Nuclear factor-κB modulates osteogenesis of periodontal ligament stem cells through competition with β-catenin signaling in inflammatory microenvironments

Anti-inflammatory effects of shikonin in human periodontal ligament cells

CONTEXT

Shikonin (SHI), an active component extracted from Radix Arnebiae, has been reported to possess anti-inflammatory properties in various cells. However, its effect on lipopolysaccharide (LPS)-stimulated human periodontal ligament cells (hPDLCs) is unknown.

OBJECTIVE

To investigate the effects of SHI on the expression of inflammatory related cytokines in LPS-stimulated hPDLCs.

MATERIALS AND METHODS

The effects of SHI (0.125, 0.25, 0.5, 1, and 2 μg/mL) on hPDLCs proliferation for 1, 3 and 7 days were measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The expression of interleukin-1 (IL-1), IL-6, tumor necrosis factor-α (TNF-α), matrix metalloproteinase-2 (MMP-2), MMP-9 and cyclooxygenase-2 (COX-2) were detected in hPDLCs following SHI treatment (0.25 and 0.5 μg/mL) using Quantitative Reverse Transcriptase Polymerase Chain Reaction (qRT-PCR). The signaling pathways triggered by SHI in hPDLC were evaluated using western blotting.

RESULTS

LD50 of SHI is 1.7 μg/mL (day 1) and 1.1 μg/mL (day 3 and 7) in hPDLCs. No morphological changes were observed when hPDLCs were treated with LPS only (1 μg/mL) or LPS with SHI (0.25 and 0.5 μg/mL). Data from qRT-PCR suggests that SHI attenuates LPS-induced increases of IL-1, IL-6, TNF-α, MMP-2, MMP-9 and COX-2 in hPDLCs. Down-regulation of phosphorylated extracellular signal-regulated kinase (ERK) and nuclear factor-κB (NF-κB), and up-regulation of I-κB, were observed in LPS-stimulated hPDLCs after exposed to SHI at 0.25 or 0.5 μg/mL.

DISCUSSION AND CONCLUSIONS

SHI possesses anti-inflammatory effects in LPS-stimulated hPDLCs via phospho-ERK and NF-κB/I-κB signaling pathways; this suggests that SHI may hold potential as an anti-inflammatory agent against periodontitis.

Autophagy in the dentin-pulp complex against inflammation

The dentin-pulp complex is a highly specialized tissue for protecting the dental pulp. Odontoblasts are long-lived, hard-tissue-forming cells in the dentin-pulp complex and critically involved in inflammatory responses against invading pathogens. Autophagy is a highly conserved homeostasis mechanism of living cells under various stress conditions. Growing evidence in the literature addresses the role of autophagy in odontoblast differentiation and aging. This review summarizes the current knowledge about autophagy for the dentin-pulp complex in resisting inflammation.

Resveratrol enhances the functionality and improves the regeneration of mesenchymal stem cell aggregates

Mesenchymal stem cell (MSC)-based regeneration, specifically cell aggregate or cell sheet engineering, is a promising approach for tissue reconstruction. Considering the advantages of ease of harvest and lack of immune rejection, the application of autologous MSCs (i.e., patients' own MSCs) in regenerative medicine has developed considerable interest. However, the impaired cell viability and regenerative potential following MSCs impacted by disease remain a major challenge. Resveratrol (RSV) exhibits reliable and extensive rejuvenative activities that have received increasing clinical attention. Here, we uncovered that resveratrol enhances the functionality and improves the regeneration of mesenchymal stem cell aggregates. Periodontal ligament MSCs (PDLSCs) from normal control subjects (N-PDLSCs) and periodontitis patients (P-PDLSCs) were investigated. Compared to N-PDLSCs, P-PDLSCs were less capable of forming cell aggregates, and P-PDLSC aggregates showed impaired osteogenesis and regeneration. These functional declines could be mimicked in N-PDLSCs by tumor necrosis factor alpha (TNF-α) treatment. Notably, a TNF-α-induced functional decline in N-PDLSC aggregates was rescued by RSV application. More importantly, in both N-PDLSCs and P-PDLSCs, RSV promoted cell aggregate formation and improved their osteogenic potential. Furthermore, as proven ectopically in vivo, the tissue regenerative capability of P-PDLSC aggregates was also enhanced after RSV treatment during aggregate formation in vitro. Finally, in a rat in situ regeneration model, we successfully applied both N-PDLSC aggregates and P-PDLSC aggregates to repair periodontal defects upon long-term functional improvements by RSV preconditioning. Together, our data unravel a novel methodology for using pharmacology (i.e., RSV)-based cell aggregate engineering to improve the functionality and facilitate the regeneration of MSCs from both healthy and inflammatory microenvironments, shedding light on improving the application of autologous MSC-mediated regenerative medicine.

Resveratrol counteracts bone loss via mitofilin-mediated osteogenic improvement of mesenchymal stem cells in senescence-accelerated mice

Rational: Senescence of mesenchymal stem cells (MSCs) and the related functional decline of osteogenesis have emerged as the critical pathogenesis of osteoporosis in aging. Resveratrol (RESV), a small molecular compound that safely mimics the effects of dietary restriction, has been well documented to extend lifespan in lower organisms and improve health in aging rodents. However, whether RESV promotes function of senescent stem cells in alleviating age-related phenotypes remains largely unknown. Here, we intend to investigate whether RESV counteracts senescence-associated bone loss via osteogenic improvement of MSCs and the underlying mechanism.

Methods: MSCs derived from bone marrow (BMMSCs) and the bone-specific, senescence-accelerated, osteoblastogenesis/osteogenesis-defective mice (the SAMP6 strain) were used as experimental models. In vivo application of RESV was performed at 100 mg/kg intraperitoneally once every other day for 2 months, and in vitro application of RESV was performed at 10 μM. Bone mass, bone formation rates and osteogenic differentiation of BMMSCs were primarily evaluated. Metabolic statuses of BMMSCs and the mitochondrial activity, transcription and morphology were also examined. Mitofilin expression was assessed at both mRNA and protein levels, and short hairpin RNA (shRNA)-based gene knockdown was applied for mechanistic experiments.

Results: Chronic intermittent application of RESV enhances bone formation and counteracts accelerated bone loss, with RESV improving osteogenic differentiation of senescent BMMSCs. Furthermore, in rescuing osteogenic decline under BMMSC senescence, RESV restores cellular metabolism through mitochondrial functional recovery via facilitating mitochondrial autonomous gene transcription. Molecularly, in alleviating senescence-associated mitochondrial disorders of BMMSCs, particularly the mitochondrial morphological alterations, RESV upregulates Mitofilin, also known as inner membrane protein of mitochondria (Immt) or Mic60, which is the core component of the mitochondrial contact site and cristae organizing system (MICOS). Moreover, Mitofilin is revealed to be indispensable for mitochondrial homeostasis and osteogenesis of BMMSCs, and that insufficiency of Mitofilin leads to BMMSC senescence and bone loss. More importantly, Mitofilin mediates resveratrol-induced mitochondrial and osteogenic improvements of BMMSCs in senescence.

Conclusion: Our findings uncover osteogenic functional improvements of senescent MSCs as critical impacts in anti-osteoporotic practice of RESV, and unravel Mitofilin as a novel mechanism mediating RESV promotion on mitochondrial function in stem cell senescence.

Mechanical stretch-induced osteogenic differentiation of human jaw bone marrow mesenchymal stem cells (hJBMMSCs) via inhibition of the NF-κB pathway

Severe malocclusion can contribute to several serious dental and physical conditions, such as digestive difficulties, periodontal disease, and severe tooth decay. Orthodontic treatment is mainly used to treat malocclusion. Forces in orthodontic tooth results in bone resorption on the pressure side and bone deposition on the tension side. Osteoblasts have been considered as the key component in bone regeneration on the tension side. However, the underlying mechanisms remain unclear. In this study, we focus on how mechanical stretch regulates the osteogenesis during orthodontic treatment. Human jaw bone marrow mesenchymal stem cells (hJBMMSCs) were isolated from healthy adult donors and cultured in regular medium (control) or osteogenic medium (OS). Under OS culture, hJBMMSCs presented osteogenic differentiation potentials, as evidenced by increased mineralization, enhanced calcium deposition, and upregulated expression of osteogenesis markers (ALP, osterix, and Runx). What's more, the OS-induced osteogenesis of hJBMMSCs is associated with the dephosphorylation of IKK, activation of IKBα, and phosphorylation/nucleic accumulation of P65, which all indicated the inhibition of NF-κB activity. Overexpressing P65 in hJBMMSCs, which could constantly activate NF-κB, prevented the osteogenic differentiation in the OS. After that, we applied the Flexcell tension system, which could cause mechanical stretch on cultured hJBMMSCs to mimic the tension forces during tooth movement. Mechanical stretch resulted in 3.5-fold increase of ALP activity and 2.4-fold increase of calcium deposition after 7 days and 21 days treatment, respectively. The expression levels of ALP, Run×2, and Osterix were also significantly upregulated. In the meantime, applying mechanical stretch on OS-cultured hJBMMSCs also dramatically promoted the OS-induced osteogenesis. Both OS and mechanical stretch downregulated NF-κB activity. By overexpressing P65 in hJBMMSCs, neither OS nor mechanical stretch could induce their osteogenesis. These results indicated that, like OS induction, mechanical stretch-facilitated osteogenesis of hJBMMSCs by inhibiting NF-κB in the noninflammatory environments.

Tension force-induced bone formation in orthodontic tooth movement via modulation of the GSK-3β/β-catenin signaling pathway

Orthodontic force-induced osteogenic differentiation and bone formation at tension sites play a critical role in orthodontic tooth movement. However, the molecular mechanism underlying this phenomenon is poorly understood. In the current study, we investigated the involvement of the GSK-3β/β-catenin signaling pathway, which is critical for bone formation during tooth movement. We established a rat tooth movement model to test the hypothesis that orthodontic force may stimulate bone formation at the tension site of the moved tooth and promote the rate of tooth movement via regulation of the GSK-3β/β-catenin signaling pathway. Our results showed that continued mechanical loading increased the distance between the first and second molar in rats. In addition, the loading force increased bone formation at the tension site, and also increased phospho-Ser9-GSK-3β expression and β-catenin signaling pathway activity. Downregulation of GSK-3β activity further increased bone parameters, including bone mineral density, bone volume to tissue volume and trabecular thickness, as well as ALP- and osterix-positive cells at tension sites during tooth movement. However, ICG-001, the β-catenin selective inhibitor, reversed the positive effects of GSK-3β inhibition. In addition, pharmaceutical inhibition of GSK-3β or local treatment with β-catenin inhibitor did not influence the rate of tooth movement. Based on these results, we concluded that GSK-3β/β-catenin signaling contributes to the bone remodeling induced by orthodontic forces, and can be used as a potential therapeutic target in clinical dentistry.

Expression and regulation of long noncoding RNAs during the osteogenic differentiation of periodontal ligament stem cells in the inflammatory microenvironment

Although long noncoding RNAs (lncRNAs) have been emerging as critical regulators in various tissues and biological processes, little is known about their expression and regulation during the osteogenic differentiation of periodontal ligament stem cells (PDLSCs) in inflammatory microenvironment. In this study, we have identified 63 lncRNAs that are not annotated in previous database. These novel lncRNAs were not randomly located in the genome but preferentially located near protein-coding genes related to particular functions and diseases, such as stem cell maintenance and differentiation, development disorders and inflammatory diseases. Moreover, we have identified 650 differentially expressed lncRNAs among different subsets of PDLSCs. Pathway enrichment analysis for neighboring protein-coding genes of these differentially expressed lncRNAs revealed stem cell differentiation related functions. Many of these differentially expressed lncRNAs function as competing endogenous RNAs that regulate protein-coding transcripts through competing shared miRNAs.

Tumor necrosis factor-alpha inhibits osteogenic differentiation of pre-osteoblasts by downregulation of EphB4 signaling via activated nuclear factor-kappaB signaling pathway

BACKGROUND AND OBJECTIVE

The majority of experiments show that tumor necrosis factor-alpha (TNF-α) inhibits osteogenic differentiation of mesenchymal stem cells and pre-osteoblasts by activated nuclear factor-kappaB (NF-κB) signaling. However, the underlying mechanisms by which NF-κB signaling inhibits osteogenic differentiation are not fully understood. The aim of the present study was to investigate whether EphB4 signaling inhibition mediates the effects of TNF-α-activated NF-κB signaling on osteogenic differentiation of pre-osteoblasts.

MATERIAL AND METHODS

Murine MC3T3-E1 pre-osteoblasts were treated with 10 ng/mL of TNF-α. NF-κB inhibitor, pyrrolidine dithiocarbamate, was used to achieve NF-κB signaling inhibition. EphB4 signaling was activated using ephrinB2-fc. The mRNA expressions of runt related transcription factor 2 (Runx2), bone sialoprotein (BSP) and EphB4 were determined using reverse transcription-polymerase chain reaction. The protein levels of Runx2, BSP, Col Ia1, osteopontin, EphB4, p-NF-κB p65 and NF-κB p65 were evaluated using western blot assays. Alkaline phosphatase (ALP) activity in MC3T3-E1 cells was evaluated by ALP activity kit, and mineral nodule formation was evaluated by Alizarin Red S staining.

RESULTS

TNF-α inhibited EphB4 expression, while it suppressed Runx2, BSP expression from gene and protein levels as well as ALP activity and mineral nodule formation in MC3T3-E1 cells. Activation of EphB4 signaling by ephrinB2-fc promoted osteogenic differentiation of MC3T3-E1 cells, whereas TNF-α impaired the osteogenic differentiation enhanced by ephrinB2-fc. Pyrrolidine dithiocarbamate blocked the activation of NF-κB signaling induced by TNF-α, while it prevented the downregulation of Runx2, BSP and EphB4, induced by TNF-α.

CONCLUSION

TNF-α inhibits osteogenic differentiation of pre-osteoblasts by downregulation of EphB4 signaling via activated NF-κB signaling pathway.

Plumbagin suppresses chronic periodontitis in rats via down-regulation of TNF-α, IL-1β and IL-6 expression

Chronic periodontitis (CP) is one of the most common oral diseases, which causes alveolar bone absorption and tooth loss in adults. In this study we aimed to investigate the potential of plumbagin (PL), a widely-investigated active compound extracted from the traditional Chinese herb Plumbago zeylanica L in treating CP. Human periodontal ligament stem cells (PDLSCs) were used for in vitro studies, whereas an animal model of CP was established in SD rats by ligation+Porphyromonas gingivalis (Pg) stimulation. The rats were injected with PL (2, 4, and 6 mg·kg^-1·d^-1, ip) for 4 weeks. Treatment of PDLSCs with TNF-α (10 ng/mL) markedly stimulated the expression of the proinflammatory cytokines TNF-α, IL-1β and IL-6, as well as the chemokines CCL-2 and CCL-5, which were dose-dependently suppressed by co-treatment with PL (1.25-5 μmol/L). Furthermore, PL (3.75 μmol/L) markedly suppressed TNF-α-induced activation of the MAPK, NF-κB and JAK/STAT signaling pathways in PDLSCs. In consistence with the in vitro studies, PL administration significantly decreased the expression of TNF-α, IL-1β and IL-6 in gingiva of the rat with CP, with the dosage 4 mg·kg^-1·d^-1 showing the best anti-inflammatory effect. Moreover, PL administration decelerated bone destruction in the rat with CP, evidenced by the aveolar bone loss (ABL) and H&E staining results. In conclusion, PL suppresses CP progression in rats by downregulating the expressions of TNF-α, IL-1β and IL-6 and inhibiting the MAPK, NF-κB and JAK/STAT signaling pathways.

Osteoblast Progenitors Enhance Osteogenic Differentiation of Periodontal Ligament Stem Cells

BACKGROUND

Osteoblasts and periodontal ligament stem cells (PDLSCs) play an important role in maintaining physiologic function of periodontal tissues and participating in periodontal regeneration. Elucidation of interactions between osteoblasts and PDLSCs will aid understanding of periodontal regeneration mechanisms. This study aims to determine whether preosteoblasts can promote osteoblastic/cementoblastic differentiation of PDLSCs.

METHODS

PDLSCs were cultured alone (control group), or cocultured indirectly with human gingival fibroblasts (HGFs) (HGFs group) or MC3T3-E1 cells (OB groups). Alkaline phosphatase (ALP) activity and gene/protein expressions levels of ALP, runt-related transcription factor-2, and osteopontin (OPN) were assessed. Cementum attachment protein and cementum protein 23 messenger RNA expressions were also evaluated. Bone morphogenetic protein (BMP)-2 secreted by HGFs/MC3T3-E1 cells was assessed by enzyme-linked immunosorbent assay. Extracellular matrix calcification was measured by staining to quantify calcium content.

RESULTS

ALP activity and gene/protein expression levels of osteogenic markers were significantly higher in the OB groups compared with the HGFs and control groups. Optimal enhancement of these parameters occurred at cell ratios of 2:1 to 1:1 (MC3T3-E1:PDLSCs). Mineralized nodule formation and calcium content were significantly increased in the OB groups compared with the HGF and control groups. The greatest improvement took place at the 2:1 (MC3T3-E1:PDLSCs) seeding ratio. BMP-2 from MC3T3-E1-conditioned medium was significantly and time-dependently increased compared with that from HGF-conditioned medium.

CONCLUSION

Preosteoblasts can indirectly enhance the osteoblastic/cementoblastic differentiation and mineralization of PDLSCs with an optimal preosteoblasts:PDLSCs ratio in the range of 2:1 to 1:1.

High glucose promotes the osteogenic differentiation capability of human periodontal ligament fibroblasts

Periodontal ligament fibroblasts (PDLFs) are important cells, which are involved in maintaining tooth integrity. Diabetes has been found to be associated with periodontal disease in a bidirectional manner. The aim of the present study was to investigate the stemness properties of human PDLFs (HPDLFs) in high glucose conditions. HPDLFs were analyzed for their osteogenic differentiation capacity by inducing the cells with osteogenic medium in various glucose concentrations. The gene expression was then examined using reverse transcription‑quantitative polymerase chain reaction analysis, and examinations of alkaline phosphatase activity and nodule formation were performed. The results of the gene expression analysis revealed that high glucose media induced the expression of NANOG, octamer-binding transcription factor 4, (sex determining region Y)‑box 2, cluster of differentiation 166 (CD166), PERIOSTIN and β‑CATENIN following culture of the cells for 3 days. Alkaline phosphatase activity increased following 14 days in the high glucose condition. In addition, higher numbers of calcified nodules were formed on day 28 in the group cultured with high glucose. The results showed that high glucose induced bone formation by elevating the expression of stem cell markers, particularly CD166, and this induction may be regulated through β-CATENIN.

The Regulatory Effects of Long Noncoding RNA-ANCR on Dental Tissue-Derived Stem Cells

Long noncoding RNAs (lncRNA) have been recognized as important regulators in diverse biological processes, such as transcriptional regulation, stem cell proliferation, and differentiation. Previous study has demonstrated that lncRNA-ANCR (antidifferentiation ncRNA) plays a key role in regulating the proliferation and osteogenic differentiation of periodontal ligament stem cells (PDLSCs). However, little is known about the role of ANCR in regulating other types of dental tissue-derived stem cells (DTSCs) behaviours (including proliferation and multiple-potential of differentiation). In this study, we investigated the regulatory effects of lncRNA-ANCR on the proliferation and differentiation (including osteogenic, adipogenic, and neurogenic differentiation) of DTSCs, including dental pulp stem cells (DPSCs), PDLSCs, and stem cells from the apical papilla (SCAP) by downregulation of lncRNA-ANCR. We found that downregulation of ANCR exerted little effect on proliferation of DPSCs and SCAP but promoted the osteogenic, adipogenic, and neurogenic differentiation of DTSCs. These data provide an insight into the regulatory effects of long noncoding RNA-ANCR on DTSCs and indicate that ANCR is a very important regulatory factor in stem cell differentiation.

Long noncoding RNA related to periodontitis interacts with miR-182 to upregulate osteogenic differentiation in periodontal mesenchymal stem cells of periodontitis patients

Periodontitis impairs the osteogenic differentiation of human periodontal mesenchymal stem cells (hPDLSCs), but the underlying molecular mechanisms are still poorly understood. Long noncoding RNAs (lncRNAs) have been demonstrated to have significant roles under both physiologic and pathological conditions. In this study, we performed comprehensive lncRNA profiling by lncRNA microarray analysis and identified a novel lncRNA, osteogenesis impairment-related lncRNA of PDLSCs from periodontitis patients (lncRNA-POIR), the expression of which was significantly decreased in PDLSCs from periodontitis patients (pPDLSCs) and was upregulated by osteogenic induction. To study the functions of lncRNA-POIR, we prepared cells with overexpression and knockdown of lncRNA-POIR and found that lncRNA-POIR positively regulated osteogenic differentiation of hPDLSCs and pPDLSCs both in vitro and in vivo. Using quantitative real-time PCRs (qPCRs) and luciferase reporter assays, we demonstrated that lncRNA-POIR may act as a competing endogenous RNA (ceRNA) for miR-182, leading to derepression of its target gene, FoxO1. In this process, lncRNA-POIR and miR-182 suppress each other and form a network to regulate FoxO1. FoxO1 increased bone formation of pPDLSCs by competing with TCF-4 for β-catenin and inhibiting the canonical Wnt pathway. Finally, inflammation increases miR-182 expression through the nuclear factor-κB pathway, and the miR-182 overexpression in the inflammatory microenvironment resulted in an imbalance in the lncRNA-POIR-miR-182 regulatory network. In conclusion, our results provide novel evidence that this lncRNA-miRNA (microRNA) regulatory network has a significant role in osteogenic differentiation of pPDLSCs and that it has potential as a therapeutic target in mesenchymal stem cells during inflammation.

Microenvironmental Views on Mesenchymal Stem Cell Differentiation in Aging

Aging is characterized by common environmental changes, such as hormonal, immunologic, and metabolic disorders. These pathologic factors impair the capability of mesenchymal stem cells (MSCs) to generate and maintain functionalized tissue components, contributing to age-related tissue degeneration (e.g., osteoporosis). However, in organismal aging, whether the microenvironmental signals induce common or differential MSC compromise and how they interact at the molecular level in mediating the functional decline of MSCs are not fully understood. In this review, we discuss the respective contribution of microenvironmental pathologic factors to age-related MSC dysfunction-particularly, the shifted differentiation from osteoblasts to adipocytes of bone marrow-derived MSCs. The authors summarize recent works regarding mechanisms underlying MSC-biased differentiation under altered microenvironments, which involve the activation of key signaling pathways, intracellular oxidative stress, and posttranscriptional regulations. In addition, we compare the differential influences of systemic and local microenvironments on MSC differentiation based on our findings. The authors also propose strategies to rescue differentiation disorders of MSCs in aging via modulating microenvironments, by using signaling modulators, anti-inflammatory agents, antioxidants, and metabolic regulators and by promoting mobilization of systemic MSCs to local injury sites. The authors hope that these insights contribute to MSC-based organismal aging research and treatments.

Gingival Mesenchymal Stem/Progenitor Cells: A Unique Tissue Engineering Gem

The human gingiva, characterized by its outstanding scarless wound healing properties, is a unique tissue and a pivotal component of the periodontal apparatus, investing and surrounding the teeth in their sockets in the alveolar bone. In the last years gingival mesenchymal stem/progenitor cells (G-MSCs), with promising regenerative and immunomodulatory properties, have been isolated and characterized from the gingival lamina propria. These cells, in contrast to other mesenchymal stem/progenitor cell sources, are abundant, readily accessible, and easily obtainable via minimally invasive cell isolation techniques. The present review summarizes the current scientific evidence on G-MSCs' isolation, their characterization, the investigated subpopulations, the generated induced pluripotent stem cells- (iPSC-) like G-MSCs, their regenerative properties, and current approaches for G-MSCs' delivery. The review further demonstrates their immunomodulatory properties, the transplantation preconditioning attempts via multiple biomolecules to enhance their attributes, and the experimental therapeutic applications conducted to treat multiple diseases in experimental animal models in vivo. G-MSCs show remarkable tissue reparative/regenerative potential, noteworthy immunomodulatory properties, and primary experimental therapeutic applications of G-MSCs are very promising, pointing at future biologically based therapeutic techniques, being potentially superior to conventional clinical treatment modalities.

GCN5 modulates osteogenic differentiation of periodontal ligament stem cells through DKK1 acetylation in inflammatory microenvironment

Periodontal ligament stem cells (PDLSCs) from periodontitis patients showed defective osteogenic differentiation. However, the mechanism of impaired osteogenic differentiation of PDLSCs in inflammatory microenvironments is still unclear. In this study, we found that inflammation in the microenvironment resulted in downregulation of histone acetyltransferase GCN5 expression and lack of GCN5 caused decreased osteogenic differentiation of PDLSCs. Previous study showed activated Wnt/β-cateinin pathway of PDLSCs resulted in defective osteogenic differentiation. Here we found knockdown of GCN5 decreased the expression of DKK1, an inhibitor of Wnt/β-cateinin pathway, thus activated Wnt/β-catenin pathway of PDLSCs. Mechanistically, GCN5 regulated DKK1 expression by acetylation of Histone H3 lysine 9 (H3K9) and Histone H3 lysine 14 (H3K14) at its promoter region. Interestingly, we found that in vivo injection of aspirin rescued the periodontitis of rats through inhibiting inflammation and upregulating GCN5 expression. Furthermore, aspirin treatment of PDLSCs upregulated GCN5 expression and increased osteogenic differentiation of PDLSCs. In conclusion, GCN5 plays a protective role in periodontitis through acetylation of DKK1 and applying drugs targeting GCN5, such as aspirin, could be a new approach for periodontitis treatment.

Naringin rescued the TNF-α-induced inhibition of osteogenesis of bone marrow-derived mesenchymal stem cells by depressing the activation of NF-кB signaling pathway

Naringin exhibits antiinflammatory activity and is shown to induce bone formation. Yet the impact of naringin on inflammation-affected bone marrow-derived mesenchymal stem cell (BM-MSC), a promising tool for the regenerative treatment of bone injury, remained to be investigated. We first cultured and characterized the BM-MSCs in vitro and observe the effects of treatments of TNF-α, naringin, or the combination of both on osteogenic differentiation. TNF-α administered at the concentration of 20 ng/ml results in significant reductions in MSC's cell survival, alkaline phosphatase activity and expressions of two osteogenic genes, Runx2 and Osx. Simultaneous treatment of both TNF-α and naringin is able to rescue such reductions. Further mechanistic studies indicate that TNF-α treatment activates the NF-кB signaling pathway, evidenced by elevated p-IкBα level as well as the increased nuclear fraction of NF-кB subunit, p65. Finally, treatment with both TNF-α and naringin decreases expressions of p-IкBα and nuclear p65, and thus represses NF-кB pathway activated by sole TNF-α treatment. Our findings provide a molecular basis by which naringin restores the TNF-α-induced damage in MSCs and provide novel insights into the application of naringin in the MSC-based treatments for inflammation-induced bone injury.

Autophagy regulates odontoblast differentiation by suppressing NF-κB activation in an inflammatory environment

Odontoblasts are derived from dental papilla mesenchymal cells and have an important role in defense against bacterial infection, whereas autophagy can recycle long-lived proteins and damaged organelles to sustain cellular homeostasis. Thus, this study explores the role of autophagy in odontoblast differentiation with lipopolysaccharide (LPS) stimulation in vitro and the colocalization of p-NF-κB and LC3 in caries teeth. The odontoblasts differentiation was enhanced through LPS stimulation, and this outcome was reflected in the increased number of mineralized nodules and alkaline phosphatase (ALP) activity. The expression levels of the autophagy markers LC3, Atg5, Beclin1 and TFE3 increased time dependently, as well along with the amount of autophagosomes and autophagy fluxes. This result suggests that autophagy was enhanced in odontoblasts cultured with mineralized-induced media containing LPS. To confirm the role of autophagy in differentiated odontoblasts with LPS stimulation, chloroquine (CQ) or rapamycin were used to either block or enhance autophagy. The number of mineralized nodules decreased when autophagy was inhibited, but this number increased with rapamycin treatment. Phosphorylated nuclear factor-κB (NF-κB) expression was negatively related to autophagy and could inhibit odontoblast differentiation. Furthermore, p-NF-κB and LC3 colocalization could be detected in cells stimulated with LPS. The nucleus translocation of p-NF-κB in odontoblasts was enhanced when autophagy was inhibited by Atg5 small interfering RNA. In addition, the colocalization of p-NF-κB and LC3 in odontoblasts and sub-odontoblastic layers was observed in caries teeth with reactionary dentin. Therefore, our findings provide a novel insight into the role of autophagy in regulating odontoblast differentiation by suppressing NF-κB activation in inflammatory environments.

Stem cells derived from "inflamed" and healthy periodontal ligament tissues and their sheet functionalities: a patient-matched comparison

AIM

The aim of this study was to compare the properties of stem cells derived from "inflamed" and healthy periodontal ligament (PDL) tissues from patient-matched groups.

MATERIAL AND METHODS

Patient-matched stem cells derived from root-attached "inflamed" and healthy PDL tissues from six donors, termed I-PDLSCs and H-PDLSCs, respectively, were investigated with regard to their stem cell properties, immunomodulatory effects and capacity to form robust cell sheets for therapeutic applications.

RESULTS

We found that cells derived from both sources exhibited typical mesenchymal stem cell (MSC) characteristics. However, compared with H-PDLSCs, I-PDLSCs demonstrated an increased capacity to proliferate, a greater potential to migrate and a decreased capacity to differentiate into osteoblasts in vitro. When I-PDLSCs and H-PDLSCs were co-cultured with peripheral blood mononuclear cells, the MSCs derived from "inflamed" PDL tissues exhibited impaired immunomodulation. Although I-PDLSCs led to increased collagen type I, periostin and integrin β1 content in the matrix, the cell sheets formed by I-PDLSCs were dysfunctional due to their impaired osteogenic/chondrogenic differentiation and tissue regeneration.

CONCLUSIONS

These data provide additional evidence that I-PDLSCs are functionally compromised compared with H-PDLSCs. Nonetheless, their dominant abundance in the available tissues indicates that stem cells derived from damaged teeth extracted due to periodontitis warrant further exploration.

Ordinary and Activated Bone Grafts: Applied Classification and the Main Features

Bone grafts are medical devices that are in high demand in clinical practice for substitution of bone defects and recovery of atrophic bone regions. Based on the analysis of the modern groups of bone grafts, the particularities of their composition, the mechanisms of their biological effects, and their therapeutic indications, applicable classification was proposed that separates the bone substitutes into “ordinary” and “activated.” The main differential criterion is the presence of biologically active components in the material that are standardized by qualitative and quantitative parameters: growth factors, cells, or gene constructions encoding growth factors. The pronounced osteoinductive and (or) osteogenic properties of activated osteoplastic materials allow drawing upon their efficacy in the substitution of large bone defects.

Melatonin as a candidate therapeutic drug for protecting bone cells from chlorhexidine-induced damage

BACKGROUND

Melatonin was proposed for use in periodontitis and peri-implantitis therapy due to its bone-supportive effects. This issue is of interest because standard adjuvant antiseptics, namely chlorhexidine (CHX), prove damaging for osteoblasts. Thus, the aim of this study is to investigate if melatonin is suitable as an auxiliary agent for protecting osteoblasts from CHX damage.

METHODS

MC3T3 osteoblast response was determined following administration of various CHX concentrations in the absence or presence of melatonin. Osteoblast morphology was evaluated, total reactive oxygen species (ROS) and superoxide levels were quantified, ratios of apoptotic and necrotic cells were identified by flow cytometry, metabolic activity of remaining cells was assessed, and effects were calculated with repeated measures analysis and post hoc P value adjustment.

RESULTS

CHX led to poor morphology, increased total ROS and superoxide levels, and rigorously diminished the number of vital and metabolic active osteoblasts in a concentration-dependent manner. However, simultaneous melatonin supply supported cell morphogenesis and growth, reduced ROS and superoxide generation, shifted the percentage of CHX-damaged cells from necrotic/late to early apoptotic events, and modulated metabolic activity in osteoblasts.

CONCLUSION

These data reveal that melatonin protects osteoblasts in the CHX context, thereby implicating melatonin as a promising drug in periodontitis and peri-implantitis treatment.

Artificial matrices with high-sulfated glycosaminoglycans and collagen are anti-inflammatory and pro-osteogenic for human mesenchymal stromal cells

Bone healing has been described to be most efficient if the early inflammatory phase is resolved timely. When the inflammation elevates or is permanently established, bone healing becomes impaired and, moreover, bone destruction often takes place. Systemic disorders such as diabetes and bone diseases like arthritis and osteoporosis are associated with sustained inflammation and delayed bone healing. One goal of biomaterial research is the development of materials/surface modifications which support the healing process by inhibiting the inflammatory bone erosion and suppressing pro-inflammatory mediators and by that promoting the bone repair process. In the present study, the influence of artificial extracellular matrices (aECM) on the interleukin (IL)-1β-induced pro-inflammatory response of human mesenchymal stromal cells (hMSC) was studied. hMSC cultured on aECM composed of collagen I and high-sulfated glycosaminoglycan (GAG) derivatives did not secrete IL-6, IL-8, monocyte chemoattractant protein-1, and prostaglandin E2 in response to IL-1β. The activation and nuclear translocation of nuclear factor κBp65 induced by IL-1β, tumor necrosis factor-α or lipopolysaccharide was abrogated. Furthermore, these aECM promoted the osteogenic differentiation of hMSC as determined by an increased activity of tissue non-specific alkaline phosphatase (TNAP); however, the aECM had no effect on the IL-1β-induced TNAP activity. These data suggest that aECM with high-sulfated GAG derivatives suppress the formation of pro-inflammatory mediators and simultaneously promote the osteogenic differentiation of hMSC. Therefore, these aECM might offer an interesting approach as material/surface modification supporting the bone healing process.

DKK1 rescues osteogenic differentiation of mesenchymal stem cells isolated from periodontal ligaments of patients with diabetes mellitus induced periodontitis

Multiple studies have shown that diabetes mellitus is an established risk factor for periodontitis. Recently mesenchymal stem cells derived from periodontal ligament (PDLSCs) have been utilized to reconstruct tissues destroyed by chronic inflammation. However, impact of periodontitis with diabetes mellitus on PDLSCs and mechanisms mediating effects of complex microenvironments remain poorly understood. In this study, we found multiple differentiation potential of PDLSCs from chronic periodontitis with diabetes mellitus donors (D-PDLSCs) was damaged significantly. Inhibition of NF-κB signaling could rescue osteogenic potential of PDLSCs from simple chronic periodontitis patients (P-PDLSCs), whereas did not promote D-PDLSCs osteogenesis. In addition, we found expression of DKK1 in D-PDLSCs did not respond to osteogenic signal and decreased osteogenic potential of D-PDLSCs treated with DKK1 could be reversed. To further elucidate different character between P-PDLSCs and D-PDLSCs, we treated PDLSCs with TNF-α and advanced glycation end products (AGEs), and find out AGEs which enhance effect of TNF-α in PDLSCs might mediate special personality of D-PDLSCs. The adverse effect of AGEs in PDLSCs could be reversed when PDLSCs were treated with DKK1. These results suggested DKK1 mediating WNT signaling might be a therapy target to rescue potential of PDLSCs in periodontitis with diabetes mellitus.

Periodontal ligament stem cells: current status, concerns, and future prospects

Periodontal ligament stem cells (PDLSCs), which reside in the perivascular space of the periodontium, possess characteristics of mesenchymal stem cells and are a promising tool for periodontal regeneration. Recently, great progress has been made in PDLSC transplantation. Investigators are attempting to maximize the proliferation and differentiation potential of PDLSCs by modifying culture conditions and applying growth factors. Nevertheless, problems remain. First, incomparability among different studies must be minimized by establishing standard guidelines for culture and identification of PDLSCs. Notably, attention should be paid to the biological safety of PDLSC transplantation. The present review updates the latest findings regarding PDLSCs and discusses standard criteria for culture and identification of PDLSCs. Finally, the review calls for careful consideration of PDLSC transplantation safety.

NF-κB decoy oligodeoxynucleotide enhanced osteogenesis in mesenchymal stem cells exposed to polyethylene particle

Excessive generation of wear particles after total joint replacement may lead to local inflammation and periprosthetic osteolysis. Modulation of the key transcription factor NF-κB in immune cells could potentially mitigate the osteolytic process. We previously showed that local delivery of ultrahigh-molecular-weight polyethylene (UHMWPE) particles recruited osteoprogenitor cells and reduced osteolysis. However, the biological effects of modulating the NF-κB signaling pathway on osteoprogenitor/mesenchymal stem cells (MSCs) remain unclear. Here we showed that decoy oligodeoxynucleotide (ODN) increased cell viability when primary murine MSCs were exposed to UHMWPE particles, but had no effects on cellular apoptosis. Decoy ODN increased transforming growth factor-beta 1 (TGF-β1) and osteoprotegerin (OPG) in MSCs exposed to UHMWPE particles. Mechanistic studies showed that decoy ODN upregulated OPG expression through a TGF-β1-dependent pathway. By measuring the alkaline phosphatase activity, osteocalcin levels, Runx2 and osteopontin expression, and performing a bone mineralization assay, we found that decoy ODN increased MSC osteogenic ability when the cells were exposed to UHMWPE particles. Furthermore, the cellular response to decoy ODN and UHMWPE particles with regard to cell phenotype, cell viability, and osteogenic ability was confirmed using primary human MSCs. Our results suggest that modulation of wear particle-induced inflammation by NF-κB decoy ODN had no adverse effects on MSCs and may potentially further mitigate periprosthetic osteolysis by protecting MSC viability and osteogenic ability.

The difference on the osteogenic differentiation between periodontal ligament stem cells and bone marrow mesenchymal stem cells under inflammatory microenviroments

Periodontitis is a major cause of tooth loss in adults and periodontal ligament stem cells (PDLSCs) is the most favorable candidate for the reconstruction of tissues destroyed by periodontal diseases. However, pathological alterations caused by inflammatory insults might impact the regenerative capacities of these cells. Bone-marrow-derived human mesenchymal stem cells (hBMSCs) would accelerate alveolar bone regeneration by transplantation, compared to PDLSCs. Therefore, a better understanding of the osteogenic differentiation between PDLSCs and BMSCs in inflammatory microenviroments is therefore warranted. In this study, human PDLSCs were investigated for their stem cell characteristics via analysis of cell surface marker expression, colony forming unit efficiency, osteogenic differentiation and adipogenic differentiation, and compared to BMSCs. To determine the impact of both inflammation and the NF-κβ signal pathway on osteogenic differentiation, cells were challenged with TNF-α under osteogenic induction conditions and investigated for mineralization, alkaline phosphatase (ALP) activity, cell proliferation and relative genes expression. Results showed that PDLSCs exhibit weaker mineralization and ALP activity compared to BMSCs. TNF-α inhibited genes expression of osteogenic differentiation in PDLSCs, while, it stimulates gene expressions (BSP and Runx2) in BMSCs. Enhanced NF-κβ activity in PDLSCs decreases expression of Runx2 but it does not impede the osteogenic differentiation of BMSCs. Taken together, these results may suggest that the BMSCs owned the stronger immunomodulation in local microenvironment via anti-inflammatory functions, compared to PDLSCs.

Suppression of NF-κB signaling mitigates polyethylene wear particle-induced inflammatory response

In end-stage arthritis patients, total joint replacement is a very effective surgical procedure. Nevertheless, the high revision rate after surgery remains a major concern. The wear particles generated from biomaterial-induced tissue responses may lead to chronic inflammation and local bone destruction (periprosthetic osteolysis). Several important signaling pathways are involved in wear particles induced inflammatory reactions, including the transcription factor NF-κB. We recently reported that RAW264.7 macrophage cell exposure to ultra-high molecular weight polyethylene (UHMWPE) particles significantly increased the NF-κB activity in a generated NF-κB responsive luciferase reporter cell clone. The NF-κB activity induced by UHMWPE particles in a mouse RAW264.7 macrophage cell line, bone marrow derived macrophages, and human THP1 macrophage cell line, were suppressed by double strand decoy oligodeoxynucleotide (ODN) containing an NF-κB binding element. Macrophages exposure to UHMWPE particles with or without endotoxin induced pro-inflammatory cytokine and chemokine expression including TNF-α, MCP1, MIP1α, and others. Finally, the decoy ODN significantly suppressed the induced cytokine and chemokine expression in both murine and human macrophages, consequently reducing macrophage recruitment by cellular conditioned medium exposed to wear particles. These findings suggest that local suppression of inflammatory cytokine production via inhibition of NF-κB activity with decoy ODN in total joint replacement patients could potentially be an effective strategy to alleviate wear particle-induced chronic inflammation.

Suppression of wear-particle-induced pro-inflammatory cytokine and chemokine production in macrophages via NF-κB decoy oligodeoxynucleotide: a preliminary report

Total joint replacement (TJR) is very cost-effective surgery for end-stage arthritis. One important goal is to decrease the revision rate, mainly because TJR has been extended to younger patients. Continuous production of ultra-high molecular weight polyethylene (UHMWPE) wear particles induces macrophage infiltration and chronic inflammation, which can lead to periprosthetic osteolysis. Targeting individual pro-inflammatory cytokines directly has not reversed the osteolytic process in clinical trials, owing to compensatory up-regulation of other pro-inflammatory factors. It is hypothesized that targeting the important transcription factor NF-κB could mitigate the inflammatory response to wear particles, potentially diminishing osteolysis. In the current study, NF-κB activity in mouse RAW 264.7 and human THP1 macrophage cell lines, as well as primary mouse and human macrophages, was suppressed via competitive binding with double strand decoy oligodeoxynucleotide (ODN) containing an NF-κB binding element. It was found that macrophage exposure to UHMWPE particles induced multiple pro-inflammatory cytokine and chemokine expression, including TNF-α, MCP1, MIP1α and others. Importantly, the decoy ODN significantly suppressed the induced cytokine and chemokine expression in both murine and human macrophages, and resulted in suppression of macrophage recruitment. The strategic use of decoy NF-κB ODN, delivered locally, could potentially diminish particle-induced periprosthetic osteolysis.

Lipopolysaccharide differentially affects the osteogenic differentiation of periodontal ligament stem cells and bone marrow mesenchymal stem cells through Toll-like receptor 4 mediated nuclear factor κB pathway

Introduction

Periodontitis is initiated and sustained by bacteria. However, the mechanism of bacteria induced periodontitis is still unknown. We hypothesized that bacterial components can affect the functions of stem cells in the periodontium. In this study, we comparatively investigated the influence of Lipopolysaccharide (LPS) on the osteogenesis potential of human periodontal ligament stem cells (PDLSCs) and bone marrow mesenchymal stem cells (BMMSCs).

Methods

Human PDLSCs and BMMSCs were harvested and mineralized nodule formation was assessed by alizarin red S staining. Expression level of osteogenic related gene was detected by quantitative RT-PCR (qRT-PCR). The expression of Toll-like receptor 4 (TLR4) and its downstream signaling pathway were examined by western blot. The role of TLR4 and related signaling pathway in LPS impairing the osteogenic potential of human PDLSCs and BMMSCs were also studied by alizarin red S staining and qRT-PCR. Experimental periodontitis was induced in adult Sprague–Dawley rats and the alveolar bone loss was measured by micro computed tomography analysis. The expression of alkaline phosphatase (ALP) was assessed by immunohistochemistry and the number of osteoclasts was shown by Tartrate-resistant acid phosphatase (TRAP) staining.

Results

LPS decreased the osteogenic differentiation of human PDLSCs through TLR4 regulated nuclear factor (NF)-κB pathway, but not for BMMSCs. Blocking TLR4 or NF-κB signaling partially reversed the decreased osteogenic potential of PDLSCs and prevented the alveolar bone loss caused by LPS experimental periodontitis in rats. The ALP expression in the periodontal ligament was elevated after treatment with anti-TLR4 antibody or pyrrolidinedithiocarbamate, whereas there was no statistical significance among groups for the number of osteoclasts.

Conclusions

These data suggest that LPS can activate TLR4 regulated NF-κB pathway of human PDLSCs, thus decreasing their osteogenic potential. Blockage of TLR4 or NF-κB pathway might provide a new approach for periodontitis treatment.

Novel biological strategies for treatment of wear particle-induced periprosthetic osteolysis of orthopaedic implants for joint replacement

Wear particles and by-products from joint replacements and other orthopaedic implants may result in a local chronic inflammatory and foreign body reaction. This may lead to persistent synovitis resulting in joint pain and swelling, periprosthetic osteolysis, implant loosening and pathologic fracture. Strategies to modulate the adverse effects of wear debris may improve the function and longevity of joint replacements and other orthopaedic implants, potentially delaying or avoiding complex revision surgical procedures. Three novel biological strategies to mitigate the chronic inflammatory reaction to orthopaedic wear particles are reported. These include (i) interference with systemic macrophage trafficking to the local implant site, (ii) modulation of macrophages from an M1 (pro-inflammatory) to an M2 (anti-inflammatory, pro-tissue healing) phenotype in the periprosthetic tissues, and (iii) local inhibition of the transcription factor nuclear factor kappa B (NF-κB) by delivery of an NF-κB decoy oligodeoxynucleotide, thereby interfering with the production of pro-inflammatory mediators. These three approaches have been shown to be viable strategies for mitigating the undesirable effects of wear particles in preclinical studies. Targeted local delivery of specific biologics may potentially extend the lifetime of orthopaedic implants.

Nicotine deteriorates the osteogenic differentiation of periodontal ligament stem cells through α7 nicotinic acetylcholine receptor regulating Wnt pathway

Aims

Cigarette smoking is one of the high risk factors of adult chronic periodontitis and nicotine is the well established toxic substance in cigarette. However, the mechanism of nicotine induced periodontitis is still unknown. Here we studied whether nicotine impaired the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) through activating α7 nicotinic acetylcholine receptor (α7 nAChR).

Methods

hPDLSCs with multi differentiation potential and surface makers for mesenchymal stem cells were harvested by limiting dilution technique. The level of mineralized nodule formation was assessed by alizarin red S staining. Expression level of ostegenic related genes and proteins were detected by real-time PCR and western blot analysis. The expression of α7 nAChR and its downstream signaling pathway were examined by western blot. The role of the receptor and related signaling pathway in nicotine impairing the osteogenic potential of hPDLSCs were also studied in different levels.

Results

Nicotine deteriorated the ostegenic differentiation of hPDLSCs in a dose dependent manner. Activation of α7 nAChR by nicotine treatment activated wnt/β-catenin signaling pathway, leading to osteogenic deficiency of hPDLSCs. Blockage of α7 nAChR and wnt pathway inhibitor treatment rescued nicotine induced osteogenic differentiation deficiency.

Conclusions

These data suggested that nicotine activated α7 nAChR expressed on PDLSCs and further activated wnt signaling downstream, thus deteriorating the osteogenic potential of PDLSCs. The impairment of osteogenic differentiation of PDLSCs by nicotine might lead to cigarette smoking related periodontitis.

Effect of TNFα on osteoblastogenesis from mesenchymal stem cells

BACKGROUND

Bone destruction and osteoporosis are accelerated in chronic inflammatory diseases, such as rheumatoid arthritis (RA) and periodontitis, in which many studies have shown the proinflammatory cytokines, especially TNFα, play an important role; TNFα causes osteoclast-induced bone destruction as well as the inhibition of osteoblastogenesis.

SCOPE OF REVIEW

Here we review our current understanding of the mechanism of the effect of TNFα on osteoblastogenesis from mesenchymal stem cells (MSCs). We also highlight the function of MSC in the pathogenesis of autoimmune diseases.

MAJOR CONCLUSIONS

Many studies have revealed that TNFα inhibits osteoblastogenesis through several mechanisms. On the other hand, it has been also reported that TNFα promotes osteoblastogenesis. These discrepancies may depend on the cellular types, the model animals, and the timing and duration of TNFα administration.

GENERAL SIGNIFICANCE

A full understanding of the role and function of TNFα on osteoblastogenesis from MSC may lead to targeted new therapies for chronic inflammation diseases, such as RA and periodontitis.

Urokinase receptor mediates osteogenic differentiation of mesenchymal stem cells and vascular calcification via the complement C5a receptor

Vascular calcification is a severe consequence of several pathological processes with a lack of effective therapy. Recent studies suggest that circulating and resident mesenchymal stem cells (MSC) contribute to the osteogenic program of vascular calcification. Molecular mechanisms underlying MSC osteogenic potential and differentiation remain, however, sparsely explored. We investigated a role for the complement receptor C5aR in these processes. We found that expression of C5aR was upregulated upon differentiation of human MSC to osteoblasts. C5aR inhibition by silencing and specific antagonist impaired osteogenic differentiation. We demonstrate that C5aR expression upon MSC differentiation was regulated by the multifunctional urokinase receptor (uPAR). uPAR targeting by siRNA resulted in complete abrogation of C5aR expression and consequently in the inhibition of MSC-osteoblast differentiation. We elucidated the NFκB pathway as the mechanism utilized by the uPAR-C5aR axis. MSC treatment with the NFκB inhibitor completely blocked the differentiation process. Nuclear translocation of the p65 RelA component of the NFκB complex was induced under osteogenic conditions and impaired by the inhibition of uPAR or C5aR. Dual-luciferase reporter assays demonstrated enhanced NFκB signaling upon MSC differentiation, whereas uPAR and C5aR downregulation lead to inhibition of the NFκB activity. We show involvement of the Erk1/2 kinase in this cascade. In vivo studies in a uPAR/LDLR double knockout mouse model of diet-induced atherosclerosis revealed impaired C5aR expression and calcification in aortic sinus plaques in uPAR(-/-)/LDLR(-/-) versus uPAR(+/+)/LDLR(-/-) control animals. These results suggest that uPAR-C5aR axis via the underlying NFκB transcriptional program controls osteogenic differentiation with functional impact on vascular calcification in vivo.

Canonical Wnt signaling differently modulates osteogenic differentiation of mesenchymal stem cells derived from bone marrow and from periodontal ligament under inflammatory conditions

BACKGROUND

Cellular plasticity and complex functional requirements of the periodontal ligament (PDL) assume a local stem cell (SC) niche to maintain tissue homeostasis and repair. Here, pathological alterations caused by inflammatory insults might impact the regenerative capacities of these cells. As bone homeostasis is fundamentally controlled by Wnt-mediated signals, it was the aim of this study to characterize the SC-like capacities of cells derived from PDL and to investigate their involvement in bone pathophysiology especially regarding the canonical Wnt pathway.

METHODS

PDLSCs were investigated for their SC characteristics via analysis of cell surface marker expression, colony forming unit efficiency, proliferation, osteogenic differentiation and adipogenic differentiation, and compared to bone marrow derived mesenchymal SCs (BMMSCs). To determine the impact of both inflammation and the canonical Wnt pathway on osteogenic differentiation, cells were challenged with TNF-α, maintained with or without Wnt3a or DKK-1 under osteogenic induction conditions and investigated for p-IκBα, p-NF-κB, p-Akt, β-catenin, p-GSK-3β, ALP and Runx2.

RESULTS

PDLSCs exhibit weaker adipogenic and osteogenic differentiation capacities compared to BMMSCs. TNF-α inhibited osteogenic differentiation of PDLSCs more than BMMSCs mainly through regulating canonical Wnt pathway. Blocking the canonical Wnt pathway by DKK-1 reconstituted osteogenic differentiation of PDLSCs under inflammatory conditions, whereas activation by Wnt3a increased osteogenic differentiation of BMMSCs.

CONCLUSIONS

Our results suggest a diverse regulation of the inhibitory effect of TNF-α in BMMSCs and PDLSCs via canonical Wnt pathway modulation.

GENERAL SIGNIFICANCE

These findings provide novel insights on PDLSC SC-like capacities and their involvement in bone pathophysiology under the impact of the canonical Wnt pathway.