MicroRNA let-7c-5p promotes osteogenic differentiation of dental pulp stem cells by inhibiting lipopolysaccharide-induced inflammation via HMGA2/PI3K/Akt signal blockade

Potential of Dental Pulp Stem Cell Exosomes: Unveiling miRNA-Driven Regenerative Mechanisms

Human dental pulp stem cells (hDPSCs) have emerged as a promising resource in regenerative medicine due to their unique ability to secrete exosomes containing a diverse array of bioactive molecules, particularly microRNAs (miRNAs). These exosomes appear to be essential for stimulating regenerative mechanisms, especially those associated with stem cell pluripotency and tissue repair. However, several challenges such as cargo specificity and delivery efficiency need to be addressed to maximise the therapeutic potential of hDPSC-derived exosomes and miRNA-based therapies. This narrative review explores hDPSCs' potential in regenerative medicine by examining their role in tissue engineering, secretome composition, exosome function, exosomal miRNA in diverse models, and miRNA profiling. Therefore, it is imperative to sustain ongoing research on miRNA to advance clinical applications in the field of regenerative medicine and dentistry. A comprehensive understanding of the specific miRNA composition within hDPSC-derived exosomes is essential to elucidate their mechanistic roles in diverse disease states and to inform the development of innovative therapeutic strategies. These findings hold significant potential for the development of innovative regenerative therapies and emphasises the importance of establishing a strong connection between translational research discoveries and clinical applications. hDPSC-derived exosomes and miRNA-based therapies play a crucial role in immune modulation, regenerative dentistry, and tissue repair.

Exosomal circFAM63Bsuppresses bone regeneration of postmenopausal osteoporosis via regulating miR-578/HMGA2 axis

Postmenopausal osteoporosis (PMOP) affects hundreds of millions of elderly women worldwide. The imbalance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption is the key factor in the progression of PMOP. Recently, exosomal circular RNAs have been considered as critical regulators in physiological and pathological progress. However, their roles in PMOP still require further exploration. Herein, we identified that the expression of exosomal circFAM63B significantly increased in PMOP patients and is closely related to bone density. We further demonstrated that circFAM63B inhibits osteogenic differentiation of bone marrow stromal cells and bone formation in ovariectomy mice by using a combination of in vitro and in vivo experiment strategies. Mechanistically, circFAM63B promotes HMGA2 expression by inhibiting miR-578, thereby suppressing bone repair. Our study proved that exosomal circFAM63B suppresses the bone regeneration of PMOP by regulating the miR-578/HMGA2 axis, which may provide new insights into the pathogenesis and development of PMOP. Knocking down exosomal circFAM63B could be regarded as a new strategy for the treatment of PMOP.

Elucidating epigenetic mechanisms governing odontogenic differentiation in dental pulp stem cells: an in-depth exploration

Epigenetics refers to the mechanisms such as DNA methylation and histone modification that influence gene expression without altering the DNA sequence. These epigenetic modifications can regulate gene transcription, splicing, and stability, thereby impacting cell differentiation, development, and disease occurrence. The formation of dentin is intrinsically linked to the odontogenic differentiation of dental pulp stem cells (DPSCs), which are recognized as the optimal cell source for dentin-pulp regeneration due to their varied odontogenic potential, strong proliferative and angiogenic characteristics, and ready accessibility Numerous studies have demonstrated the critical role of epigenetic regulation in DPSCs differentiation into specific cell types. This review thus provides a comprehensive review of the mechanisms by which epigenetic regulation controls the odontogenesis fate of DPSCs.

Effects of histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors on proliferative, differentiative, and regenerative functions of Toll-like receptor 2 (TLR-2)-stimulated human dental pulp cells (hDPCs)

OBJECTIVES

This in vitro study aimed to modify TLR-2-mediated effects on the paracrine, proliferative, and differentiation potentials of human dental pulp-derived cells using histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors.

MATERIALS AND METHODS

Cell viability was assessed using the XTT assay. Cells were either treated with 10 μg/ml Pam3CSK4 only, or pre-treated with valproic acid (VPA) (3 mM), trichostatin A (TSA) (3 μM), and MG-149 (3 μM) for a total of 4 h and 24 h. Control groups included unstimulated cells and cells incubated with inhibitors solvents only. Transcript levels for NANOG, OCT3-4, FGF-1 and 2, NGF, VEGF, COL-1A1, TLR-2, hβD-2 and 3, BMP-2, DSPP, and ALP were assessed through qPCR.

RESULTS

After 24 h, TSA pre-treatment significantly upregulated the defensins and maintained the elevated pro-inflammatory cytokines, but significantly reduced healing and differentiation genes. VPA significantly upregulated the pro-inflammatory cytokine levels, while MG-149 significantly downregulated them. Pluripotency genes were not significantly affected by any regimen.

CONCLUSIONS

At the attempted concentrations, TSA upregulated the defensins gene expression levels, and MG-149 exerted a remarkable anti-inflammatory effect; therefore, they could favorably impact the immunological profile of hDPCs.

CLINICAL RELEVANCE

Targeting hDPC nuclear function could be a promising option in the scope of the biological management of inflammatory pulp diseases.

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

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

Current concepts of microRNA-mediated regulatory mechanisms in human pulp tissue-derived stem cells: a snapshot in the regenerative dentistry

One of the most studied class of non-coding RNAs is microRNAs (miRNAs) which regulate more than 60% of human genes. A network of miRNA gene interactions participates in stem cell self-renewal, proliferation, migration, apoptosis, immunomodulation, and differentiation. Human pulp tissue-derived stem cells (PSCs) are an attractive source of dental mesenchymal stem cells (MSCs) which comprise human dental pulp stem cells (hDPSCs) obtained from the dental pulp of permanent teeth and stem cells isolated from exfoliated deciduous teeth (SHEDs) that would be a therapeutic opportunity in stomatognathic system reconstruction and repair of other damaged tissues. The regenerative capacity of hDPSCs and SHEDs is mediated by osteogenic, odontogenic, myogenic, neurogenic, angiogenic differentiation, and immunomodulatory function. Multi-lineage differentiation of PSCs can be induced or inhibited by the interaction of miRNAs with their target genes. Manipulating the expression of functional miRNAs in PSCs by mimicking miRNAs or inhibiting miRNAs emerged as a therapeutic tool in the clinical translation. However, the effectiveness and safety of miRNA-based therapeutics, besides higher stability, biocompatibility, less off-target effects, and immunologic reactions, have received particular attention. This review aimed to comprehensively overview the molecular mechanisms underlying miRNA-modified PSCs as a futuristic therapeutic option in regenerative dentistry.

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.

Application of Dental Pulp Stem Cells for Bone and Neural Tissue Regeneration in Oral and Maxillofacial Region

In the oral and maxillofacial region, the treatment of severe bone defects, caused by fractures, cancers, congenital abnormalities, etc., remains a great challenge. In addition, neurological disorders are frequently accompanied by these bone defects or the treatments for them. Therefore, novel bone regenerative techniques and methods to repair nerve injury are eagerly sought. Among them, strategies using dental pulp stem cells (DPSCs) are promising options. Human DPSCs can be collected easily from extracted teeth and are now considered a type of mesenchymal stem cell with higher clonogenic and proliferative potential. DPSCs have been getting attention as a cell source for bone and nerve regeneration. In this article, we reviewed the latest studies on osteogenic or neural differentiation of DPSCs as well as bone or neural regeneration methods using DPSCs and discussed the potential of DPSCs for bone and nerve tissue regeneration.

Comprehensive analysis of M2 macrophage-derived exosomes facilitating osteogenic differentiation of human periodontal ligament stem cells

BACKGROUND

The role of periodontal ligament stem cells (PDLSCs) and macrophage polarization in periodontal tissue regeneration and bone remodeling during orthodontic tooth movement (OTM) has been well documented. Nevertheless, the interactions between macrophages and PDLSCs in OTM remain to be investigated. Consequently, the present study was proposed to explore the effect of different polarization states of macrophages on the osteogenic differentiation of PDLSCs.

METHODS

After M0, M1 and M2 macrophage-derived exosomes (M0-exo, M1-exo and M2-exo) treatment of primary cultured human PDLSCs, respectively, mineralized nodules were observed by Alizarin red S staining, and the expression of ALP and OCN mRNA and protein were detected by RT-qPCR and Western blotting, correspondingly. Identification of differentially expressed microRNAs (DE-miRNA) in M0-exo and M2-exo by miRNA microarray, and GO and KEGG enrichment analysis of DE-miRNA targets, and construction of protein-protein interaction networks.

RESULTS

M2-exo augmented mineralized nodule formation and upregulated ALP and OCN expression in PDLSCs, while M0-exo had no significant effect. Compared to M0-exo, a total of 52 DE-miRNAs were identified in M2-exo. The expression of hsa-miR-6507-3p, hsa-miR-4731-3p, hsa-miR-4728-3p, hsa-miR-3614-5p and hsa-miR-6785-3p was significantly down-regulated, and the expression of hsa-miR-6085, hsa-miR-4800-5p, hsa-miR-4778-5p, hsa-miR-6780b-5p and hsa-miR-1227-5p was significantly up-regulated in M2-exo compared to M0-exo. GO and KEGG enrichment analysis revealed that the downstream targets of DE-miRNAs were mainly involved in the differentiation and migration of multiple cells.

CONCLUSIONS

In summary, we have indicated for the first time that M2-exo can promote osteogenic differentiation of human PDLSCs, and have revealed the functions and pathways involved in the DE-miRNAs of M0-exo and M2-exo and their downstream targets.

High-frequency repetitive transcranial magnetic stimulation (rTMS) protects against ischemic stroke by inhibiting M1 microglia polarization through let-7b-5p/HMGA2/NF-κB signaling pathway

Background

Microglia assume opposite phenotypes in response to ischemic brain injury, exerting neurotoxic and neuroprotective effects under different ischemic stages. Modulating M1/M2 polarization is a potential therapy for treating ischemic stroke. Repetitive transcranial magnetic stimulation (rTMS) held the capacity to regulate neuroinflammation and astrocytic polarization, but little is known about rTMS effects on microglia. Therefore, the present study aimed to examine the rTMS influence on microglia polarization and the underlying possible molecular mechanisms in ischemic stroke models.

Methods

Previously reported 10 Hz rTMS protocol that regulated astrocytic polarization was used to stimulate transient middle cerebral artery occlusion (MCAO) rats and oxygen and glucose deprivation/reoxygenation (OGD/R) injured BV2 cells. Specific expression levels of M1 marker iNOS and M2 marker CD206 were measured by western blotting and immunofluorescence. MicroRNA expression changes detected by high-throughput second-generation sequencing were validated by RT-PCR and fluorescence in situ hybridization (FISH) analysis. Dual-luciferase report assay and miRNA knock-down were applied to verify the possible mechanisms regulated by rTMS. Microglia culture medium (MCM) from different groups were collected to measure the TNF-α and IL-10 concentrations, and detect the influence on neuronal survival. Finally, TTC staining and modified Neurological Severity Score (mNSS) were used to determine the effects of MCM on ischemic stroke volume and neurological functions.

Results

The 10 Hz rTMS inhibited ischemia/reperfusion induced M1 microglia and significantly increased let-7b-5p level in microglia. HMGA2 was predicted and proved to be the target protein of let-7b-5p. HMGA2 and its downstream NF-κB signaling pathway were inhibited by rTMS. Microglia culture medium (MCM) collected from rTMS treated microglia contained lower TNF-α concentration but higher IL-10 concentration than no rTMS treated MCM, reducing ischemic volumes and neurological deficits of MCAO mice. However, knockdown of let-7b-5p by antagomir reversed rTMS effects on microglia phenotype and associated HMGA/NF-κB activation and neurological recovery.

Conclusion

High-frequency rTMS could alleviate ischemic stroke injury through inhibiting M1 microglia polarization via regulating let-7b-5p/HMGA2/NF-κB signaling pathway in MCAO models.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12868-022-00735-7.

Glycogen synthase kinase-3β inhibitor promotes the migration and osteogenic differentiation of rat dental pulp stem cells via the β-catenin/PI3K/Akt signaling pathway

Background/purpose

Glycogen synthase kinase-3β (GSK3β) inhibitor enhances bone formation, while dental pulp stem cells (DPSC) are potentially used to repair bone defects. The present study aimed to investigate the effect of AR-A014418 (AR, a specific glycogen synthase kinase-3β inhibitor) on the migration and osteogenic differentiation of rat-derived dental pulp stem cells (rDPSCs), and further explore the underlying mechanism.

Materials and methods

rDPSCs were isolated from rats, and then cultured with different concentrations of AR with or without LY294002 (a PI3K inhibitor). Then, cell viability, migration, osteogenic differentiation, and the involvement of PI3K pathway were detected by CCK-8 assay, Transwell assay, Alizarin Red S Staining, Alkaline phosphatase (ALP) assay, Western blot, and RT-PCR, respectively.

Results

Our present study demonstrated that AR of various concentrations (1 μM, 2.5 μM, and 5 μM) not only promoted the rDPSC proliferation and migration, but also increased calcium deposition, the activity of alkaline phosphatase (ALP), and levels of osteogenic markers (RUNX2, OPN, OCN, and OSX) in rDPSCs. It was also found that the administration of AR resulted in an increase in the expression level of p-GSK3β (Ser), β-catenin, p-PI3K, and p-Akt, and a reduction in p-GSK3β (Tyr216). Furthermore, PI3K inhibitor LY294002 abrogated the enhanced cell migration and osteogenic differentiation of rDPSCs induced by AR.

Conclusion

Our results provide evidence that AR significantly promotes migration and osteogenic differentiation of rDPSCs by activating β-catenin/PI3K/Akt signaling pathway.

Developmental venous anomalies are a genetic primer for cerebral cavernous malformations

Cerebral cavernous malformations (CCM) are a neurovascular anomaly that may occur sporadically, or be inherited due to autosomal dominant mutations in KRIT1 , CCM2 , or PDCD10 . Individual lesions are caused by somatic mutations which have been identified in KRIT1, CCM2, PDCD10, MAP3K3, and PIK3CA . However, the interactions between mutations, and their relative contributions to sporadic versus familial cases remain unclear. We show that mutations in KRIT1, CCM2, PDCD10, and MAP3K3 are mutually exclusive, but may co-occur with mutations in PIK3CA. We also find that MAP3K3 mutations may cause sporadic, but not familial CCM. Furthermore, we find identical PIK3CA mutations in CCMs and adjacent developmental venous anomalies (DVA), a common vascular malformation frequently found in the vicinity of sporadic CCMs. However, somatic mutations in MAP3K3 are found only in the CCM. This suggests that sporadic CCMs are derived from cells of the DVA which have acquired an additional mutation in MAP3K3 .

Therapeutic Potential of Synthetic Human β-Defensin 1 Short Motif Pep-B on Lipopolysaccharide-Stimulated Human Dental Pulp Stem Cells

Dental pulp inflammation is a widespread public problem usually caused by caries or trauma. Alleviating inflammation is critical to inflamed pulp repair. Human β-defensin 1 short motif Pep-B is a cationic peptide that has anti-inflammatory, antibacterial, and immunoregulation properties, but its repair effect on human dental pulp stem cells (hDPSCs) under inflammation remains unclear. In this study, we aimed to investigate anti-inflammatory function of Pep-B and explore its therapeutic potential in lipopolysaccharide-(LPS-) induced hDPSCs. CCK-8 assay and transwell assay evaluated effects of Pep-B on hDPSC proliferation and chemotaxis. Inflammatory response in hDPSCs was induced by LPS; after Pep-B application, lactate dehydrogenase release, intracellular ROS, inflammatory factor genes expression and possible signaling pathway were measured. Then, osteo-/odontoblast differentiation effect of Pep-B on LPS-induced hDPSCs was detected. The results showed that Pep-B promoted hDPSC proliferation and reduced LPS-induced proinflammatory marker expression, and western blot result indicated that Pep-B inhibited inflammatory activation mediated by NF-κB and MAPK pathways. Pep-B also enhanced the expression of the osteo-/odontogenic genes and proteins, alkaline phosphatase activity, and nodule mineralization in LPS-stimulated hDPSCs. These findings indicate that Pep-B has anti-inflammatory activity and promote osteo-/odontoblastic differentiation in LPS-induced inflammatory environment and may have a potential role of hDPSCs for repair and regeneration.

Toll-Like Receptors and Dental Mesenchymal Stromal Cells

Dental mesenchymal stromal cells (MSCs) are a promising tool for clinical application in and beyond dentistry. These cells possess multilineage differentiation potential and immunomodulatory properties. Due to their localization in the oral cavity, these cells could sometimes be exposed to different bacteria and viruses. Dental MSCs express various Toll-like receptors (TLRs), and therefore, they can recognize different microorganisms. The engagement of TLRs in dental MSCs by various ligands might change their properties and function. The differentiation capacity of dental MSCs might be either inhibited or enhanced by TLRs ligands depending on their nature and concentrations. Activation of TLR signaling in dental MSCs induces the production of proinflammatory mediators. Additionally, TLR ligands alter the immunomodulatory ability of dental MSCs, but this aspect is still poorly explored. Understanding the role of TLR signaling in dental MSCs physiology is essential to assess their role in oral homeostasis, inflammatory diseases, and tissue regeneration.

Role of Lipopolysaccharide, Derived from Various Bacterial Species, in Pulpitis—A Systematic Review

Lipopolysaccharide (LPS) is widely used for induction of inflammation in various human tissues, including dental pulp. The purpose of this study was to summarize current medical literature focusing on (1) cell types used by researchers to simulate dental pulp inflammation, (2) LPS variants utilized in experimental settings and how these choices affect the findings. Our study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We searched for studies reporting outcomes of lipopolysaccharide application on dental pulp cells in vitro using electronic databases: MEDLINE, Web of Science and Scopus. Having gathered data from 115 papers, we aimed to present all known effects LPS has on different cell types present in dental pulp. We focused on specific receptors and particles that are involved in molecular pathways. Our review provides an essential foundation for further research using in vitro models of pulpitis.

Increased Expression of miR-7a-5p and miR-592 during Expansion of Rat Dental Pulp Stem Cells and Their Implication in Osteogenic Differentiation

Dental pulp stem cells (DPSCs) possess strong osteogenic differentiation potential and are promising cell sources in regenerative medicine. However, such differentiation capacity progressively declines during their in vitro expansion. MicroRNAs (miRNAs) play important roles in modulating stem cell differentiation. This study aimed (1) to determine if miR-7a-5p and miR-592 are involved in maintaining and regulating osteogenic differentiation of DPSCs, and (2) to explore their potential regulatory pathways. We found that the expression of miR-7a-5p and miR-592 was significantly upregulated during the expansion of rat DPSCs (rDPSCs). Overexpression of these miRNAs inhibited the osteogenic/odontogenic differentiation of rDPSCs, as evidenced by calcium deposition and osteogenic/odontogenic gene expression. RT-qPCR determined that miR-592 could downregulate heat shock protein B8, whose expression is reduced during the expansion of rDPSCs. Furthermore, RNA-seq and bioinformatics analysis identified significant signaling pathways of miR-7a-5p and miR-592 in regulating osteogenic differentiation, including TNF, MAPK, and PI3K-Akt pathways. We conclude that upregulating miR-7a-5p and miR-592 suppresses the osteogenic differentiation of rDPSCs during their in vitro expansion, likely via TNF, MAPK, and PI3K-Akt pathways. The results may shed light on application of miR-7a-5p and miR-592 for maintaining osteo-differentiation potential in stem cells for bone regeneration and bone-related disease treatment.

MicroRNA let-7f alleviates vascular endothelial cell dysfunction via targeting HMGA2 under oxygen-glucose deprivation and reoxygenation

Stroke is a fatal disease with high disability and mortality and there is no credible treatment for stroke at present. Studies on stroke are extensively developed to explore the underlying mechanisms of ischemic and reperfusion injuries. Herein, we investigated the functions of microRNA let-7f (also termed let-7f-5p) in vascular endothelial cell dysfunction. The bEnd.3 cells were stimulated with oxygen-glucose deprivation and reoxygenation (OGD/R) to mimic cell injury in vitro. CCK-8 assays, flow cytometry and western blot analyses were conducted to examine the viability and apoptosis of bEnd.3 cells. Reverse transcription quantitative polymerase chain reaction analyses were employed to measure RNA expression. Endothelial cell permeability in vitro assay was employed to assess endothelial permeability of bEnd.3 cells, and expression levels of proteins associated with cell apoptosis or blood-brain barrier (BBB) were detected by western blot analyses. Luciferase reporter assay was conducted to explore the combination between let-7f and HMGA2. We found that OGD/R induced injuries on endothelial cells (bEnd.3) by decreasing cell viability and promoting cell apoptosis. Let-7f exhibited low expression in bEnd.3 cells under OGD/R. Let-7f overexpression increased the viability of bEnd.3 cells and inhibited cell apoptosis. In addition, the endothelial permeability of bEnd.3 cells was increased by OGD/R and reversed by let-7f overexpression. The levels of tight junction proteins (ZO-1 and occludin) were downregulated by OGD/R and then reversed by let-7f overexpression. Mechanistically, HMGA2 is a target gene of let-7f and its expression was negatively regulated by let-7f. Rescue assays revealed that HMGA2 overexpression reversed the effects of let-7f overexpression on cell viability, cell apoptosis, endothelial permeability, and BBB function. In conclusion, let-7f alleviates vascular endothelial cell dysfunction by downregulating HMGA2 expression under OGD/R.

Epigenetic regulation of dental pulp stem cells and its potential in regenerative endodontics

Regenerative endodontics (RE) therapy means physiologically replacing damaged pulp tissue and regaining functional dentin–pulp complex. Current clinical RE procedures recruit endogenous stem cells from the apical papilla, periodontal tissue, bone marrow and peripheral blood, with or without application of scaffolds and growth factors in the root canal space, resulting in cementum-like and bone-like tissue formation. Without the involvement of dental pulp stem cells (DPSCs), it is unlikely that functional pulp regeneration can be achieved, even though acceptable repair can be acquired. DPSCs, due to their specific odontogenic potential, high proliferation, neurovascular property, and easy accessibility, are considered as the most eligible cell source for dentin–pulp regeneration. The regenerative potential of DPSCs has been demonstrated by recent clinical progress. DPSC transplantation following pulpectomy has successfully reconstructed neurovascularized pulp that simulates the physiological structure of natural pulp. The self-renewal, proliferation, and odontogenic differentiation of DPSCs are under the control of a cascade of transcription factors. Over recent decades, epigenetic modulations implicating histone modifications, DNA methylation, and noncoding (nc)RNAs have manifested as a new layer of gene regulation. These modulations exhibit a profound effect on the cellular activities of DPSCs. In this review, we offer an overview about epigenetic regulation of the fate of DPSCs; in particular, on the proliferation, odontogenic differentiation, angiogenesis, and neurogenesis. We emphasize recent discoveries of epigenetic molecules that can alter DPSC status and promote pulp regeneration through manipulation over epigenetic profiles.

lncRNA HHIP-AS1 Promotes the Osteogenic Differentiation Potential and Inhibits the Migration Ability of Periodontal Ligament Stem Cells

Alveolar bone remodeling under orthodontic force is achieved by periodontal ligament stem cells (PDLSCs), which are sensitive to mechanical loading. How to regulate functions of PDLSCs is a key issue in bone remodeling during orthodontic tooth movement. This study is aimed at investigating the roles of lncRNA Hedgehog-interacting protein antisense RNA 1 (HHIP-AS1) in the functional regulation of PDLSCs. First, HHIP-AS1 expression was downregulated in PDLSCs under continuous compressive pressure. Then, we found that the alkaline phosphatase activity, in vitro mineralization, and expression levels of bone sialoprotein, osteocalcin, and osterix were increased in PDLSCs by HHIP-AS1. The results of scratch migration and transwell chemotaxis assays revealed that HHIP-AS1 inhibited the migration and chemotaxis abilities of PDLSCs. In addition, the RNA sequencing data showed that 356 mRNAs and 14 lncRNAs were upregulated, including receptor tyrosine kinase-like orphan receptor 2 and nuclear-enriched abundant transcript 1, while 185 mRNAs and 6 lncRNAs were downregulated, including fibroblast growth factor 5 and LINC00973, in HHIP-AS1-depleted PDLSCs. Bioinformatic analysis revealed several biological processes and signaling pathways related to HHIP-AS1 functions, including the PI3K-Akt signaling pathway and JAK-STAT signaling pathway. In conclusion, our findings indicated that HHIP-AS1 was downregulated in PDLSCs under compressive pressure, and it promoted the osteogenic differentiation potential and inhibited the migration and chemotaxis abilities of PDLSCs. Thus, HHIP-AS1 may be a potential target for accelerating tooth movement during orthodontic treatment.

The Role of microRNAs in Pulp Inflammation

The dental pulp can be affected by thermal, physical, chemical, and bacterial phenomena that stimulate the inflammatory response. The pulp tissue produces an immunological, cellular, and vascular reaction in an attempt to defend itself and resolve the affected tissue. The expression of different microRNAs during pulp inflammation has been previously documented. MicroRNAs (miRNAs) are endogenous small molecules involved in the transcription of genes that regulate the immune system and the inflammatory response. They are present in cellular and physiological functions, as well as in the pathogenesis of human diseases, becoming potential biomarkers for diagnosis, prognosis, monitoring, and safety. Previous studies have evidenced the different roles played by miRNAs in proinflammatory, anti-inflammatory, and immunological phenomena in the dental pulp, highlighting specific key functions of pulp pathology. This systematized review aims to provide an understanding of the role of the different microRNAs detected in the pulp and their effects on the expression of the different target genes that are involved during pulp inflammation.

Mesenchymal Stem Cell-Derived Exosomes Induced by IL-1β Attenuate Urethral Stricture Through Let-7c/PAK1/NF-κB-Regulated Macrophage M2 Polarization

Background

Urethral stricture is a clinical challenge for both patients and clinicians. Post-traumatic urethral stricture is associated with formation of scar tissue caused by excessive inflammation. The aim of this study is exploring potential therapeutic strategies for this condition.

Methods

In vivo experiments on New Zealand rabbits and in vitro experiments on THP-1 monocytes and urethral fibroblasts were performed to investigate the effects on post-traumatic urethral stricture of exosomes isolated from IL-1β-treated mesenchymal stem cells (Exo-MSCs^IL-1β) and the role of macrophage M2 polarization in this process. Additionally, related signaling and mechanism behind were explored.

Results

In a New Zealand rabbit model of post-traumatic urethral stricture, injection of Exo-MSCs^IL-1β significantly reduced urethral stricture and collagen fiber accumulation compared with Exo-MSCs. Addition of Exo-MSCs^IL-1β to THP-1 monocytes in vitro induced M2 macrophage polarization, which, in turn, inhibited activation of urethral fibroblasts and synthesis of collagen. Mechanistically, Exo-MSCs^IL-1β were found to contain high levels of the microRNA let-7c, and luciferase reporter assays showed that let-7c interacted with the 3'UTR of PAK1 mRNA. Transfection of THP-1 cells with a let-7c mimic downregulated PAK1 expression and inhibited activation of the NF-κB signaling pathway.

Conclusion

These results support a role for let-7c-containing Exo-MSCs^IL-1β in reducing urethral stricture via inhibition of PAK1-NF-κB signaling, M2 macrophage polarization, and differentiation of urethral myofibroblasts.

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.

MiR-26a inhibits the inflammatory response of microglia by targeting HMGA2 in intracerebral hemorrhage

Objective

Intracerebral hemorrhage (ICH) is a common cerebrovascular disease with high mortality and poor prognosis. Therefore, the biological function and underlying molecular mechanism of miR-26a in inflammatory injury following ICH was investigated.

Methods

The potential role of miR-26a was investigated in lipopolysaccharide (LPS)-treated microglial cells by quantitative real-time PCR. To explore the potential role of HMGA2 in the miR-26a-regulated inflammatory response, LPS-induced microglial cells were cotransfected with an miR-26a mimic and pcDNA-HMGA2. Then, lentivirus-mediated overexpression of an miR-26a mimic in mouse microglial cells was performed, and the effects of miR-26a treatment on IL-6, IL-1β, and TNF-α expression in the mouse brain, neurological behavior, and rotarod test performance of mice after ICH were observed.

Results

MiR-26a was significantly downregulated in LPS-treated microglia and ICH mouse models. MiR-26a markedly reduced IL-6, IL-1β, and TNF-α expression in LPS-treated microglial cells. Furthermore, HMGA2 was verified as a direct target of miR-26a. In vivo, miR-26a overexpression in mouse microglial cells significantly suppressed proinflammatory cytokine expression in mouse brains and markedly improved the neurological behavior and rotarod test performance of mice after ICH.

Conclusion

MiR-26a remarkably inhibited proinflammatory cytokine release by targeting HMGA2, indicating that miR-26a could protect against secondary brain injury following ICH.

Microenvironment Influences Odontogenic Mesenchymal Stem Cells Mediated Dental Pulp Regeneration

Dental pulp as a source of nutrition for the whole tooth is vulnerable to trauma and bacterial invasion, which causes irreversible pulpitis and pulp necrosis. Dental pulp regeneration is a valuable method of restoring the viability of the dental pulp and even the whole tooth. Odontogenic mesenchymal stem cells (MSCs) residing in the dental pulp environment have been widely used in dental pulp regeneration because of their immense potential to regenerate pulp-like tissue. Furthermore, the regenerative abilities of odontogenic MSCs are easily affected by the microenvironment in which they reside. The natural environment of the dental pulp has been proven to be capable of regulating odontogenic MSC homeostasis, proliferation, and differentiation. Therefore, various approaches have been applied to mimic the natural dental pulp environment to optimize the efficacy of pulp regeneration. In addition, odontogenic MSC aggregates/spheroids similar to the natural dental pulp environment have been shown to regenerate well-organized dental pulp both in preclinical and clinical trials. In this review, we summarize recent progress in odontogenic MSC-mediated pulp regeneration and focus on the effect of the microenvironment surrounding odontogenic MSCs in the achievement of dental pulp regeneration.

The molecular functions of Biodentine and mineral trioxide aggregate in lipopolysaccharide-induced inflamed dental pulp cells

AIM

To explore the proliferation, adhesion and differentiation response and the underlying mechanisms that occur in lipopolysaccharide (LPS)-induced inflamed dental pulp cells (DPCs) in contact with Biodentine and mineral trioxide aggregate (MTA).

METHODOLOGY

The DPCs were isolated from three healthy donors and named DPC-H1 to DPC-H3. The DPCs were pre-cultured with 2 or 5 μg mL^-1 LPS for 24 h to induce inflammation. The expression of inflammation marker miR-146a was detected by q-PCR. The normal and LPS-induced DPCs were further treated with 0.14 mg mL^-1 Biodentine or 0.13 mg mL^-1 MTA for 24 h. MTT assay and adhesion assay were used to analyse the changes of cell phenotypes. DSPP, AKT and ERK expressions were detected by Western blotting. The data were analysed by Mann-Whitney test or two-way anova. Differences were considered statistically significant when P < 0.05.

RESULTS

In LPS-induced DPCs, Biodentine and MTA treatment neither induced nor aggravated LPS-induced inflammation, but their presence did increase the expression of the odontogenic differentiation marker DSPP. Under 2 or 5 μg mL^-1 LPS-induced inflammation, Biodentine and MTA promoted the proliferation of DPC cells, and significantly in DPC-H2 (P < 0.0001 for both reagents). With the treatment of 2 μg mL^-1 LPS, the cell adhesion of DPCs on the fibronectin-coated culture plates was increased significantly by Biodentine (P = 0.0413) and MTA (P < 0.0001). Biodentine and MTA regulated cell adhesion on the fibronectin-coated culture plates (P < 0.0001 for both reagents) and proliferation (P < 0.0001 for both reagents) via the AKT pathway. However, the AKT pathway was not involved in the expression of DSPP induced by Biodentine and MTA.

CONCLUSION

Biodentine and MTA enhanced the proliferation, adhesion and differentiation of LPS-induced DPCs. The proliferation and adhesion process induced by Biodentine and MTA was via the AKT pathway. However, the cellular differentiation process might not use the same pathway, and this needs to be explored in future studies.

Dynamic proteomic profiling of human periodontal ligament stem cells during osteogenic differentiation

Background

Human periodontal ligament stem cells (hPDLSCs) are ideal seed cells for periodontal regeneration. A greater understanding of the dynamic protein profiles during osteogenic differentiation contributed to the improvement of periodontal regeneration tissue engineering.

Methods

Tandem Mass Tag quantitative proteomics was utilized to reveal the temporal protein expression pattern during osteogenic differentiation of hPDLSCs on days 0, 3, 7 and 14. Differentially expressed proteins (DEPs) were clustered and functional annotated by Gene Ontology (GO) terms. Pathway enrichment analysis was performed based on the Kyoto Encyclopedia of Genes and Genomes database, followed by the predicted activation using Ingenuity Pathway Analysis software. Interaction networks of redox-sensitive signalling pathways and oxidative phosphorylation (OXPHOS) were conducted and the hub protein SOD2 was validated with western blotting.

Results

A total of 1024 DEPs were identified and clustered in 5 distinctive clusters representing dynamic tendencies. The GO enrichment results indicated that proteins with different tendencies show different functions. Pathway enrichment analysis found that OXPHOS was significantly involved, which further predicted continuous activation. Redox-sensitive signalling pathways with dynamic activation status showed associations with OXPHOS to various degrees, especially the sirtuin signalling pathway. SOD2, an important component of the sirtuin pathway, displays a persistent increase during osteogenesis. Data are available via ProteomeXchange with identifier PXD020908.

Conclusion

This is the first in-depth dynamic proteomic analysis of osteogenic differentiation of hPDLSCs. It demonstrated a dynamic regulatory mechanism of hPDLSC osteogenesis and might provide a new perspective for research on periodontal regeneration.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-020-02123-6.

MicroRNA-497-5p stimulates osteoblast differentiation through HMGA2-mediated JNK signaling pathway

Background

Osteoporosis (OP) has the characteristics of the decline in bone mineral density and worsening of bone quality, contributing to a higher risk of fractures. Some microRNAs (miRNAs) have been validated as possible mediators of osteoblast differentiation. We herein aimed to clarify whether miR-497-5p regulates the differentiation of osteoblasts in MC3T3-E1 cells.

Methods

The expression of miR-497-5p in OP patients and controls was measured by RT-qPCR, and its expression changes during osteoblast differentiation were determined as well. The effects of miR-497-5p on the differentiation of MC3T3-E1 cells were studied using MTT, ALR staining, and ARS staining. The target gene of miR-497-5p was predicted by TargetScan, and the effects of its target gene on differentiation and the pathway involved were investigated.

Results

miR-497-5p expressed poorly in OP patients, and its expression was upregulated during MC3T3-E1 cell differentiation. Overexpression of miR-497-5p promoted mineralized nodule formation and the expression of RUNX2 and OCN. miR-497-5p targeted high mobility group AT-Hook 2 (HMGA2), while the upregulation of HMGA2 inhibited osteogenesis induced by miR-497-5p mimic. miR-497-5p significantly impaired the c-Jun NH2-terminal kinase (JNK) pathway, whereas HMGA2 activated this pathway. Activation of the JNK pathway inhibited the stimulative role of miR-497-5p mimic in osteogenesis.

Conclusions

miR-497-5p inhibits the development of OP by promoting osteogenesis via targeting HMGA2.

Epigenetic Regulation of Dental Pulp Stem Cell Fate

Epigenetic regulation, mainly involving DNA methylation, histone modification, and noncoding RNAs, affects gene expression without modifying the primary DNA sequence and modulates cell fate. Mesenchymal stem cells derived from dental pulp, also called dental pulp stem cells (DPSCs), exhibit multipotent differentiation capacity and can promote various biological processes, including odontogenesis, osteogenesis, angiogenesis, myogenesis, and chondrogenesis. Over the past decades, increased attention has been attracted by the use of DPSCs in the field of regenerative medicine. According to a series of studies, epigenetic regulation is essential for DPSCs to differentiate into specialized cells. In this review, we summarize the mechanisms involved in the epigenetic regulation of the fate of DPSCs.