigenetic factors like DNMT, KDM6A, HDACi, some miRNAs, and lncRNAs can induce the osteogenic differentiation of PDLSCs in the noninflammatory microenvironment. However, the osteogenic differentiation of PDLSCs is inhibited in the inflammatory microenvironment through the upregulated DNA methylation of osteogenesis-related genes and specific changes in histone modification and noncoding RNA. Epigenetics of osteogenic differentiation of PDLSCs in inflammation exhibits the contrary effect compared with a noninflammatory environment. The application of epigenetic drugs to regulate the abnormal epigenetic status in periodontitis and focus on alveolar bone regeneration is promising.

FOXO1 regulates osteogenic differentiation of periodontal ligament stem cells through the METTL3 signaling pathway

BACKGROUND

Periodontitis is a chronic inflammation that occurs in periodontal tissue and has a high incidence rate. Periodontal ligament stem cells (PDLSCs) are ideal candidates for periodontal tissue and bone regeneration in patients with periodontitis. The purpose of this work was to analyze the molecular mechanisms that affect the osteogenic differentiation of PDLSCs.

METHODS

In this work, qRT‒PCR was used to detect the mRNA expression level of FOXO1 in clinical tissues and PDLSCs. Alkaline phosphatase (ALP) staining and Alizarin red S (ARS) staining were used to detect the degree of osteogenic differentiation of PDLSCs. qRT‒PCR and western blotting were used to measure the levels of the early osteogenic markers COL1A1 and RUNX2. The JASPAR online database was used to predict FOXO1-regulated genes.

RESULTS

FOXO1 was generally expressed at low levels in clinical samples from patients with periodontitis. We provided evidence that overexpression of FOXO1 promoted osteogenic differentiation in PDLSCs. In addition, both in vitro and rescue experiments showed that FOXO1 regulated METTL3. FOXO1 affected osteogenic differentiation mainly by regulating METTL3 modification of the PI3K/AKT pathway.

CONCLUSIONS

FOXO1 activated the PI3K/AKT signaling pathway by transcriptionally activating METTL3. This effect promoted the osteogenic differentiation of PDLSCs.

A novel LncRNA SPIRE1/miR-181a-5p/PRLR axis in mandibular bone marrow-derived mesenchymal stem cells regulates the Th17/Treg immune balance through the JAK/STAT3 pathway in periodontitis

Periodontitis is a microbial-related chronic inflammatory disease associated with imbalanced differentiation of Th17 cells and Treg cells. Bone marrow-derived mesenchymal stem cells (BM-MSCs) possess wide immunoregulatory properties. Long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) contribute to the immunomodulation in the pathological mechanisms of inflammatory diseases. However, critical lncRNAs/miRNAs involved in immunomodulation of mandibular BM-MSCs largely remain to be identified. Here, we explored the molecular mechanisms behind the defective immunomodulatory ability of mandibular BM-MSCs under the periodontitis settings. We found that mandibular BM-MSCs from P. gingivalis-induced periodontitis mice had significantly reduced expression of LncRNA SPIRE1 than that from normal control mice. LncRNA SPIRE1 knockdown in normal BM-MSCs caused Th17/Treg cell differentiation imbalance during the coculturing of BM-MSCs and CD4 T cells. In addition, LncRNA SPIRE1 was identified as a competitive endogenous RNA that sponges miR-181a-5p in BM-MSCs. Moreover, miR-181a-5p inhibition attenuated the impact of LncRNA SPIRE1 knockdown on the ability of BM-MSCs in modulating Th17/Treg balance. Prolactin receptor (PRLR) was validated as a downstream target of miR-181a-5p. Notably, targeted knockdown of LncRNA SPIRE1 or PRLR or transfection of miR-181a-5p mimics activated the JAK/STAT3 signaling in normal BM-MSCs, while treatment with STAT3 inhibitor C188-9 restored the immunomodulatory properties of periodontitis-associated BM-MSCs. Furthermore, BM-MSCs with miR-181a-5p inhibition or PRLR-overexpression showed enhanced in vivo immunosuppressive properties in the periodontitis mouse model. Our results indicate that the JAK/STAT3 pathway is involved in the immunoregulation of BM-MSCs, and provide critical insights into the development of novel targeted therapies against periodontitis.

LncRNA00638 promotes the osteogenic differentiation of periodontal mesenchymal stem cells from periodontitis patients under static mechanical strain

BACKGROUND

The osteogenic differentiation capacity of periodontal mesenchymal stem cells (PDLSCs) can be influenced by different levels of static mechanical strain (SMS) in an inflammatory microenvironment. Long non-coding RNAs (lncRNAs) are involved in various physiological processes. However, the mechanisms by which lncRNAs regulate the osteogenic differentiation of PDLSCs remain unclear.

METHODS

We investigated the responses of PDLSCs obtained from periodontitis patients and healthy people to 8% and 12%SMS. Gene microarray and bioinformatics analyses were implemented and identified lncRNA00638 as a target gene for the osteogenesis of PDLSCs from periodontitis patients under SMS. Competing endogenous RNA (ceRNA) network analysis was applied and predicted interactions among lncRNA00638, miRNA-424-5p, and fibroblast growth factor receptor 1 (FGFR1). Gene expression levels were regulated by lentiviral vectors. Cell Counting Kit-8 assays, alkaline phosphatase assays, and Alizarin Red S staining were used to examine the osteogenic potential. RT-qPCR and Western blot were performed to detect the expression levels of related genes and proteins.

RESULTS

We found that 8% and 12% SMS exerted distinct effects on HPDLSCs and PPDLSCs, with 12% SMS having the most significant effect. By microarray analysis, we detected differentially expressed lncRNAs/mRNAs between 12% SMS strained and static PPDLSCs, among which lncRNA00638 was detected as a positive target gene to promote the osteogenic differentiation of PPDLSCs under SMS loading. Mechanistically, lncRNA00638 may act as a ceRNA for miR-424-5p to compete with FGFR1. In this process, lncRNA00638 and miR-424-5p suppress each other and form a network to regulate FGFR1.

CONCLUSIONS

Our findings demonstrate that the lncRNA00638/miRNA-424-5p/FGFR1 regulatory network is actively involved in the regulation of PDLSC osteogenic differentiation from periodontitis patients under SMS loading, which may provide evidence for optimizing orthodontic treatments in patients with periodontitis.

Integrative Analysis of ceRNA Networks in human periodontal ligament stem cells under hypoxia

OBJECTIVE

This study aims to investigate the regulatory effect of hypoxia on human periodontal ligament stem cells (PDLSCs) through RNA sequencing (RNA SEQ). Human PDLSCs were cultured in normoxia (20% O₂ ) or hypoxia (2% O₂ ).

MATERIAL AND METHODS

Total RNA was extracted and sequenced. The expression profiles of circRNAs, lncRNAs, and miRNAs were determined, and the lncRNA/circRNA-miRNA-mRNA networks were analyzed.

RESULTS

In total, 15 miRNAs, 449 lncRNAs, and 53 circRNAs were differentially expressed. Among them, 21 circRNAs, 262 lncRNAs, 5 miRNAs, and 5 mRNAs were selected to construct competing endogenous RNA (ceRNA) networks. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were carried out to explore potential related pathways and regulatory functions. Several ceRNA axes (lncRNA-FTX/circRNA-FAT1-hsa-miR-4781-3p-SMAD5 and circRNA LPAR1-hsa-miR-342-3p-ADAR) may provide a theoretical basis on the study of osteogenic differentiation of PDLSCs under hypoxia.

CONCLUSION

This study revealed that the expression profiles of circRNAs, lncRNAs, and miRNAs had changed significantly in PDLSCs cultured in 2% O₂ ; specific circRNAs/lncRNAs may play a competitive role in the differentiation of PDLSCs.

Effect of LSD1 on osteogenic differentiation of human periodontal ligament stem cells in periodontitis

OBJECTIVE

Periodontitis is a chronic inflammation of periodontal tissues. This study is expected to assess the effect of LSD1 on the osteogenic differentiation of hPDLSCs in periodontitis.

METHODS

hPDLSCs were separated, cultivated, and identified, and then treated by LPS to induce inflammatory microenvironment and subjected to osteogenic differentiation. Subsequently, LSD1 expression was determined, and then silenced to assess its effect on hPDLSCs. Next, the binding relation between LSD1 and miR-590-3p was analyzed. miR-590-3p expression was detected and then overexpressed to evaluate its role in hPDLSCs in periodontitis. Afterward, the relation between LSD1 and OSX was analyzed. H3K4me2 level and OSX transcription were measured, and the role of H3K4me2 was determined. Additionally, the role of OSX in hPDLSCs was verified.

RESULTS

LSD1 was poorly expressed after osteogenic differentiation of hPDLSCs while it was rescued upon LPS induction. The osteogenic differentiation of hPDLSC in periodontitis was strengthened upon LSD1 downregulation. Besides, miR-590-3p targeted LSD1 transcription, and LSD1 inhibited OSX transcription via H3K4me2 demethylation. miR-590-3p overexpression improved osteogenic differentiation of hPDLSCs in periodontitis. But this improvement was annulled by OSX inhibition.

CONCLUSION

miR-590-3p targeted LSD1 transcription and upregulated H3K4me2 methylation to promote OSX transcription, thereby encouraging osteogenic differentiation of hPDLSCs in periodontitis.

Epigenetic regulation of dental-derived stem cells and their application in pulp and periodontal regeneration

Dental-derived stem cells have excellent proliferation ability and multi-directional differentiation potential, making them an important research target in tissue engineering. An increasing number of dental-derived stem cells have been discovered recently, including dental pulp stem cells (DPSCs), stem cells from exfoliated deciduous teeth (SHEDs), stem cells from apical papilla (SCAPs), dental follicle precursor cells (DFPCs), and periodontal ligament stem cells (PDLSCs). These stem cells have significant application prospects in tissue regeneration because they are found in an abundance of sources, and they have good biocompatibility and are highly effective. The biological functions of dental-derived stem cells are regulated in many ways. Epigenetic regulation means changing the expression level and function of a gene without changing its sequence. Epigenetic regulation is involved in many biological processes, such as embryonic development, bone homeostasis, and the fate of stem cells. Existing studies have shown that dental-derived stem cells are also regulated by epigenetic modifications. Pulp and periodontal regeneration refers to the practice of replacing damaged pulp and periodontal tissue and restoring the tissue structure and function under normal physiological conditions. This treatment has better therapeutic effects than traditional treatments. This article reviews the recent research on the mechanism of epigenetic regulation of dental-derived stem cells, and the core issues surrounding the practical application and future use of pulp and periodontal regeneration.

LIPUS as a potential strategy for periodontitis treatment: A review of the mechanisms

Periodontitis is a chronic inflammatory condition triggered by oral bacteria. A sustained inflammatory state in periodontitis could eventually destroy the alveolar bone. The key objective of periodontal therapy is to terminate the inflammatory process and reconstruct the periodontal tissues. The traditional Guided tissue regeneration (GTR) procedure has unstable results due to multiple factors such as the inflammatory environment, the immune response caused by the implant, and the operator's technique. Low-intensity pulsed ultrasound (LIPUS), as acoustic energy, transmits the mechanical signals to the target tissue to provide non-invasive physical stimulation. LIPUS has positive effects in promoting bone regeneration, soft-tissue regeneration, inflammation inhibition, and neuromodulation. LIPUS can maintain and regenerate alveolar bone during an inflammatory state by suppressing the expression of inflammatory factors. LIPUS also affects the cellular behavior of periodontal ligament cells (PDLCs), thereby protecting the regenerative potential of bone tissue in an inflammatory state. However, the underlying mechanisms of the LIPUS therapy are still yet to be summarized. The goal of this review is to outline the potential cellular and molecular mechanisms of periodontitis-related LIPUS therapy, as well as to explain how LIPUS manages to transmit mechanical stimulation into the signaling pathway to achieve inflammatory control and periodontal bone regeneration.

Long Noncoding RNA and mRNA m6A Modification Analyses of Periodontal Ligament Stem Cells from the Periodontitis Microenvironment Exposed to Static Mechanical Strain

Periodontal ligament stem cells (PDLSCs) play important roles in orthodontic tooth movement (OTM) and can respond to mechanical stress. Our previous study demonstrated that periodontal ligament stem cells derived from periodontitis tissue (pPDLSCs) are more sensitive to static mechanical strain (SMS) than those derived from healthy tissue (hPDLSCs) and reported the long noncoding RNA (lncRNA) expression profiles of pPDLSCs exposed to SMS. An increasing number of lncRNAs have been reported by various studies to be associated with the osteogenic differentiation of mesenchymal stem cells. Many studies have demonstrated that the n6-methyladenosine (m6A) modification exerts important effects on lncRNA and mRNA regulation of cell behaviors. However, the regulatory effects of lncRNA and mRNA m6A modification on PDLSCs have not been studied. Therefore, we performed an m6A microarray assay with pPLDSCs and hPDLSCs exposed to 12% SMS and found that 143 lncRNAs and 739 mRNAs were differentially methylated. These RNAs were thought to be involved in multiple differentiation and inflammatory responses. Moreover, we found that METTL3, an essential protein in the m6A system, was expressed at lower levels in the strain-exposed pPDLSCs than in strain-exposed hPLDSCs, and METTL3 promoted the osteogenic differentiation of pPDLSCs.

Progress in the Study of Non-Coding RNAs in Multidifferentiation Potential of Dental-Derived Mesenchymal Stem Cells

For decades, the desire for tissue regeneration has never been quenched. Dental-derived mesenchymal stem cells (DMSCs), with the potential of self-renewal and multi-directional differentiation, have attracted much attention in this topic. Growing evidence suggests that non-coding RNAs (ncRNAs) can activate various regulatory processes. Even with a slight decrease or increase in expression, ncRNAs can weaken or even subvert cellular fate. Therefore, a systematic interpretation of ncRNAs that guide the differentiation of DMSCs into cells of other tissue types is urgently needed. In this review, we introduce the roles of ncRNAs in the differentiation of DMSCs, such as osteogenic differentiation, odontogenic differentiation, neurogenic differentiation, angiogenic differentiation and myogenic differentiation. Additionally, we illustrate the regulatory mechanisms of ncRNAs in the differentiation of DMSCs, such as epigenetic regulation, transcriptional regulation, mRNA modulation, miRNA sponges and signalling. Finally, we summarize the types and mechanisms of ncRNAs in the differentiation of DMSCs, such as let-7 family, miR-17∼92 family, miR-21, lncRNA H19, lncRNA ANCR, lncRNA MEG3, circRNA CDR1as and CircRNA SIPA1L1. If revealing the intricate relationship between ncRNAs and pluripotency of DMSCs 1 day, the application of DMSCs in regenerative medicine and tissue engineering will be improved. Our work could be an important stepping stone towards this future.

Long non-coding RNA Linc01133 promotes osteogenic differentiation of human periodontal ligament stem cells via microRNA-30c / bone gamma-carboxyglutamate protein axis

Periodontitis is a chronic inflammation caused by the deposition of dental plaque on the tooth surface. Human periodontal ligament stem cells (hPDLSCs) have the potential of osteogenic differentiation. Long non-coding RNAs (lncRNAs) are collectively involved in periodontitis. This study was designed to explore the roles of Linc01133 in osteogenic differentiation of hPDLSCs. hPDLSCs obtained from the periodontal ligament (PDL) of patients with periodontitis were used to collect Linc01133, microRNA-30c (miR-30c), and bone gamma-carboxyglutamate protein (BGLAP) expression data, and their expression changes were traced during osteogenic differentiation of hPDLSCs. Quantitative reverse-transcription polymerase chain reaction as well as western blotting were used to analyze the levels of RNAs and proteins. Dual-luciferase reporter and RNA pull-down assays demonstrated the relationship between Linc01133, miR-30c, and BGLAP. Furthermore, alkaline phosphatase (ALP) staining and alizarin red staining were applied to evaluate the degree of osteogenic differentiation. Linc01133 was downregulated in the PDL of patients with periodontitis. Upregulated Linc01133 promoted osteogenic differentiation of hPDLSCs. Linc01133 could inhibit miR-30c expression by sponging miR-30c. miR-30c suppressed osteogenic differentiation. Additionally, miR-30c targeted BGLAP. Knockdown of BGLAP abrogated the effects of decreased miR-30c on osteogenic differentiation of hPDLSCs. Linc01133 acted as a ceRNA to regulate osteogenic differentiation of hPDLSCs via the miR-30c/BGLAP axis. Therefore, Linc01133 may participate in the progress of periodontitis.

Emerging role of epigenetic regulations in periodontitis: a literature review

Periodontitis is mainly initiated by periodontal pathogens including Porphyromonas gingivalis, and bad living habits such as smoking aggravate its incidence and severity. The development of periodontitis is closely related to the host's immune responses and the secretion of various cytokine networks. Moreover, periodontitis has an important connection with the development of systemic diseases. Recently, epigenetics which is a fast-developing hot research area has provided new insights into the research of various diseases including periodontitis. Epigenetics is an important supplement to the regulation of gene expression. The study of epigenetics is about causing heritable gene expression or cell phenotype changes through certain mechanisms without changing the DNA sequence. It mainly includes histone modification, DNA methylation, non-coding RNA and the latest research hotspot m6A RNA methylation. In the review, we comprehensively summarize the latest literature on the potential epigenetic regulations in various aspects of periodontitis.

Effects of nuclear factor-κB signaling pathway on periodontal ligament stem cells under lipopolysaccharide-induced inflammation

Lipopolysaccharide (LPS) induces inflammatory stress and apoptosis. This study focused on the effect of nuclear factor kappa B (NF-κB) signaling pathway on proliferation and osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) after LPS induction and its mechanism. We first isolated hPDLSCs from human tooth root samples in vitro. Then, flow cytometry detected positive expression of cell surface antigens CD146 and STRO-1 and negative expression of CD45, suggesting the hPDLSCs were successfully isolated. LPS significantly induced increased apoptosis and diminished proliferation of hPDLSCs. The NF-κB pathway agonist phorbol 12-myristate 13-acetate (PMA) or p65 overexpression inhibited the proliferation of LPS-treated hPDLSCs and promoted apoptosis. PMA also promoted LPS-induced up-regulation of the expression of inflammatory factors TNF-α and IL-6 and down-regulation of the expression of anti-inflammatory factor IL-10. Additionally, LPS was confirmed to lead to a reduction of alkaline phosphatase (ALP) activity, calcium nodules, and expression of osteogenic markers Runt-related transcription factor 2 (Runx2) and osteopontin. This reduction could be promoted by PMA. Western blotting further indicated that PMA could promote LPS-induced decrease of expression of p65 (cytoplasm), and total cellular proteins IKKα and IKKβ in hPDLSCs, while protein expression of p-IκBα (cytoplasm) and p65 (nucleus), and p-IκBα/IκBα ratio was elevated. By contrast, inhibition of the NF-κB pathway (PDTC) or small-interfering RNA targeting NF-κB/p65 (p65 siRNA) showed the opposite results. In conclusion, activation of NF-κB signaling in LPS-induced inflammatory environment can inhibit the proliferation and osteogenic differentiation of hPDLSCs. This study provides a theory foundation for the clinical treatment of periodontitis.

Effects of long noncoding RNA H19 on cementoblast differentiation, mineralisation, and proliferation

OBJECTIVE

Cementum which is a layer of thin and bone-like mineralised tissue covering tooth root surface is deposited and mineralised by cementoblasts. Recent studies suggested long noncoding RNA H19 (H19) promotes osteoblast differentiation and matrix mineralisation, however, the effect of H19 on cementoblasts remains unknown. This study aimed to clarify the regulatory effects of H19 on cementoblast differentiation, mineralisation, and proliferation.

MATERIAL AND METHODS

An immortalised murine cementoblast cell line OCCM-30 was used in this study. H19 expression was examined by real-time quantitative polymerase chain reaction (RT-qPCR) during OCCM-30 cell differentiation. OCCM-30 cells were transfected with lentivirus or siRNA to up-regulate or down-regulate H19, then the levels of runt-related transcription factor 2 (Runx2), osterix (Sp7), alkaline phosphatase (Alpl), bone sialoprotein (Ibsp), osteocalcin (Bglap) were tested by RT-qPCR or western blot. Alizarin red staining, ALP activity assay and MTS assay were performed to determine the mineralisation and proliferation ability of OCCM-30 cells.

RESULTS

H19 was dramatically increased during OCCM-30 cell differentiation. Overexpression of H19 increased the levels of Runx2, Sp7, Alpl, Ibsp, and Bglap and enhanced ALP activity and the formation of mineral nodules. While down-regulation of H19 suppressed the above cementoblast differentiation genes and inhibited ALP activity and mineral nodule formation. However, the proliferation of OCCM-30 cells was not affected.

CONCLUSIONS

H19 promotes the differentiation and mineralisation of cementoblasts without affecting cell proliferation.

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

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

Role of lncRNAs into Mesenchymal Stromal Cell Differentiation

Currently, findings support that 75% of the human genome is actively transcribed, but only 2% is translated into a protein, according to databases such as ENCODE (Encyclopedia of DNA Elements) [1]. The development of high-throughput sequencing technologies, computational methods for genome assembly and biological models have led to the realization of the importance of the previously unconsidered non-coding fraction of the genome. Along with this, noncoding RNAs have been shown to be epigenetic, transcriptional and post-transcriptional regulators in a large number of cellular processes [2]. Within the group of non-coding RNAs, lncRNAs represent a fascinating field of study, given the functional versatility in their mode of action on their molecular targets. In recent years, there has been an interest in learning about lncRNAs in MSC differentiation. The aim of this review is to address the signaling mechanisms where lncRNAs are involved, emphasizing their role in either stimulating or inhibiting the transition to differentiated cell. Specifically, the main types of MSC differentiation are discussed: myogenesis, osteogenesis, adipogenesis and chondrogenesis. The description of increasingly new lncRNAs reinforces their role as players in the well-studied field of MSC differentiation, allowing a step towards a better understanding of their biology and their potential application in the clinic.

Stem Cell Therapy in Chronic Periodontitis: Host Limitations and Strategies

The treatment of chronic periodontitis is undergoing a transition from simple plaque removal and replacement with substitute materials to regenerative therapy, in which stem cells play an important role. Although stem cell-based periodontal reconstruction has been widely explored, few clinical regeneration studies have been reported. The inflammatory lesions under the impact of host factors such as local microbial–host responses, may impede the regenerative properties of stem cells and destroy their living microenvironment. Furthermore, systemic diseases, in particular diabetes mellitus, synergistically shape the disordered host-bacterial responses and exacerbate the dysfunction of resident periodontal ligament stem cells (PDLSCs), which ultimately restrain the capacity of mesenchymal stromal cells (MSCs) to repair the damaged periodontal tissue. Accordingly, precise regulation of an instructive niche has become a promising approach to facilitate stem cell-based therapeutics for ameliorating periodontitis and for periodontal tissue regeneration. This review describes host limitations and coping strategies that influence resident or transplanted stem cell-mediated periodontal regeneration, such as the management of local microbial–host responses and rejuvenation of endogenous PDLSCs. More importantly, we recommend that active treatments for systemic diseases would also assist in recovering the limited stem cell function on the basis of amelioration of the inflammatory periodontal microenvironment.

Deciphering the Epigenetic Code of Stem Cells Derived From Dental Tissues

Stem cells derived from dental tissues (DSCs) exhibit multipotent regenerative potential in pioneering tissue engineering regimens. The multipotency of DSCs is critically regulated by an intricate range of factors, of which the epigenetic influence is considered vital. To gain a better understanding of how epigenetic alterations are involved in the DSC fate determination, the present review overviews the current knowledge relating to DSC epigenetic modifications, paying special attention to the landscape of epigenetic modifying agents as well as the related signaling pathways in DSC regulation. In addition, insights into the future opportunities of epigenetic targeted therapies mediated by DSCs are discussed to hold promise for the novel therapeutic interventions in future translational medicine.

Comprehensive analysis of the long noncoding RNA-associated competitive endogenous RNA network in the osteogenic differentiation of periodontal ligament stem cells

BACKGROUD

The mechanism implicated in the osteogenesis of human periodontal ligament stem cells (PDLSCs) has been investigated for years. Previous genomics data analyses showed that long noncoding RNA (lncRNA), microRNA (miRNA) and messenger RNA (mRNA) have significant expression differences between induced and control human PDLSCs. Competing for endogenous RNAs (ceRNA), as a widely studied mechanism in regenerative medicine, while rarely reported in periodontal regeneration. The key lncRNAs and their ceRNA network might provide new insights into molecular therapies of periodontal regeneration based on PDLSCs.

RESULTS

Two networks reflecting the relationships among differentially expressed RNAs were constructed. One ceRNA network was composed of 6 upregulated lncRNAs, 280 upregulated mRNAs, and 18 downregulated miRNAs. The other network contained 33 downregulated lncRNAs, 73 downregulated mRNAs, and 5 upregulated miRNAs. Functional analysis revealed that 38 GO terms and 8 pathways related with osteogenesis were enriched. Twenty-four osteogenesis-related gene-centred lncRNA-associated ceRNA networks were successfully constructed. Among these pathways, we highlighted MAPK and TGF-beta pathways that are closely related to osteogenesis. Subsequently, subnetworks potentially linking the GO:0001649 (osteoblast differentiation), MAPK and TGF-beta pathways were constructed. The qRT-PCR validation results were consistent with the microarray analysis.

CONCLUSION

We construct a comprehensively identified lncRNA-associated ceRNA network might be involved in the osteogenesis of PDLSCs, which could provide insights into the regulatory mechanisms and treatment targets of periodontal regeneration.

lncRNA FGD5-AS1 and miR-130a Can Be Used for Prognosis Analysis of Patients with Chronic Periodontitis

Background

lncRNA and microRNA affect the occurrence and development of many diseases, so they are expected to become diagnostic or predictive indicators. But the relationship between lncRNA FGD5-AS1 and miR-130a and the prognosis of chronic periodontitis is still unclear. The purpose of this study is to explore the prognostic value of the two in chronic periodontitis.

Objective

This study set out to investigate the prognostic value of lncRNA FGD5-AS1 and miR-130a in chronic periodontitis.

Methods

Eighty-seven patients with chronic periodontitis who visited our hospital from March 2016 to August 2017 were collected as an observation group (OG), and 72 subjects with periodontal health who underwent physical examination at the same time were collected as a control group (CG). The FGD5-AS1 and miR-130a expression levels of subjects in the two groups were compared, and prognosis of 87 patients who were reviewed one year later was counted. The expression levels of patients with different prognoses were compared when they were admitted to our hospital. We drew the ROC curve and explored the prognostic value of FGD5-AS1 and miR-130a. The risk factors for adverse prognosis were analyzed through logistic regression.

Results

FGD5-AS1 was lowly expressed in patients, while miR-130a was highly expressed. FGD5-AS1 and miR-130a had certain diagnostic and predictive value in chronic periodontitis and patient prognosis. The higher the periodontal pocket, the higher the attachment loss. Lower FGD5-AS1 and higher miR-130a levels were independent prognostic risk factors.

Conclusion

lncRNA FGD5-AS1 is lowly expressed in patients with chronic periodontitis, while miR-130a is highly expressed. Both of them have certain diagnostic and prognostic value in chronic periodontitis and may be potential diagnostic and prognostic indicators.

Long Non-coding RNAs LOC100126784 and POM121L9P Derived From Bone Marrow Mesenchymal Stem Cells Enhance Osteogenic Differentiation via the miR-503-5p/SORBS1 Axis

Long non-coding RNAs (lncRNAs) play pivotal roles in mesenchymal stem cell differentiation. However, the mechanisms by which non-coding RNA (ncRNA) networks regulate osteogenic differentiation remain unclear. Therefore, our aim was to identify RNA-associated gene and transcript expression profiles during osteogenesis in bone marrow mesenchymal stem cells (BMSCs). Using transcriptome sequencing for differentially expressed ncRNAs and mRNAs between days 0 and 21 of osteogenic differentiation of BMSCs, we found that the microRNA (miRNA) miR-503-5p was significantly downregulated. However, the putative miR-503-5p target, sorbin and SH3 domain containing 1 (SORBS1), was significantly upregulated in osteogenesis. Moreover, through lncRNA-miRNA-mRNA interaction analyses and loss- and gain-of-function experiments, we discovered that the lncRNAs LOC100126784 and POM121L9P were abundant in the cytoplasm and enhanced BMSC osteogenesis by promoting SORBS1 expression. In contrast, miR-503-5p reversed this effect. Ago2 RNA-binding protein immunoprecipitation and dual-luciferase reporter assays further validated the direct binding of miR-503-5p to LOC100126784 and POM121L9P. Furthermore, SORBS1 knockdown suppressed early osteogenic differentiation in BMSCs, and co-transfection with SORBS1 small interfering RNAs counteracted the BMSCs’ osteogenic capacity promoted by LOC100126784- and POM121L9P-overexpressing lentivirus plasmids. Thus, the present study demonstrated that the lncRNAs LOC100126784 and POM121L9P facilitate the osteogenic differentiation of BMSCs via the miR-503-5p/SORBS1 axis, providing potential therapeutic targets for treating osteoporosis and bone defects.

miR-205 and HMGB1 expressions in chronic periodontitis patients and their associations with the inflammatory factors

OBJECTIVE

This paper sets out to investigate the miR-205 and HMGB1 expressions in chronic periodontitis (PO) patients and their associations with the inflammatory factors.

METHODS

From February 2016 to May 2018, 68 PO patients treated in our hospital were recruited for the study and placed in a patient group (PG), and 60 healthy volunteers were also recruited and placed in a healthy group (HG). Serum samples were collected from both groups for the identification of miR-205 using qPCR, as well as to determine the HMGB1 and inflammatory factor (IL-1β, IL-6, TNF-α) expression levels using ELISA. The correlations of the miR-205 and HMGB1 expression levels with the periodontal clinical indicators and the inflammatory factors were analyzed using a correlation analysis.

RESULTS

In comparison with the HG expression, the serum miR-205 expression was lower, and the HMGB1 was elevated in PG (P < 0.05). An ROC curve analysis showed that the areas under the curve (AUCs) of the serum miR-205 and HMGB1 expressions in diagnosing PO were 0.936 and 0.955 respectively. However, the serum miR-205 expression in PG increased while the HMGB1 expression decreased post treatment (P < 0.05). A correlation analysis revealed an inverse association between the serum miR-205 expression levels and the periodontal clinical indicators [bleeding index (BI), probing depth (PD), plaque index (PLI), and attachment loss (AL)], and the inflammatory factors [interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α)], but there was a positive association between the HMGB1 expression level and these parameters.

CONCLUSIONS

miR-205 and HMGB1 are closely related to the progression of PO, and may be candidate biomarkers for the diagnosis and treatment of PO.

Fluid shear stress regulates osteoblast proliferation and apoptosis via the lncRNA TUG1/miR-34a/FGFR1 axis

LncRNAs and microRNAs play critical roles in osteoblast differentiation and bone formation. However, their exact roles in osteoblasts under fluid shear stress (FSS) and the possible mechanisms remain unclear. The aim of this study was to explore whether and how miR‐34a regulates osteoblast proliferation and apoptosis under FSS. In this study, FSS down‐regulated miR‐34a levels of MC3T3‐E1 cells. MiR‐34a up‐regulation attenuated FSS‐induced promotion of proliferation and suppression of apoptosis. Luciferase reporter assay revealed that miR‐34a directly targeted FGFR1. Moreover, miR‐34a regulated osteoblast proliferation and apoptosis via FGFR1. Further, we validated that lncRNA TUG1 acted as a competing endogenous RNA (ceRNA) to interact with miR‐34a and up‐regulate FGFR1 protein expression. Furthermore, lncRNA TUG1 could promote proliferation and inhibit apoptosis. Taken together, our study revealed the key role of the lncRNA TUG1/miR‐34a/FGFR1 axis in FSS‐regulated osteoblast proliferation and apoptosis and may provide potential therapeutic targets for osteoporosis.

MALAT1 regulates osteogenic differentiation of human periodontal ligament stem cells through mediating miR-155-5p/ETS1 axis

BACKGROUND

Osteogenic differentiation of human periodontal ligament stem cells is essential to periodontal regeneration treatment for periodontitis. This study investigated the mechanism of lncRNAs-related osteogenic differentiation.

METHODS

Human periodontal ligament stem cells were extracted from human periodontal ligament and identified via flow cytometry. After being induced into osteogenic differentiation for three weeks using osteoblast inducing conditional media, human periodontal ligament stem cells were transfected with siRNA-MALAT1, or miR-155-5p inhibitor. Human periodontal ligament stem cells osteogenesis was observed by alkaline phosphatase staining, followed by alizarin red staining for evaluating mineralized nodes formation. Runt-related gene 2, collagen-1 and osteocalcin expressions were assessed by western blot and qRT-PCR.

RESULTS

MALAT1 expression was assumed a negative correlation with miR-155-5p expression which was dropping over time in differentiating human periodontal ligament stem cells. MALAT1 could bind with miR-155-5p, and E26 transformation specific-1 (ETS1) was the targeted gene of miR-155-5p. Silenced MALAT1 suppressed ALP activity and mineralized nodes formation and inhibited the expressions of runt-related gene 2, collagen-1 and osteocalcin in differentiating human periodontal ligament stem cells, while miR-155-5p inhibitor reversed the effect of si-MALAT1 on differentiation of human periodontal ligament stem cells.

CONCLUSION

MALAT1 modulated differentiation of human periodontal ligament stem cells via regulating miR-155-5p.

Long non-coding RNAs: Emerging roles in periodontitis

Periodontitis is a major burden of public health, affecting 20%-50% of the global population. It is a complex inflammatory disease characterized by the destruction of supporting structures of the teeth, leading to tooth loss and the emergence or worsening of systematic diseases. Understanding the molecular mechanisms underlying the physiopathology of periodontitis is beneficial for targeted therapeutics. Long non-coding RNAs (lncRNAs), transcripts made up of more than 200 nucleotides, have emerged as novel regulators of many biological and pathological processes. Recently, an increasing number of dysregulated lncRNAs have been found to be implicated in periodontitis. In this review, an overview of lncRNAs, including their biogenesis, characteristics, function mechanisms and research approaches, is provided. And we summarize recent research reports on the emerging roles of lncRNAs in regulating proliferation, apoptosis, inflammatory responses, and osteogenesis of periodontal cells to elucidate lncRNAs related physiopathology of periodontitis. Furthermore, we have highlighted the underlying mechanisms of lncRNAs in periodontitis pathology by interacting with microRNAs. Finally, the potential clinical applications, current challenges, and prospects of lncRNAs as diagnostic and prognostic biomarkers and therapeutic targets for periodontitis disease are discussed.

The role of long noncoding RNA THAP9-AS1 in the osteogenic differentiation of dental pulp stem cells via the miR-652-3p/VEGFA axis

Dental pulp stem cells (DPSCs) are multipotent and may play crucial roles in dentin-pulp regeneration. Recent studies have revealed that long noncoding RNAs (lncRNAs) are implicated in the osteogenic differentiation of DPSCs. However, the specific role and potential mechanisms of the lncRNA trihydroxyacetophenone domain containing nine antisense RNA 1 (THAP9-AS1) during osteogenic differentiation of DPSCs remain unknown. In the present study, we determined that THAP9-AS1 expression was upregulated during osteogenic differentiation of DPSCs. Moreover, we investigated the biological functions of THAP9-AS1 during osteogenic differentiation of DPSCs by loss-of-function assays. THAP9-AS1 knockdown inhibited osteogenic differentiation of DPSCs by decreasing alkaline phosphatase activity, alkaline phosphatase-positive cell ratio, mineralizing matrix and mRNA, and protein levels of early osteogenic-markers. We also found that THAP9-AS1 interacted with miR-652-3p, whose downstream gene target is vascular endothelial growth factor A (VEGFA). In addition, rescue assays indicated that VEGFA rescued the effects of THAP9-AS1 knockdown during osteogenic differentiation of DPSCs. In summary, we verified that knockdown of THAP9-AS1 inhibits osteogenic differentiation of DPSCs via the miR-652-3p/VEGFA axis. Our findings may be helpful to extend research on the mechanisms underlying osteogenic differentiation of DPSCs.

Cullin3 aggravates the inflammatory response of periodontal ligament stem cells via regulation of SHH signaling and Nrf2

It is found that the activation of Sonic Hedgehog (SHH) signaling pathway is related to the degree of inflammation in patients suffering from periodontitis. Cullin3 (CUL3), an important ubiquitin ligase, can control SHH signaling. In this study, we were dedicated to clarify the roles of SHH and CUL3 in P. gingivalis-LPS (Pg-LPS)-treated periodontal ligament stem cells (PDLSCs). In this study, cell viability was detected using cell counting kit-8 (CCK-8). The inflammatory cytokines of PDLSCs were estimated by enzyme-linked immunosorbent assay (ELISA). With the application of western blots, the protein levels of SHH, Gli1 and NF-E2-related factor 2 (Nrf2) were determined. Alkaline phosphatase staining and Alizarin red staining were performed to evaluate the differentiation and mineralization capabilities of PDLSCs. The apoptotic cells were screened using TUNEL staining. The results showed that Pg-LPS inhibited cell viability and triggered inflammation of PDLSCs. Overexpression of CUL3 weakened the differentiation and mineralization capabilities of PDLSCs. Moreover, CUL3 overexpression aggravated inflammation and cell apoptosis induced by Pg-LPS. It is worth noting that although the protein levels of SHH, Gli1 and Nrf2 were elevated in PDLSCs treated with Pg-LPS, overexpression of CUL3 decreased the expressions of Gli1 and Nrf2. Overall, SHH/Gli1 and Nrf2 were involved in the inflammation and cell apoptosis of PDLSCs, which was dominated by CUL3.

MicroRNAs: Harbingers and shapers of periodontal inflammation

Periodontal disease is an inflammatory reaction of the periodontal tissues to oral pathogens. In the present review we discuss the intricate effects of a regulatory network of gene expression modulators, microRNAs (miRNAs), as they affect periodontal morphology, function and gene expression during periodontal disease. These miRNAs are small RNAs involved in RNA silencing and post-transcriptional regulation and affect all stages of periodontal disease, from the earliest signs of gingivitis to the regulation of periodontal homeostasis and immunity and to the involvement in periodontal tissue destruction. MiRNAs coordinate periodontal disease progression not only directly but also through long non-coding RNAs (lncRNAs), which have been demonstrated to act as endogenous sponges or decoys that regulate the expression and function of miRNAs, and which in turn suppress the targeting of mRNAs involved in the inflammatory response, cell proliferation, migration and differentiation. While the integrity of miRNA function is essential for periodontal health and immunity, miRNA sequence variations (genetic polymorphisms) contribute toward an enhanced risk for periodontal disease progression and severity. Several polymorphisms in miRNA genes have been linked to an increased risk of periodontitis, and among those, miR-146a, miR-196, and miR-499 polymorphisms have been identified as risk factors for periodontal disease. The role of miRNAs in periodontal disease progression is not limited to the host tissues but also extends to the viruses that reside in periodontal lesions, such as herpesviruses (human herpesvirus, HHV). In advanced periodontal lesions, HHV infections result in the release of cytokines from periodontal tissues and impair antibacterial immune mechanisms that promote bacterial overgrowth. In turn, controlling the exacerbation of periodontal disease by minimizing the effect of periodontal HHV in periodontal lesions may provide novel avenues for therapeutic intervention. In summary, this review highlights multiple levels of miRNA-mediated control of periodontal disease progression, (i) through their role in periodontal inflammation and the dysregulation of homeostasis, (ii) as a regulatory target of lncRNAs, (iii) by contributing toward periodontal disease susceptibility through miRNA polymorphism, and (iv) as periodontal microflora modulators via viral miRNAs.

Periodontal ligament stem cells in the periodontitis niche: inseparable interactions and mechanisms

Periodontitis is characterized by the periodontium's pathologic destruction due to the host's overwhelmed inflammation to the dental plaque. The bacterial infections and subsequent host immune responses have shaped a distinct microenvironment, which generally affects resident periodontal ligament stem cells (PDLSCs). Interestingly, recent studies have revealed that impaired PDLSCs may also contribute to the disturbance of periodontal homeostasis. The putative vicious circle underlying the interesting "positive feedback" of PDLSCs in the periodontitis niche remains a hot research topic, whereas the inseparable interactions between resident PDLSCs and the periodontitis niche are still not fully understood. This review provides a microscopic view on the periodontitis progression, especially the quick but delicate immune responses to oral dysbacterial infections. We also summarize the interesting crosstalk of the resident PDLSCs with their surrounding periodontitis niche and potential mechanisms. Particularly, the microenvironment reduces the osteogenic properties of resident PDLSCs, which are closely related to their reparative activity. Reciprocally, these impaired PDLSCs may disrupt the microenvironment by aggravating the host immune responses, promoting aberrant angiogenesis, and facilitating the osteoclastic activity. We further recommend that more in-depth studies are required to elucidate the interactions of PDLSCs with the periodontal microenvironment and provide novel interventions for periodontitis.

Multidifferentiation potential of dental-derived stem cells

Tooth-related diseases and tooth loss are widespread and are a major public health issue. The loss of teeth can affect chewing, speech, appearance and even psychology. Therefore, the science of tooth regeneration has emerged, and attention has focused on tooth regeneration based on the principles of tooth development and stem cells combined with tissue engineering technology. As undifferentiated stem cells in normal tooth tissues, dental mesenchymal stem cells (DMSCs), which are a desirable source of autologous stem cells, play a significant role in tooth regeneration. Researchers hope to reconstruct the complete tooth tissues with normal functions and vascularization by utilizing the odontogenic differentiation potential of DMSCs. Moreover, DMSCs also have the ability to differentiate towards cells of other tissue types due to their multipotency. This review focuses on the multipotential capacity of DMSCs to differentiate into various tissues, such as bone, cartilage, tendon, vessels, neural tissues, muscle-like tissues, hepatic-like tissues, eye tissues and glands and the influence of various regulatory factors, such as non-coding RNAs, signaling pathways, inflammation, aging and exosomes, on the odontogenic/osteogenic differentiation of DMSCs in tooth regeneration. The application of DMSCs in regenerative medicine and tissue engineering will be improved if the differentiation characteristics of DMSCs can be fully utilized, and the factors that regulate their differentiation can be well controlled.

Analyses of key mRNAs and lncRNAs for different osteo-differentiation potentials of periodontal ligament stem cell and gingival mesenchymal stem cell

Both human periodontal ligament stem cells (hPDLSCs) and human gingival mesenchymal stem cells (hGMSCs) are candidate seed cells for bone tissue engineering, but the osteo-differentiation ability of the latter is weaker than the former, and the mechanisms are unknown. To explore the potential regulation of mRNAs and long non-coding RNAs (lncRNAs), this study obtained the gene expression profiles of hPDLSCs and hGMSCs in both undifferentiated and osteo-differentiated conditions by microarray assay and then analysed the common and specific differentially expressed mRNAs and lncRNAs in hPDLSCs and hGMSCs through bioinformatics method. The results showed that 275 mRNAs and 126 lncRNAs displayed similar changing patterns in hPDLSCs and hGMSCs after osteogenic induction, which may regulate the osteo-differentiation in both types of cells. In addition, the expression of 223 mRNAs and 238 lncRNAs altered only in hPDLSCs after osteogenic induction, and 177 mRNAs and 170 lncRNAs changed only in hGMSCs. These cell-specific differentially expressed mRNAs and lncRNAs could underlie the different osteo-differentiation potentials of hPDLSCs and hGMSCs. Finally, dickkopf Wnt signalling pathway inhibitor 1 (DKK1) was proved to be one regulator for the weaker osteo-differentiation ability of hGMSCs through validation experiments. We hope these results help to reveal new mRNAs-lncRNAs-based molecular mechanism for osteo-differentiation of hPDLSCs and hGMSCs and provide clues on strategies for improving stem cell-mediated bone regeneration.