Osteogenic Differentiation Of Periodontal Ligament Cells Research Articles

Nanosilicate-functionalized nanofibrous membrane facilitated periodontal regeneration potential by harnessing periodontal ligament cell-mediated osteogenesis and immunomodulation

Although various new biomaterials have enriched the methods for periodontal regeneration, their efficacy is still controversial, and the regeneration of damaged support tissue in the periodontium remains challenging. Laponite (LAP) nanosilicate is a layered two-dimensional nanoscale, ultrathin nanomaterial with a unique structure and brilliant biocompatibility and bioactivity. This study aimed to investigate the effects of nanosilicate-incorporated PCL (PCL/LAP) nanofibrous membranes on periodontal ligament cells (PDLCs) in vitro and periodontal regeneration in vivo. A PCL/LAP nanofibrous membrane was fabricated by an electrospinning method. The characterization of PCL/LAP nanofibrous membrane were determined by scanning electron microscopy (SEM), energy dispersive spectrum of X-ray (EDS), inductively coupled plasma mass spectrometry (ICP-MS) and tensile test. The proliferation and osteogenic differentiation of PDLCs on the PCL/LAP nanofibrous membrane were evaluated. A PDLCs and macrophage coculture system was used to explore the immunomodulatory effects of the PCL/LAP nanofibrous membrane. PCL/LAP nanofibrous membrane was implanted into rat calvarial and periodontal defects, and the regenerative potential was evaluated by microcomputed topography (micro-CT) and histological analysis. The PCL/LAP nanofibrous membrane showed good biocompatibility and bioactivity. It enhanced the proliferation and osteogenic differentiation of PDLCs. The PCL/LAP nanofibrous membrane also stimulated anti-inflammatory and pro-remodeling N2 neutrophil formation, regulated inflammatory responses and induced M2 macrophage polarization by orchestrating the immunomodulatory effects of PDLCs. The PCL/LAP nanofibrous membrane promoted rat calvarial defect repair and periodontal regeneration in vivo. LAP nanosilicate-incorporated PCL membrane is capable of mediating osteogenesis and immunomodulation of PDLCs in vitro and accelerating periodontal regeneration in vivo. It could be a promising biomaterial for periodontal regeneration therapy.

Intracellular glucose starvation inhibits osteogenic differentiation in human periodontal ligament cells

Periodontal ligament cells (PDLCs), as mesenchymal cells in the oral cavity, are closely linked to periodontal tissue regeneration. However, the effect of local glucose deficiency on periodontal tissue regeneration, such as immediately post-surgery, remains unknown. In the present study, we investigated the effect of a low-glucose environment on the proliferation and osteogenic differentiation of PDLCs. We used media with five glucose concentrations (100, 75, 50, 25, and 0mg/dL) and focused on the effects of a low-glucose environment on the proliferation, osteogenic differentiation, and autophagy of PDLCs. Additionally, we focused on changes in lactate production in a low-glucose environment and investigated the involvement of lactate with AZD3965, a monocarboxylate transporter-1 (MCT-1) inhibitor. The low-glucose environment inhibited PDLCs proliferation, migration, and osteogenic differentiation, and induced the expression of the autophagy-related factors LC3 and p62. Lactate and ATP production were decreased under low-glucose conditions. The addition of AZD3965 (MCT-1 inhibitor) in normal glucose conditions caused a similar trend as in low-glucose conditions on PDLCs. Our results suggest lactate production through glucose metabolism in the osteogenic differentiation of PDLCs. A low-glucose environment decreased lactate production, inhibiting cell proliferation, migration, and osteogenic differentiation and inducing autophagy in PDLCs.

Baicalein inhibits inflammatory response and promotes osteogenic activity in periodontal ligament cells challenged with lipopolysaccharides

BackgroundPeriodontitis is a chronic infection initiated by oral bacterial and their virulence factors, yet the severity of periodontitis is largely determined by the dysregulated host immuno-inflammatory response. Baicalein is a flavonoid extracted from Scutellaria baicalensis with promising anti-inflammatory properties. This study aims to clarify the anti-inflammatory and osteogenic effects of baicalein in periodontal ligament cells (PDLCs) treated with lipopolysaccharides (LPS).MethodsHuman PDLCs were incubated with baicalein (0–100 μM) for 2 h prior to LPS challenge for 24 h. MTT analysis was adopted to assess the cytoxicity of baicalein. The mRNA and protein expression of inflammatory and osteogenic markers were measured by real-time polymerase chain reaction (PCR), western blot and enzyme-linked immunosorbent assay (ELISA) as appropriate. Alkaline phosphatase (ALP) and Alizarin red S (ARS) staining were performed to evaluate the osteogenic differentiation of PDLCs. The expression of Wnt/β-catenin and mitogen-activated protein kinase (MAPK) signaling related proteins was assessed by western blot.ResultsMTT results showed that baicalein up to 100 μM had no cytotoxicity on PDLCs. Baicalein significantly attenuated the inflammatory factors induced by LPS, including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), matrix metalloprotein-1 (MMP-1), MMP-2 and monocyte chemoattractant protein 1 (MCP-1) at both mRNA and protein level. Moreover, MAPK signaling (ERK, JNK and p38) was significantly inhibited by baicalein, which may account for the mitigated inflammatory response. Next, we found that baicalein effectively restored the osteogenic differentiation of LPS-treated PDLCs, as shown by the increased ALP and ARS staining. Accordingly, the protein and gene expression of osteogenic markers, namely runt-related transcription factor 2 (RUNX2), collagen-I, and osterix were markedly upregulated. Importantly, baicalein could function as the Wnt/β-catenin signaling activator, which may lead to the increased osteoblastic differentiation of PDLCs.ConclusionsWith the limitation of the study, we provide in vitro evidence that baicalein ameliorates inflammatory response and restores osteogenesis in PDLCs challenged with LPS, indicating its potential use as the host response modulator for the management of periodontitis.

Study of endoplasmic reticulum stress response in osteogenic differentiation of human periodontal ligament cells

The aim of this study was to establish whether endoplasmic reticulum (ER) stress is involved in osteogenic differentiation of periodontal ligament cells (PDLCs) and to better understand the mechanism of PDLCs osteogenic differentiation. PDLCs were isolated from extracted teeth and cultured in presence or absence of osteogenic medium, which can induce osteogenic differentiation of PDLCs. Alkaline phosphatase and alizarin red S staining were performed to characterize the osteogenic differentiation of PDLCs. The mRNA and protein levels of ER stress markers were examined by RT-PCR and Western blot analysis. The data were analyzed with SPSS 17.0 software package. Cell treated with osteogenic medium showed increased expression of alkaline phosphatase, increased matrix, and mineralized nodule formation compared with untreated controls. Treatment with osteogenic induction resulted in up-regulation of genes, such as splicing x-box binding protein-1 (sXBP1), activating transcription factor 4 (ATF4) and glucose-regulated protein 78 (GRP78). The expressions of ER stress protein markers, phosphorylated RNA-activated protein kinase-like ER-resident kinase (p-PERK), phosphorylated eukaryotic initiation factor-2α (p-eIF2α), increased in osteogenic induction cells compared with controls. The results indicate that ER stress response is involved in the process of osteogenic differentiation of PDLCs.

MicroRNA‐195‐5p Regulates Osteogenic Differentiation of Periodontal Ligament Cells Under Mechanical Loading

Osteogenic differentiation and bone formation are tightly regulated by several factors, including microRNAs (miRNAs). However, miRNA expression patterns and function during mechanical loading-induced osteogenic differentiation of human periodontal ligament cells (PDLCs) remain unclear. Here, we investigated the differential expression of miRNA-195-5p in the periodontal tissues of mice under orthodontic mechanical loading and in primary human PDLCs exposed to a simulated tension strain. The miR-195-5p was observed to be down-regulated and negatively correlated with osteogenic differentiation. Overexpression of miR-195-5p significantly inhibited PDLC differentiation under cyclic tension strain (CTS), whereas the functional inhibition of miR-195-5p yielded an opposite effect. Further experiments confirmed that WNT family member 3A (WNT3A), fibroblast growth factor 2 (FGF2), and bone morphogenetic protein receptor-1A (BMPR1A), proteins important for osteogenic activity and stability, were direct targets of miR-195-5p. Mechanical loading increased the WNT3A, FGF2, and BMPR1A protein levels, while miR-195-5p inhibited WNT3A, FGF2, and BMPR1A protein expression. WNT, FGF, and BMP signaling were involved in osteogenic differentiation of PDLCs under CTS. Further study confirmed that reintroduction of WNT3A and BMPR1A can rescue the inhibition of miR-195-5p on osteogenic differentiation of PDLCs. Our findings are the first to demonstrate that miR-195-5p is a mechanosensitive gene that plays an important role in mechanical loading-induced osteogenic differentiation and bone formation.

Rho-kinase regulates extracellular matrix-mediated osteogenic differentiation of periodontal ligament cells.

The periodontal ligament (PDL) cells contain heterogeneous mesenchymal cell populations, which have the ability to differentiate into cells that produce adjacent mineralized tissues and abundant extracellular matrix (ECM). ECM is essential not only for the homeostasis of the periodontal tissue, but also for controlling the differentiation of the PDL cells. The process of differentiation involves mechanotransduction, which links the ECM to the cytoskeleton. The present study investigated the roles of Rho-associated coiled-coil containing protein kinase (ROCK) signaling, a crucial regulator of the cytoskeleton, during ECM-mediated osteogenic differentiation of PDL cells in vitro. The PDL cells were isolated from human periodontal ligaments of extracted teeth and cultured in osteogenic medium with or without Y-27632, a pharmacological inhibitor of ROCK. ECM-coated plates were used for ECM-mediated differentiation. The osteogenic phenotype was evaluated at different time points by real-time RT-PCR for the gene encoding alkaline phosphatase (ALP) and an ALP activity assay. The effects of ROCK on cytoskeletal changes and ECM synthesis were examined by immunofluorescence analysis. Y-27632 significantly inhibited ALP at the mRNA and protein activity levels in the late stage of differentiation; concomitantly, the actin filament content and the extracellular levels of collagen-I and fibronectin were markedly decreased by Y-27632. Exogenous collagen-I and fibronectin temporally increased ALP activity, with fibronectin showing a more pronounced effect. Importantly, ECM-mediated differentiation was almost completely inhibited by Y-27632. These findings indicated that ECM-mediated differentiation is dependent on ROCK signaling, and ROCK signaling contributes to the establishment of the ECM microenvironment for PDL cell differentiation.

PERK-eIF2α-ATF4 pathway mediated by endoplasmic reticulum stress response is involved in osteodifferentiation of human periodontal ligament cells under cyclic mechanical force

To prevent excess accumulation of unfolded proteins in endoplasmic reticulum (ER), eukaryotic cells have signaling pathways from the ER to the cytosol or nucleus. These processes are known as the endoplasmic reticulum stress (ERS) response. Protein kinase R like endoplasmic reticulum kinase (PERK) is a major transducer of the ERS response and it directly phosphorylate α-subunit of eukaryotic initiation factor 2 (eIF2α), resulting in translational attenuation. Phosphorylated eIF2α specifically promoted the translation of the activating transcription factor 4 (ATF4). ATF4 is a known important transcription factor which plays a pivotal role in osteoblast differentiation and bone formation. Furthermore, ATF4 is a downstream target of PERK. Studies have shown that PERK-eIF2α-ATF4 signal pathway mediated by ERS was involved in osteoblastic differentiation of osteoblasts. We have known that orthodontic tooth movement is a process of periodontal ligament cells (PDLCs) osteodifferentiation and alveolar bone remodeling under mechanical force. However, the involvement of PERK-eIF2α-ATF4 signal pathway mediated by ERS in osteogenic differentiation of PDLCs under mechanical force has not been unclear. In our study, we applied the cyclic mechanical force at 10% elongation with 0.5Hz to mimic occlusal force, and explored whether PERK-eIF2α-ATF4 signaling pathway mediated by ERS involved in osteogenic differentiation of PDLCs under mechanical force. Firstly, cyclic mechanical force will induce ERS and intensify several osteoblast marker genes (ATF4, OCN, and BSP). Next, we found that PERK overexpression increased eIF2α phosphorylation and expression of ATF4, furthermore induced BSP, OCN expression, thus it will promote osteodifferentiation of hPDLCs; mechanical force could promote this effect. However, PERK−/− cells showed the opposite changes, which will inhibit osteodifferentiation of hPDLCs. Taken together, our study proved that PERK-eIF2α-ATF4 signaling pathway mediated by ERS involved in osteoblast differentiation of PDLCs under cyclic mechanical force.

Endogenous hydrogen sulfide is involved in osteogenic differentiation in human periodontal ligament cells

ObjectiveEndogenous hydrogen sulfide (H2S) has recently emerged as an important intracellular gaseous signaling molecule within cellular systems. Endogenous H2S is synthesized from l-cysteine via cystathionine β-synthase and cystathionine γ-lyase and it regulates multiple signaling pathways in mammalian cells. Indeed, aberrant H2S levels have been linked to defects in bone formation in experimental mice. The aim of this study was to examine the potential production mechanism and function of endogenous H2S within primary human periodontal ligament cells (PDLCs). DesignPrimary human PDLCs were obtained from donor molars with volunteer permission. Immunofluorescent labeling determined expression of the H2S synthetase enzymes. These enzymes were inhibited with D,L-propargylglycine or hydroxylamine to examine the effects of H2S signaling upon the osteogenic differentiation of PDLCs. Gene and protein expression levels of osteogenic markers in conjunction with ALP staining and activity and alizarin red S staining of calcium deposition were used to assay the progression of osteogenesis under different treatment conditions. Cultures were exposed to Wnt3a treatment to assess downstream signaling mechanisms. ResultsIn this study, we show that H2S is produced by human PDLCs via the cystathionine β-synthase/cystathionine γ-lyase pathway to promote their osteogenic differentiation. These levels must be carefully maintained as excessive or deficient H2S levels temper the observed osteogenic effect by inhibiting Wnt/β-catenin signaling. ConclusionsThese results demonstrate that optimal concentrations of endogenous H2S must be maintained within PDLCs to promote osteogenic differentiation by activating the Wnt/β-catenin signaling cascade.

Identification of endoglin-dependent BMP-2-induced genes in the murine periodontal ligament cell line PDL-L2.

BackgroundThe periodontal ligament (PDL), connective tissue located between the cementum of teeth and alveolar bone of the mandibula, plays an important role in the maintenance and regeneration of periodontal tissues. We reported previously that endoglin was involved in the BMP-2-induced osteogenic differentiation of mouse PDL cells, which is associated with Smad-2 phosphorylation but not Smad-1/5/8 phosphorylation. In this study, to elucidate the detailed mechanism underlying the BMP-2 signalling pathway unique to PDL cells, we performed a microarray analysis to identify BMP-2-inducible genes in PDL-L2 cells, a mouse PDL-derived cell line, with or without endoglin knockdown.FindingsSixty-four genes were upregulated more than twofold by BMP-2 in PDL-L2 cells. Of these genes, 11 were endoglin-dependent, including Id4, which encodes ID4, a helix-loop-helix transcription factor closely associated with TGF-β signaling and osteoblast differentiation. The endoglin-dependent induction of ID4 by BMP-2 was also verified at a protein level.ConclusionOur findings indicate that ID4 could be a signal mediator involved in the BMP-2-induced endoglin-dependent osteogenic differentiation of PDL cells.

Porous nagelschmidtite bioceramic scaffolds with improved in vitro and in vivo cementogenesis for periodontal tissue engineering

Bioactive scaffolds play an important role in periodontal tissue engineering. Nagelschmidtite (NAGEL:Ca7P2Si2O16) is a newly synthesized bioceramic which can stimulate the proliferation and osteogenic/cementogenic differentiation of periodontal ligament cells (PDLCs) for potential periodontal regeneration. The aim of this study is to prepare porous NAGEL scaffolds and to systematically investigate their in vitro and in vivo osteogenesis/cementogenesis. The NAGEL scaffold with highly porous structure and large pores was successfully prepared by a spongy-templated method. The interaction of the NAGEL scaffold with PDLCs was studied by investigating cell attachment, proliferation and osteogenic differentiation of PDLCs. NAGEL scaffolds were implanted into the periodontal defects of beagle dogs to evaluate their in vivo osteogenesis/cementogenesis. The results showed that NAGEL scaffolds supported the attachment and proliferation of PDLCs, and significantly enhanced osteogenesis/cementogenesis-related gene expression of PDLCs, compared to β-TCP scaffolds. The in vivo study showed that the rate of new bone formation in NAGEL scaffolds was higher than that in conventional β-TCP scaffolds, which was evidenced by the significantly improved BSP and OPN expression at both 4 and 8 weeks. The results suggested that NAGEL scaffolds could be used for periodontal tissue engineering with significantly improved in vitro and in vivo osteogenesis/cementogenesis.

MiR-21 and miR-101 regulate PLAP-1 expression in periodontal ligament cells

Periodontal ligament-associated protein-1 (PLAP-1/asporin) is a special marker in periodontal ligament tissue. It is an important regulator of osteogenic differentiation of periodontal ligament cells (PDLCs). This marker is also a prerequisite for periodontal ligament development and mineralization in maintaining homeostasis of the periodontium. However, the molecular mechanisms of the regulation of PLAP-1 expression at the post-transcriptional level remain unknown. By contrast, microRNAs (miRNAs) provide an additional level of regulation beyond that of transcription factors via regulation of the post-transcriptional control of gene expression. This study was designed to analyze miRNA differential expression patterns of PDLCs at various osteoblastic differentiation stages and to determine the contribution of miRNAs in the regulation of PLAP-1 expression during osteoblast differentiation. Bioinformatic analysis was performed to predict miRNAs that potentially regulate the gene expression of PLAP-1. Dual luciferase reporter assay and qRT-PCR were performed to confirm the effects of these miRNAs on PLAP-1 gene expression. Our results indicated that mir-101 and mir-21 target PLAP-1 to regulate its expression during osteogenic differentiation of PDLCs.

Periodontal regeneration using novel glycidyl methacrylated dextran (Dex-GMA)/gelatin scaffolds containing microspheres loaded with bone morphogenetic proteins

The objective of this study was to evaluate the biological activity enhancement of a novel glycidyl methacrylated dextran (Dex-GMA)/gelatin hybrid hydrogel containing microspheres loaded with bone morphogenetic proteins (BMP) as periodontal cell/tissue scaffold. Larger number of human periodontal ligament cells (PDLCs) attached was observed in scaffolds containing microspheres loaded with BMP when compared to those without microspheres. When osteogenic differentiation of PDLCs in such scaffolds was evaluated, the alkaline phosphatase (ALP) activity, osteocalcin content, and calcium deposition became maximum for the scaffold containing microspheres loaded with BMP, as compared with those without microspheres but adsorbed with the same amount of BMP aqueous solution, although both values were significantly higher than those in BMP-free scaffold. In addition, the osteoinduction activity was also studied following the implantation of these scaffolds into the periodontal defects of dogs in terms of histological examinations, significantly more new bone formation and periodontal ligaments regeneration were observed throughout scaffold containing microspheres. We conclude that the attachment, proliferation, and osteogenic differentiation of PDLCs can be enhanced by Dex-GMA/gelatin hydrogel scaffold containing microspheres loaded with BMP, and such scaffold is promising to enhance periodontal tissue regeneration in periodontal therapy.