Functions of Periostin in dental tissues and its role in periodontal tissues' regeneration

Evaluation of Random and Aligned Polycaprolactone Nanofibrous Electrospun Scaffold for Human Periodontal Ligament Engineering in Biohybrid Titanium Implants

Background: Stem cells are introduced to regenerate some living tissue to restore function and longevity. The study aims to isolate in vitro human periodontal ligament stem cells (hPDLSCs) and investigate their proliferation rate on plasma-treated aligned and random polycaprolactone (PCL) nanofibrous scaffolds made via an electrospinning technique to attempt periodontal-like tissue in dental implants. Materials and Methods: hPDLSCs were isolated from extracted human premolars and cultured on plasma-treated or untreated PCL-aligned and random scaffolds to enhance adhesion of periodontal ligament (PDL) cells as well as interaction and proliferation. Cell morphology, adhesion, and proliferation rate were evaluated using field emission scanning electron microscopy (FESEM) and the methyl tetrazolium (MTT) assay. The wettability of PCL scaffolds was tested using a goniometer. Results: The hydrophilicity of plasma-treated scaffolds was significantly increased (p ≤ 0.05) in both aligned and random nanofibers compared to the nontreated nanofibrous scaffold. Cells arranged in different directions on the random nanofiber scaffold, while for aligned scaffold nanofibers, the cells were arranged in a pattern that followed the direction of the aligned electrospun nanofibres. The rate of hPDLSC proliferation on an aligned PCL nanofiber scaffold was significantly higher than on a random PCL nanofibrous scaffold with a continuous, well-arranged monolayer of cells, as shown in FESEM. Conclusion: The aligned PCL nanofiber scaffold is superior to random PCL when used as an artificial scaffold for hPDLSC regeneration in PDL tissue engineering applications.

Targeted Reprogramming of Pathogenic Fibroblast Genes at the 3'-Untranslated Regions by DNA Nanorobots for Periodontitis

Periodontitis, with its persistent nature, causes significant distress for most sufferers. Current treatments, such as mechanical cleaning and surgery, often fail to fully address the underlying overactivation of fibroblasts that drives this degradation. Targeting the post-transcriptional regulation of fibroblasts, particularly at the 3'-untranslated regions (3'UTR) of pathogenic genes, offers a therapeutic strategy for periodontitis. Herein, we developed a DNA nanorobot for this purpose. This system uses a dynamic DNA nanoframework to incorporate therapeutic microRNAs through molecular recognition and covalent bonds, facilitated by DNA monomers modified with disulfide bonds. The assembled-DNA nanoframework is encapsulated in a cell membrane embedded with a fibroblast-targeting peptide. By analyzing the 3'UTR regions of pathogenic fibroblast genes FOSB and JUND, we identified the therapeutic microRNA as miR-1-3p and integrated it into this system. As expected, the DNA nanorobot delivered the internal components to fibroblasts by the targeting peptide and outer membrane that responsively releases miR-1-3p under intracellular glutathione. It resulted in a precise reduction of mRNA and suppression of protein function in pathogenic genes, effectively reprogramming fibroblast behavior. Our results confirm that this approach not only mitigates the inflammation but also promotes tissue regeneration in periodontal models, offering a promising therapeutic avenue for periodontitis.

Enhancing clinical safety in bioengineered-root regeneration: The use of animal component-free medium

Background

Most studies used animal serum-containing medium for bioengineered-root regeneration, but ethical and safety issues raised by animal serum are a potentially significant risk for clinical use. Thus, this study aimed to find a safer method for bioengineered-root regeneration.

Methods

The biological properties of human dental pulp stem cells (hDPSCs) cultured in animal component-free (ACF) medium or serum-containing medium (5%, 10% serum-containing medium, SCM) were compared in vitro. hDPSCs were cultured in a three-dimensional (3D) environment with human-treated dentin matrix (hTDM). The capacity for odontogenesis was compared using quantitative real-time PCR (qPCR) and Western blot. Subsequently, the hDPSCs/hTDM complexes were transplanted into nude mice subcutaneously. Histological staining was then used to verify the regeneration effect in vivo.

Results

ACF medium promoted the migration of hDPSCs, but slightly inhibited the proliferation of hDPSCs in the first three days of culture compared to SCM. However, it had no significant effect on cell aging and apoptosis. After 7 days of 3D culture in ACF medium with hTDM, qPCR showed that DMP1, DSPP, OCN, RUNX2, and β-tubulin III were highly expressed in hDPSCs. In addition, 3D cultured hDPSCs/hTDM complexes in ACF medium regenerated dentin, pulp, and periodontal ligament-like tissues similar to SCM groups in vivo.

Conclusion

ACF medium was proved to be an alternative medium for bioengineered-root regeneration. The strategy of using ACF medium to regenerate bioengineered-root can improve clinical safety for tooth tissue engineering.

Temporal and spatial expression analysis of periostin in mice periodontitis model

OBJECTIVES

This study aimed to investigate the temporal and spatial changes in the expression of periostin during periodontal inflammation in mice.

METHODS

A periodontitis model was constructed using silk thread ligation. Mice were randomly divided into five groups including control group, 4-day ligation group, 7-day ligation group, 14-day ligation group, and self-healing group (thread removal for 14 days after 14-day ligation). Micro-CT and histological staining were performed to characterize the dynamic changes in the mouse periodontal tissue in each group. RNAscope and immunohistochemical staining were used to analyze the pattern of changes in periostin at various stages of periodontitis. The cell experiment was divided into three groups: control group, lipopolysaccharide (LPS) stimulation group (treated with LPS for 12 h), and LPS stimulation removal group (treated with LPS for 3 h followed by incubation with medium for 9 h). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of periostin, transforming growth factor-β1 (TGF-β1), and matrix metalloproteinase 2 (MMP2).

RESULTS

Significant alveolar bone resorption was observed 7 days after ligation. With increasing duration of ligation, the damage to the mouse periodontal tissue was aggravated, which manifested as increased osteoclasts, widening of the periodontal membrane space, and decreased alveolar bone height. Some degree of periodontal tissue repair was observed in the self-healing group. Periostin expression decreased at 4 and 7 days compared with the control group and increased at 14 days compared with 4 and 7 days. A significant recovery was found in the self-healing group. The qRT-PCR results showed that the expression of periostin and TGF-β1 in the LPS stimulation group decreased compared with that in the control group but significantly recovered in the LPS removal group.

CONCLUSIONS

Periostin expression in the PDL of mice showed a downward and upward trend with inflammation progression. The significant recovery of periostin expression after removing inflammatory stimuli may be related to TGF-β1, which is crucial to maintain the integrity of the PDL.

4-META/MMA-TBB resin containing nano hydroxyapatite induces the healing of periodontal tissue repair in perforations at the pulp chamber floor

We aimed to evaluate the materials based on 4-methacryloxyethyl trimellitate anhydride/methyl methacrylate tri-n-butylborane (Super-bond [SB]) and nano hydroxyapatite (naHAp) for the repair of perforation at pulp chamber floor (PPF) in vitro and in vivo models. SB and naHAp were mixed in the mass ratio of 10% or 30% to produce naHAp/SB. Human periodontal ligament stem cells (HPDLSCs) were cultured on resin discs of SB or naHAp/SB to analyze the effects of naHAp/SB on cell adhesion, proliferation, and cementoblastic differentiation. A rat PPF model was treated with SB or naHAp/SB to examine the effects of naHAp/SB on the healing of defected cementum and periodontal ligament (PDL) at the site of PPF. HPDLSCs were spindle-shaped and adhered to all resin discs. Changing the resin from SB to naHAp/SB did not significantly alter cell proliferation. Both 10% and 30% naHAp/SB were more effective than SB in promoting cementoblastic differentiation of HPDLSCs. In the rat PPF model, 30% naHAp/SB was more effective than SB in promoting the formation Sharpey's fiber-like structures with expression of the PDL-related marker and cementum-like structures with expression of cementum-related markers. In conclusion, 30% naHAp/SB can be the new restorative material for PPF because it exhibited the abilities of adhering to dentin and healing of defected periodontal tissue.

Periapical lesion-derived decellularized extracellular matrix as a potential solution for regenerative endodontics

Pulp regeneration remains a crucial target in the preservation of natural dentition. Using decellularized extracellular matrix is an appropriate approach to mimic natural microenvironment and facilitate tissue regeneration. In this study, we attempted to obtain decellularized extracellular matrix from periapical lesion (PL-dECM) and evaluate its bioactive effects. The decellularization process yielded translucent and viscous PL-dECM, meeting the standard requirements for decellularization efficiency. Proteomic sequencing revealed that the PL-dECM retained essential extracellular matrix components and numerous bioactive factors. The PL-dECM conditioned medium could enhance the proliferation and migration ability of periapical lesion-derived stem cells (PLDSCs) in a dose-dependent manner. Culturing PLDSCs on PL-dECM slices improved odontogenic/angiogenic ability compared to the type I collagen group. In vivo, the PL-dECM demonstrated a sustained supportive effect on PLDSCs and promoted odontogenic/angiogenic differentiation. Both in vitro and in vivo studies illustrated that PL-dECM served as an effective scaffold for pulp tissue engineering, providing valuable insights into PLDSCs differentiation. These findings pave avenues for the clinical application of dECM's in situ transplantation for regenerative endodontics.

Characterisation and Expression of Osteogenic and Periodontal Markers of Bone Marrow Mesenchymal Stem Cells (BM-MSCs) from Diabetic Knee Joints

Type 2 diabetes mellitus (T2DM) represents a significant health problem globally and is linked to a number of complications such as cardiovascular disease, bone fragility and periodontitis. Autologous bone marrow mesenchymal stem cells (BM-MSCs) are a promising therapeutic approach for bone and periodontal regeneration; however, the effect of T2DM on the expression of osteogenic and periodontal markers in BM-MSCs is not fully established. Furthermore, the effect of the presence of comorbidities such as diabetes and osteoarthritis on BM-MSCs is also yet to be investigated. In the present study, BM-MSCs were isolated from osteoarthritic knee joints of diabetic and nondiabetic donors. Both cell groups were compared for their clonogenicity, proliferation rates, MSC enumeration and expression of surface markers. Formation of calcified deposits and expression of osteogenic and periodontal markers were assessed after 1, 2 and 3 weeks of basal and osteogenic culture. Diabetic and nondiabetic BM-MSCs showed similar clonogenic and growth potentials along with comparable numbers of MSCs. However, diabetic BM-MSCs displayed lower expression of periostin (POSTN) and cementum protein 1 (CEMP-1) at Wk3 osteogenic and Wk1 basal cultures, respectively. BM-MSCs from T2DM patients might be suitable candidates for stem cell-based therapeutics. However, further investigations into these cells' behaviours in vitro and in vivo under inflammatory environments and hyperglycaemic conditions are still required.

Autophagy mediates cementoblast mineralization under compression through periostin/β-catenin axis

Repair of orthodontic external root resorption and periodontal tissue dysfunction induced by mechanical force remains a clinical challenge. Cementoblasts are vital in cementum mineralization, a process important for restoring damaged cementum. Despite autophagy plays a role in mineralization under various environmental stimuli, the underlying mechanism of autophagy in mediating cementoblast mineralization remains unclear. Here we verified that murine cementoblasts exhibit compromised mineralization under compressive force. Autophagy was indispensable for cementoblast mineralization, and autophagic activation markedly reversed cementoblast mineralization and prevented cementum damage in mice during tooth movement. Subsequently, messenger RNA sequencing analyses identified periostin (Postn) as a mediator of autophagy and mineralization in cementoblasts. Cementoblast mineralization was significantly inhibited following the knockdown of Postn. Furthermore, Postn silencing suppressed Wnt signaling by modulating the stability of β-catenin. Together our results highlight the role of autophagy in cementoblast mineralization via Postn/β-catenin signaling under compressive force and may provide a new strategy for the remineralization of cementum and regeneration of periodontal tissue.

In vitro activity of hyaluronic acid and human serum on periodontal biofilm and periodontal ligament fibroblasts

OBJECTIVES

A beneficial effect of cross-linked hyaluronic acid (cHA) on periodontal wound healing and regeneration has recently been demonstrated. The present in vitro study was designed to obtain deeper knowledge on the effect of cHA when applied in the gingival sulcus (serum-rich environment) during non-surgical periodontal therapy.

MATERIALS AND METHODS

The influence of cHA, human serum (HS), and cHA/HS on (i) a 12-species biofilm formation, (ii) the adhesion of periodontal ligament fibroblasts (PDLF) to dentine surface, (iii) the expression and secretion of interleukin-8, and (iv) the expression of receptors of HA in PDLF and gingival fibroblasts (GF) were evaluated.

RESULTS

At 4 h of biofilm formation, cHA and HS in combination (cHA/HS) slightly decreased the colony-forming unit counts in biofilm whereas the metabolic activity of biofilm was reduced in all test groups (cHA, HS, cHA/HS) vs. control. At 24 h, the quantity of biofilm was reduced in all test groups vs. untreated control. The test substances did not affect adhesion of PDLF to dentin. HS increased the expression of IL-8 by PDLF and GF which was partially downregulated by cHA. HS and/or cHA promoted the expression of the HA receptor RHAMM in GF but not in PDLF.

CONCLUSIONS

In summary, the present data indicate that serum neither negatively affect the activity of cHA against periodontal biofilm nor had any unwanted influence on the activity of PDLF.

CLINICAL RELEVANCE

These findings lend additional support for the positive effects of cHA on cells involved in periodontal wound healing, thus pointing to its potential use in non-surgical periodontal therapy.

Dental Follicle Stem Cells Promote Periodontal Regeneration through Periostin-Mediated Macrophage Infiltration and Reprogramming in an Inflammatory Microenvironment

Dental follicle stem cells (DFSCs) have been verified to promote periodontal regeneration in an inflammatory microenvironment. When coping with inflammatory stimulation, DFSCs highly express periostin, a bioactive molecule closely related to periodontal homeostasis. It is worth exploring whether and how periostin plays a role in the promotion of periodontal regeneration by DFSCs. By tracking the fate of DFSCs, it was found that DFSCs significantly contributed to periodontal regeneration in rat periodontal defects while they had a low survival rate. They highly expressed periostin and improved the immune microenvironment in the defect area, especially via the recruitment and reprogramming of macrophages. Silencing periostin attenuated the effects of DFSCs in promoting periodontal regeneration and regulating macrophages. Recombinant human periostin (rhPeriostin) could not only directly promote macrophage reprogramming through the integrin αM/phosphorylated extracellular signal-regulated kinase (p-Erk)/Erk signaling pathway, but it also exhibited the potential to promote periodontal regeneration in rats when loaded in a collagen matrix. These results indicated that periostin is actively involved in the process by which DFSCs promote periodontal regeneration through the regulation of macrophages and is a promising molecular agent to promote periodontal regeneration. This study provides new insight into the mechanism by which DFSCs promote periodontal regeneration and suggests a new approach for periodontal regeneration therapy.

Composite Graded Melt Electrowritten Scaffolds for Regeneration of the Periodontal Ligament-to-Bone Interface

Periodontitis is a ubiquitous chronic inflammatory, bacteria-triggered oral disease affecting the adult population. If left untreated, periodontitis can lead to severe tissue destruction, eventually resulting in tooth loss. Despite previous efforts in clinically managing the disease, therapeutic strategies are still lacking. Herein, melt electrowriting (MEW) is utilized to develop a compositionally and structurally tailored graded scaffold for regeneration of the periodontal ligament-to-bone interface. The composite scaffolds, consisting of fibers of polycaprolactone (PCL) and fibers of PCL-containing magnesium phosphate (MgP) were fabricated using MEW. To maximize the bond between bone (MgP) and ligament (PCL) regions, we evaluated two different fiber architectures in the interface area. These were a crosshatch pattern at a 0/90° angle and a random pattern. MgP fibrous scaffolds were able to promote in vitro bone formation even in culture media devoid of osteogenic supplements. Mechanical properties after MgP incorporation resulted in an increase of the elastic modulus and yield stress of the scaffolds, and fiber orientation in the interfacial zone affected the interfacial toughness. Composite graded MEW scaffolds enhanced bone fill when they were implanted in an in vivo periodontal fenestration defect model in rats. The presence of an interfacial zone allows coordinated regeneration of multitissues, as indicated by higher expression of bone, ligament, and cementoblastic markers compared to empty defects. Collectively, MEW-fabricated scaffolds having compositionally and structurally tailored zones exhibit a good mimicry of the periodontal complex, with excellent regenerative capacity and great potential as a defect-specific treatment strategy.

Periodontal tissue regeneration by recombinant human collagen peptide granules applied with β-tricalcium phosphate fine particles

OBJECTIVES

Recombinant human collagen peptide (RCP) is a recombinantly created xeno-free biomaterial enriched in arginine-glycine-aspartic acid sequences with good processability whose use for regenerative medicine applications is under investigation. The biocompatibility and osteogenic ability of RCP granules combined with β-tricalcium phosphate (TCP) submicron particles (β-TCP/RCP) were recently demonstrated. In the present study, β-TCP/RCP was implanted into experimental periodontal tissue defects created in beagles to investigate its regenerative effects.

METHODS

An RCP solution was lyophilized, granulated, and thermally cross-linked into particles approximately 1 mm in diameter. β-TCP dispersion (1 wt%; 500 μL) was added to 100 mg of RCP granules to form β-TCP/RCP. A three-walled intrabony defect (5 mm × 3 mm × 4 mm) was created on the mesial side of the mandibular first molar and filled with β-TCP/RCP.

RESULTS

A micro-computed tomography image analysis performed at 8 weeks postoperative showed a significantly greater amount of new bone after β-TCP/RCP grafting (2.2-fold, P < 0.05) than after no grafting. Histological findings showed that the transplanted β-TCP/RCP induced active bone-like tissue formation including tartaric acid-resistant acid phosphatase- and OCN-positive cells as well as bioabsorbability. Ankylosis did not occur, and periostin-positive periodontal ligament-like tissue formation was observed. Histological measurements performed at 8 weeks postoperative revealed that β-TCP/RCP implantation formed 1.7-fold more bone-like tissue and 2.1-fold more periodontal ligament-like tissue than the control condition and significantly suppressed gingival recession and epithelial downgrowth (P < 0.05).

CONCLUSIONS

β-TCP/RCP implantation promoted bone-like and periodontal ligament-like tissue formation, suggesting its efficacy as a periodontal tissue regenerative material.

Wnt/β-Catenin Signaling Inhibits Osteogenic Differentiation in Human Periodontal Ligament Fibroblasts

The periodontal ligament is a collagenous tissue that is important for maintaining the homeostasis of cementum and alveolar bone. In tendon cells, Wnt/β-catenin signaling has been reported to regulate the expression level of Scleraxis (Scx) and Mohawk Homeobox (Mkx) gene and maintain the tissue homeostasis, while its role in the periodontal ligament is unclear. The aim of this study was to investigate the effects of Wnt/β-catenin signaling induced by Wnt-3a stimulation on the inhibition of osteogenic differentiation of human periodontal ligament fibroblasts (HPLFs). During osteogenic differentiation of HPLFs, they formed bone nodules independently of alkaline phosphatase (ALP) activity. After stimulation of Wnt-3a, the expression of β-catenin increased, and nuclear translocation of β-catenin was observed. These data indicate that Wnt-3a activated Wnt/β-catenin signaling. Furthermore, the stimulation of Wnt-3a inhibited the bone nodule formation and suppressed the expression of osteogenic differentiation-related genes such as Runx2, Osteopontin and Osteocalcin, and upregulated the gene expression of Type-I collagen and Periostin (Postn). Scx may be involved in the suppression of osteogenic differentiation in HPLFs. In conclusion, Wnt/β-catenin signaling may be an important signaling pathway that inhibits the osteogenic differentiation in HPLFs by the upregulation of Scx gene expression and downregulation of osteogenic differentiation-related genes.

Roles of exosomes in regenerative periodontology: a narrative review

Periodontitis is the primary cause of irreversible destruction of the periodontium surrounding teeth. Proinflammatory cytokines are secreted by pathogens in the biofilm and destroy the periodontium. Exosomes released into all biological fluids from saliva have enabled many innovations in the early diagnosis and treatment of periodontal diseases. This narrative review describes the role of exosomes in various diseases, and their involvement in periodontal diseases and periodontal regeneration primarily. Since guided tissue regeneration offers unpredictable results that vary according to the case, new developments in periodontal treatment are needed. Exosomes are suitable drug carriers for periodontal regeneration due to their isolation from every biological fluid, biocompatibility, low toxicity and high concentration of drugs reaching the target tissue. Exosomes obtained from mesenchymal stem cells can be used for periodontal regeneration in periodontal flaps, scaffolds, or periodontal defect areas through biomaterials such as drugs and hydrogels. Exosomes are significant in the early diagnosis and development of treatment of many diseases such as cardiovascular, neurodegenerative, diabetes and prognostic markers in cancer. Future studies are needed to elucidate the effects and possible mechanisms of exosomes in periodontitis and periodontal diseases and other systemic diseases, as they have many promises in diagnosis, treatment, and prognosis.

3D Polycaprolactone/Gelatin-Oriented Electrospun Scaffolds Promote Periodontal Regeneration

Periodontitis is a worldwide chronic inflammatory disease, where surgical treatment still shows an uncertain prognosis. To break through the dilemma of periodontal treatment, we fabricated a three-dimensional (3D) multilayered scaffold by stacking and fixing electrospun polycaprolactone/gelatin (PCL/Gel) fibrous membranes. The biomaterial displayed good hydrophilic and mechanical properties. Besides, we found human periodontal ligament stem cell (hPDLSC) adhesion and proliferation on it. The following scanning electron microscopy (SEM) and cytoskeleton staining results proved the guiding function of fibers to hPDLSCs. Then, we further analyzed periodontal regeneration-related proteins and mRNA expression between groups. In vivo results in a rat acute periodontal defect model confirmed that the topographic cues of materials could directly guide cellular orientation and might provide the prerequisite for further differentiation. In the aligned scaffold group, besides new bone regeneration, we also observed that angular concentrated fiber regeneration in the root surface of the defect is similar to the normal periodontal tissue. To sum up, we have constructed electrospun membrane-based 3D biological scaffolds, which provided a new treatment strategy for patients undergoing periodontal surgery.

Evaluation of IL-23p19/Ebi3 (IL-39) gingival crevicular fluid levels in periodontal health, gingivitis, and periodontitis

Objectives

IL-23p19/Ebi3 (IL-39) was described as a new IL-12 family member. The aim of this study is to evaluate the gingival crevicular fluid (GCF) IL-39 levels in periodontal diseases and health and to correlate them to GCF levels of IL-1β and periostin.

Materials and methods

Sixty-six adult patients were included in the study. The study design was comprised of three groups, each containing 22 individuals: the periodontally healthy (PH), gingivitis (G), and periodontitis (P) groups. The clinical periodontal parameters were recorded and GCF samples were collected from the participants. GCF interleukin (IL)-39, IL-1β, and periostin levels were examined using the enzyme-linked immunosorbent assay.

Results

GCF IL‑1β, periostin, and IL-39 levels were higher in the P and G groups than in the PH group (p < 0.001). Positive correlations were detected between all GCF biochemical parameters and clinical periodontal parameters (p < 0.05). In the multivariate generalized linear regression analysis, the P (β = 37.6, 95% CI = 22.9–52.4) and G (β = 28.4, 95% CI = 15.8–41) groups were associated with GCF IL-39 levels (p < 0.001).

Conclusion

IL-39 levels were elevated in the presence of periodontal disease paralleling the increase in IL‑1β and periostin levels. IL-39 may have a role in the periodontal inflammation process.

Statement of clinical relevance

IL-39, a new cytokine from the IL-12 family, can be a possible predictor marker of periodontal diseases.

Biomimetic Tubular Matrix Induces Periodontal Ligament Principal Fiber Formation and Inhibits Osteogenic Differentiation of Periodontal Ligament Stem Cells

Periodontal ligament (PDL) is assembled from highly organized collagen fiber bundles (PDL principal fibers) that are crucial in supporting teeth and buffering mechanical force. Therefore, regeneration of PDL needs to reconstruct these well-ordered fiber bundles to restore PDL functions. However, the formation of PDL principal fibers has long been a challenge due to the absence of an effective three-dimensional (3D) matrix to guide the growth of periodontal ligament stem cells (PDLSCs) and to inhibit the osteogenic differentiation of PDLSCs during the PDL principal fibers deposition. In this work, we designed and fabricated a bio-inspired tubular 3D matrix to guide the migration and growth of human PDLSCs and form well-aligned PDL principal fibers. As a biomimetic 3D template, the tubular matrix controlled PDLSCs migration inside the tubules and aligned the cells to the designated direction. Inside the tubular matrix, the PDLSCs expressed PDL markers and formed oriented fiber bundles with the same size and density as those of natural PDL principal fibers. Furthermore, the tubular matrix downregulated the osteogenic differentiation of PDLSCs. A mechanism study revealed that the Yap1/Twist1 signaling pathway was involved in the inhibition of PDLSCs osteogenesis within the tubular matrix. This work provides an effective approach to induce PDLSCs to form principal fibers and gives insight into the underlying mechanism of inhibiting the osteogenic differentiation of PDLSCs in biomimetic tubular matrices.

Mechanical Compression by Simulating Orthodontic Tooth Movement in an In Vitro Model Modulates Phosphorylation of AKT and MAPKs via TLR4 in Human Periodontal Ligament Cells

Mechanical compression simulating orthodontic tooth movement in in vitro models induces pro-inflammatory cytokine expression in periodontal ligament (PDL) cells. Our previous work shows that TLR4 is involved in this process. Here, primary PDL cells are isolated and characterized to better understand the cell signaling downstream of key molecules involved in the process of sterile inflammation via TLR4. The TLR4 monoclonal blocking antibody significantly reverses the upregulation of phospho-AKT, caused by compressive force, to levels comparable to controls by inhibition of TLR4. Phospho-ERK and phospho-p38 are also modulated in the short term via TLR4. Additionally, moderate compressive forces of 2 g/cm², a gold standard for static compressive mechanical stimulation, are not able to induce translocation of Nf-kB and phospho-ERK into the nucleus. Accordingly, we demonstrated for the first time that TLR4 is also one of the triggers for signal transduction under compressive force. The TLR4, one of the pattern recognition receptors, is involved through its specific molecular structures on damaged cells during mechanical stress. Our findings provide the basis for further research on TLR4 in the modulation of sterile inflammation during orthodontic therapy and periodontal remodeling.

Osteoimmunology in Periodontitis: Local Proteins and Compounds to Alleviate Periodontitis

Periodontitis is one of the most common oral diseases resulting in gingival inflammation and tooth loss. Growing evidence indicates that it results from dysbiosis of the oral microbiome, which interferes with the host immune system, leading to bone destruction. Immune cells activate periodontal ligament cells to express the receptor activator of nuclear factor kappa-B (NF-κB) ligand (RANKL) and promote osteoclast activity. Osteocytes have active roles in periodontitis progression in the bone matrix. Local proteins are involved in bone regeneration through functional immunological plasticity. Here, we discuss the current knowledge of cellular and molecular mechanisms in periodontitis, the roles of local proteins, and promising synthetic compounds generating a periodontal regeneration effect. It is anticipated that this may lead to a better perception of periodontitis pathophysiology.

Periostin regulates LPS-induced apoptosis via Nrf2/HO-1 pathway in periodontal ligament fibroblasts

OBJECTIVE

Periostin is important for the maintenance of periodontal tissue, but its role in periodontitis is controversial. This research investigated the effect of periostin in periodontitis and the underlying mechanism.

DESIGN

Mouse periodontitis models in vivo and inflammation model in vitro which were induced by Porphyromonas gingivalis lipopolysaccharide were established to evaluate periostin expression. Human periodontal ligament fibroblasts (PDLFs) were treated with lipopolysaccharide and N-acetylcysteine, fluorescence staining, flow cytometry, western blot, and qRT-PCR were used to detect reactive oxygen species (ROS), periostin expression, and apoptosis-related makers. The periostin gene was successfully transfected into PDLFs to verify the effect of periostin on apoptosis. Then, the Nrf2 inhibitor was added to clarify the mechanism.

RESULTS

Periostin expression decreased in the periodontal ligaments of mouse periodontitis models and lipopolysaccharide-induced PDLFs. Lipopolysaccharide promoted the activation of ROS and apoptosis in PDLFs, whereas N-acetylcysteine reversed this condition. Overexpression of periostin suppressed apoptosis of PDLFs and reversed the inhibitory effect of lipopolysaccharide on nuclear Nrf2 expression. Moreover, the Nrf2 inhibitor attenuated the protective effect of periostin on lipopolysaccharide-induced apoptosis.

CONCLUSIONS

Lipopolysaccharide induced apoptosis in PDLFs by inhibiting periostin expression and thus Nrf2/HO-1 pathway, indicating that periostin could be a potential therapeutic target for periodontitis.

Effects of different methods of demineralized dentin matrix preservation on the proliferation and differentiation of human periodontal ligament stem cells

Background/purpose

Demineralized dentin matrix (DDM) is used as a tissue regeneration scaffold. Effective preservation of DDM benefits clinical applications. Cryopreservation and freeze-drying may be effective methods to retain DDM mechanical properties and biological activity.

Materials and methods

Human periodontal ligament stem cells (hPDLSCs) isolated using enzymatic dissociation were identified by multidirectional differentiation and flow cytometry. DDM was prepared with EDTA and divided into four groups: fresh DDM (fDDM), room temperature-preserved DDM (rtDDM), cryopreserved DDM (cDDM) and freeze-dried DDM (fdDDM). The DDM surface morphology was observed, and microhardness was detected. Transforming growth factor-β1 (TGF-β1), fibroblast growth factor (FGF) and collagen-Ⅰ (COL-Ⅰ) concentrations in DDM liquid extracts were detected by enzyme-linked immunosorbent assay (ELISA). The hPDLSCs were cultured with DDM liquid extracts. The effect of DDM on cells proliferation was examined by CCK-8 assay. The effect of DDM on hPDLSC secreted phosphoprotein-1 (SPP1), periostin (POSTN) and COL-Ⅰ gene expression was examined by real-time qPCR.

Results

cDDM dentinal tubules were larger than those of the other groups. The three storage conditions had no significant effect on DDM microhardness and COL-Ⅰ concentration. However, TGF-β1 and FGF concentrations decreased after storage, with the greatest change in rtDDM, followed by fdDDM and cDDM. The liquid extracts of fDDM, cDDM and fdDDM slightly inhibited hPDLSCs proliferation, but those of rtDDM had no significant effect. The hPDLSCs cultured with fDDM, cDDM and fdDDM liquid extracts showed increased SPP1, POSTN and COL-Ⅰ gene expression.

Conclusion

Cryopreservation and freeze-drying better maintain the mechanical properties and biological activity of DDM.

The profiling and analysis of gene expression in human periodontal ligament tissue and fibroblasts

Objectives

The periodontal ligament (PDL) is an important component of periodontium to support dental structure in the alveolar socket. Regeneration of PDL tissue is an effective treatment option for periodontal disease and the profiling of genes involved in this process will be informative. Therefore, our study aims to accurately delineate the profiling of gene expression for PDL tissue regeneration.

Materials and Methods

We isolated PDL tissues and PDL fibroblasts (PDLFs) from premolar teeth, which were extracted from healthy periodontal status patients undergoing orthodontic treatment. Messenger RNA (mRNA) expression in PDL tissue and PDLFs were analyzed using Cap analysis gene expression, which is a second‐generation sequencing technique to create profiling. We also determined the protein expression using Western blot.

Results

Collagens (type I, III, and VI), noncollagenous proteins (periostin and osteonectin), and proteoglycans (asporin, lumican, decorin, and osteomodulin) were highly expressed in PDL tissue. Integrin, β1 was also expressed in PDL tissue. On comparison of gene expression between PDL tissue and PDLFs, four PDL marker genes, osteopontin, asporin, periostin, and osteonectin, were decreased in PDLFs. The genes for gene regulation were also highly expressed.

Conclusions

Our study demonstrated the overall profiling of mRNA expression in PDL tissue and analyzed the important genes which may be useful for providing specific information for the reconstruction of PDL. We also identified the difference in gene expression between PDL tissue and PDLFs which might provide insights towards PDL regeneration.

Bio-hybrid dental implants prepared using stem cells with β-TCP-coated titanium and zirconia

Purpose

This study investigated periodontal ligament (PDL) restoration in osseointegrated implants using stem cells.

Methods

Commercial pure titanium and zirconium oxide (zirconia) were coated with beta-tricalcium phosphate (β-TCP) using a long-pulse Nd:YAG laser (1,064 nm). Isolated bone marrow mesenchymal cells (BMMSCs) from rabbit tibia and femur, isolated PDL stem cells (PDLSCs) from the lower right incisor, and co-cultured BMMSCs and PDLSCs were tested for periostin markers using an immunofluorescent assay. Implants with 3D-engineered tissue were implanted into the lower right central incisors after extraction from rabbits. Forty implants (Ti or zirconia) were subdivided according to the duration of implantation (healing period: 45 or 90 days). Each subgroup (20 implants) was subdivided into 4 groups (without cells, PDLSC sheets, BMMSC sheets, and co-culture cell sheets). All groups underwent histological testing involving haematoxylin and eosin staining and immunohistochemistry, stereoscopic analysis to measure the PDL width, and field emission scanning electron microscopy (FESEM). The natural lower central incisors were used as controls.

Results

The BMMSCs co-cultured with PDLSCs generated a well-formed PDL tissue that exhibited positive periostin expression. Histological analysis showed that the implantation of coated (Ti and zirconia) dental implants without a cell sheet resulted in a well-osseointegrated implant at both healing intervals, which was confirmed with FESEM analysis and negative periostin expression. The mesenchymal tissue structured from PDLSCs only or co-cultured (BMMSCs and PDLSCs) could form a natural periodontal tissue with no significant difference between Ti and zirconia implants, consequently forming a biohybrid dental implant. Green fluorescence for periostin was clearly detected around the biohybrid implants after 45 and 90 days. FESEM showed the invasion of PDL-like fibres perpendicular to the cementum of the bio-hybrid implants.

Conclusions

β-TCP-coated (Ti and zirconia) implants generated periodontal tissue and formed biohybrid implants when mesenchymal-tissue-layered cell sheets were isolated from PDLSCs alone or co-cultured BMMSCs and PDLSCs.

In-bone protein digestion followed by LC-MS/MS peptide analysis as a new way towards the routine proteomic characterization of human maxillary and mandibular bone tissue in oral surgery

Proteomic characterization of alveolar bones in oral surgery represents an analytical challenge due to their insoluble character. The implementation of a straightforward technique could lead to the routine use of proteomics in this field. This work thus developed a simple technique for the characterization of bone tissue for human maxillary and mandibular bones. It is based on the direct in-bone tryptic digestion of proteins in both healthy and pathological human maxillary and mandibular bone samples. The released peptides were then identified by the LC-MS/MS. Using this approach, a total of 1120 proteins were identified in the maxillary bone and 1151 proteins in the mandibular bone. The subsequent partial least squares-discrimination analysis (PLS-DA) of protein data made it possible to reach 100% discrimination between the samples of healthy alveolar bones and those of the bone tissue surrounding the inflammatory focus. These results indicate that the in-bone protein digestion followed by the LC-MS/MS and subsequent statistical analysis can provide a deeper insight into the field of oral surgery at the molecular level. Furthermore, it could also have a diagnostic potential in the differentiation between the proteomic patterns of healthy and pathological alveolar bone tissue. Data are available via ProteomeXchange with the identifier PXD026775.

Effects of collagen membranes and bone substitute differ in periodontal ligament cell microtissues and monolayers

BACKGROUND

Barrier membranes and bone substitute are major tools of guided tissue regeneration (GTR) after periodontal disease. Integrity of the periodontal ligament plays a key role in periodontal health, but its functionality fails to be fully re-established by GTR after disease or trauma. Microtissue models suggest an in vivo-like model to develop novel GTR approaches due to its three-dimensionality. This study aims to assess the effects of collagen membranes and bone substitute on cell viability, adhesion and gene expression of regenerative and inflammatory biomarkers by periodontal ligament cell (PDLC) microtissues.

METHODS

Human PDLC microtissues and monolayers were cultured on collagen membranes or bone substitute. After 24 hours incubation, metabolic activity, focal adhesion, mRNA and protein production of collagen-type-I (COL1A1), periostin (POSTN), vascular endothelial growth factor (VEGF), angiogenin (ANG), interleukin (IL)6 and IL8 were measured by resazurin-based toxicity assay, focal adhesion staining, quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

RESULTS

PDLC microtissues and monolayers were viable on collagen membranes and bone substitute, but microtissues were less metabolically active. Dominant staining of actin filaments was found in PDLC microtissues on collagen membranes. COL1A1, POSTN, VEGF, ANG and IL6 were modulated in PDLC microtissues on bone substitute, while there were no significant changes on collagen membranes. PDLC monolayers showed a different character of gene expression changes.

CONCLUSIONS

PDLC microtissues and monolayers react diversely to collagen membranes and bone substitute. Further descriptive and mechanistic tests will be required to clarify the potential of PDLC microtissues as in vivo-like model for GTR.

Therapeutic potential of periodontal ligament stem cells

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

Functions of Matricellular Proteins in Dental Tissues and Their Emerging Roles in Orofacial Tissue Development, Maintenance, and Disease

Matricellular proteins (MCPs) are defined as extracellular matrix (ECM) associated proteins that are important regulators and integrators of microenvironmental signals, contributing to the dynamic nature of ECM signalling. There is a growing understanding of the role of matricellular proteins in cellular processes governing tissue development as well as in disease pathogenesis. In this review, the expression and functions of different MP family members (periostin, CCNs, TSPs, SIBLINGs and others) are presented, specifically in relation to craniofacial development and the maintenance of orofacial tissues, including bone, gingiva, oral mucosa, palate and the dental pulp. As will be discussed, each MP family member has been shown to have non-redundant roles in development, tissue homeostasis, wound healing, pathology and tumorigenesis of orofacial and dental tissues.

Preservation of the viability and gene expression of human periodontal ligament cells by Thai propolis extract

BACKGROUND/AIM

Success of tooth replantation depends on the quality and quantity of periodontal ligament (PDL) cells. The aims of this study were to evaluate Thai propolis extract as a storage medium for maintaining PDL cell viability and preserving gene expressions in PDL tissues.

MATERIALS AND METHODS

PDL cells from human premolars were tested for cytotoxicity of the extract by PrestoBlue assay to determine a non-toxic concentration. Subsequently, 96 freshly extracted premolars were allocated into different treatment groups. Control groups were freshly extracted premolars or they had been stored dry for 12 hours. Experimental avulsed teeth were created by leaving them air-dried for 30 minutes immediately after extraction, then they were immersed in Thai propolis extract, HBSS or milk for 3, 6 and 12 hours. After tooth storage, the remaining PDL cells were determined for their cell viability. RNA isolated from PDL tissues of three premolars treated similarly was analysed for periostin and S100A4 expressions using RT-qPCR.

RESULTS

Thai propolis extract at 0.625 mg mL^-1 promoted the greatest PDL cell viability. Tooth storage in 0.625 mg mL^-1 Thai propolis extract, HBSS or milk showed no difference in maintaining cell viability. Periostin mRNA level was preserved by Thai propolis extract. Expression of S100A4 mRNA in PDL tissues stored in all tested media was dampened.

CONCLUSIONS

PDL cells from mock avulsed teeth stored in 0.625 mg mL^-1 Thai propolis extract for 3, 6 and 12 hours remained viable and the expression of periostin was preserved. This study suggests this extract as an alternative for a tooth storage medium for up to 12 hours. However, transporting an avulsed tooth in a storage medium for extended extra-oral time might affect the PDL cell phenotypes.

The effect of non-surgical periodontal treatment on gingival crevicular fluid periostin levels in patients with gingivitis and periodontitis

OBJECTIVE

The objective of the study was to evaluate the effect of non-surgical periodontal treatment on gingival crevicular fluid (GCF) periostin levels in patients with gingivitis (G) and periodontitis (P).

SUBJECTS AND METHODS

A total of 90 subjects, 30 patients with P, 30 with G, and 30 periodontally healthy (H) subjects were included. Patients with periodontal disease received non-surgical periodontal treatment. GCF periostin levels were assessed at baseline, at the 6th week, and the 3rd month after treatment.

RESULTS

It was found that GCF periostin level was the lowest in the H group (89.31[47.12] pg/30 sec), followed by the G group (132.82[145.14] pg/30 sec), and the highest in the P group (207.75[189.45] pg/30 sec). These differences were statistically significant between H and the other groups (p < .001). After treatment, GCF periostin levels significantly decreased at the 6th week and the 3rd month in the G group, at the 3rd month in the P group compared to baseline values (p < .05).

CONCLUSION

The results of this study suggest that GCF periostin plays a role as a reliable biological marker in the pathogenesis of periodontal disease and non-surgical periodontal treatment is effective in decreasing GCF periostin levels.

Maresin-1 and Resolvin E1 Promote Regenerative Properties of Periodontal Ligament Stem Cells Under Inflammatory Conditions

Maresin-1 (MaR1) and Resolvin E1 (RvE1) are specialized pro-resolving lipid mediators (SPMs) that regulate inflammatory processes. We have previously demonstrated the hard and soft tissue regenerative capacity of RvE1 in an in vivo model of the periodontal disease characterized by inflammatory tissue destruction. Regeneration of periodontal tissues requires a well-orchestrated process mediated by periodontal ligament stem cells. However, limited data are available on how SPMs can regulate the regenerative properties of human periodontal ligament stem cells (hPDLSCs) under inflammatory conditions. Thus, we measured the impact of MaR1 and RvE1 in an in vitro model of hPDLSC under stimulation with IL-1β and TNF-α by evaluating pluripotency, migration, viability/cell death, periodontal ligament markers (α-smooth muscle actin, tenomodulin, and periostin), cementogenic-osteogenic differentiation, and phosphoproteomic perturbations. The data showed that the pro-inflammatory milieu suppresses pluripotency, viability, and migration of hPDLSCs; MaR1 and RvE1 both restored regenerative capacity by increasing hPDLSC viability, accelerating wound healing/migration, and up-regulating periodontal ligament markers and cementogenic-osteogenic differentiation. Protein phosphorylation perturbations were associated with the SPM-induced regenerative capacity of hPDLSCs. Together, these results demonstrate that MaR1 and RvE1 restore or improve the regenerative properties of highly specialized stem cells when inflammation is present and offer opportunities for direct pharmacologic treatment of lost tissue integrity.

Differential regulation of epithelial growth by gingival and periodontal fibroblasts in vitro

OBJECTIVES

To investigate the underlying molecular mechanisms by which gingival and periodontal ligament (PDL) fibroblasts regulate epithelial phenotype.

BACKGROUND

Fibroblast populations regulate the epithelial phenotype through epithelial-mesenchymal interactions (EMI). Previous studies have proposed that maintenance of the junctional epithelium (JE) is dependent on the differential effects from gingival and PDL tissues. However, these cell populations are undefined and the signalling mechanisms which may regulate JE are unknown.

METHODS

Immunohistochemical analyses were performed on formalin-fixed paraffin-embedded sections of dentogingival tissues to identify phenotypic differences in fibroblast populations. The effect of distinct fibroblasts on epithelial phenotype was studied via 3D organotypic cultures, consisting of an H400 epithelium supported by human gingival fibroblasts (HGF) or human periodontal ligament fibroblasts (HPDLF), embedded in collagen gel. To investigate the involvement of Wnt signalling in EMI, the Wnt antagonist rhDKK1 was added to HGF constructs. The gene expression of Wnt antagonists and agonists was tested via RNA extraction and qPCR. Specific gene silencing using RNA interference was performed on HPDLF/HGF constructs.

RESULTS

Gingival fibroblasts were characterized by Sca1 expression, and PDL fibroblasts, characterized by Periostin and Asporin expression. Through the construction of 3D organotypic cultures, we showed that HGF supported epithelial multilayering, whilst HPDLF failed to support epithelial cell growth. Furthermore, HGF constructs treated with rhDKK1 resulted in a profound reduction in epithelial thickness. We identified SFRP4 to be highly specifically expressed in HPDLF, at both the mRNA and protein levels. A knockdown of SFRP4 in HPDLF constructs led to an increase in epithelial growth.

CONCLUSION

The study demonstrates the presence of phenotypically distinct fibroblast populations within dentogingival tissues and that these specific populations have different influences on the epithelium. Our data suggest that a downregulation of Wnt signalling within PDL may be important in maintaining the integrity and anatomical position of the JE.

Soft tissue healing around platform-switching and platform-matching single implants: A randomized clinical trial

BACKGROUND

Implants with platform-switching (PS) design have been demonstrated to reduce marginal bone loss. However, the influence on peri-implant soft tissue healing is unclear. This study was designed to investigate its effect on peri-implant soft tissue healing after implant uncovery.

METHODS

Non-smokers needing two implants in different quadrants were recruited in this study. For each individual, one PS and one platform-matching (PM) implants were placed using two-stage protocol. Following 2 to 8 months of healing, all implants were uncovered and connected to the corresponding healing abutments. Clinical measurements and peri-implant crevicular fluid (PICF) were taken at 1-, 2-, 4-, and 6-week after 2nd stage surgery. The cytokine concentrations in PICF were analyzed. Peri-implant mucosa (1 × 2 × 2 mm) was harvested around the healing abutment for the analysis of gene expression at uncovery and 6-week post-uncovery.

RESULTS

Eighteen participants (nine males; 51.7 ± 14.9 years) were recruited. Compared to PM, PS showed significantly lower probing depth (PD) at 1- and 2-week as well as modified sulcus bleeding index (mSBI) at 1-, 4-, and 6-week (P < 0.05). Over time, a decrease in osteoprotegerin and interleukin-1β concentrations in PICF along with an increase in receptor activator of unclear factor kappa-B ligand, periostin, and peroxidasin gene expressions in peri-implant mucosa were noted within both groups (P < 0.05) without significant intergroup differences.

CONCLUSION

Within the limits, implants with PS design rendered significant benefits over PM design in PD and mSBI reduction during a 6-week healing. However, molecular changes within PICF and peri-implant mucosa as a response to PM and PS appear negligible.

Mapping and Identification of Native Proteins of Developing Teeth in Mouse Mandibles

Mass spectrometry imaging is a powerful tool of increasing utility due to its ability to spatially resolve molecular biomarkers directly from sectioned tissues. One hindrance to its universality is that no single protocol is sufficient for every tissue type, fixation, and pretreatment. Mineralized tissues are uniquely challenging as extensive decalcification protocols are necessary to achieve thin sections. In this study, we optimized a method to image tryptic peptides by matrix-assisted laser desorption ionization mass spectrometry of decalcified, formalin-fixed paraffin-embedded mouse hemimandibles. Using a combination of on-tissue MS/MS and hydrogel extraction LC-MS/MS, peptides from the enamel, dentin, periodontal ligament, alveolar bone, pulp, and other regions are identified and mapped. This breakthrough method provides a comprehensive approach to biomarker discovery in dental and craniofacial tissues which is highly relevant given that diseases originating from this region of the body are the most prevalent across all populations.

Gelatin Nanoparticle-Injectable Platelet-Rich Fibrin Double Network Hydrogels with Local Adaptability and Bioactivity for Enhanced Osteogenesis

Bone healing is a dynamic process regulated by biochemical signals such as chemokines and growth factors, and biophysical signals such as topographical and mechanical features of extracellular matrix or mechanical stimuli. Hereby, a mechanically tough and bioactive hydrogel based on autologous injectable platelet-rich fibrin (iPRF) modified with gelatin nanoparticles (GNPs) is developed. This composite hydrogel demonstrates a double network (DN) mechanism, wherein covalent network of fibrin serves to maintain material integrity, and self-assembled colloidal network of GNPs dissipates force upon loading. A rabbit sinus augmentation model is used to investigate the bioactivity and osteogenesis capacity of the DN hydrogels. The DN hydrogels adapt to the local environmental complexity of bone defects, i.e., accommodate the irregular shape of the defects and withstand the pressure formed in the maxillary sinus during animal's respiration process. The DN hydrogel is also demonstrated to absorb and prolong the release of the bioactive growth factors stemming from iPRF, which could have contributed to the early angiogenesis and osteogenesis observed inside the sinus. This adaptable and bioactive DN hydrogel can achieve enhanced bone regeneration in treating complex bone defects by maintaining long-term bone mass and withstanding the functional mechanical stimuli.

Extracellular matrix derived from human urine-derived stem cells enhances the expansion, adhesion, spreading, and differentiation of human periodontal ligament stem cells

Background

Human periodontal ligament stem cells (hPDLSCs) are one of the most promising types of seed cells in periodontal tissue regeneration. Suitable biomaterials are additional essential components that must cooperate with seed cells for in vivo expansion or in vitro implantation. Extracellular matrix (ECM) derived from mesenchymal stem cells (MSCs) was recently reported to be a promising substrate with which to culture MSCs that could be applied in biomaterial scaffolds or bioink. Human urine-derived stem cells (hUSCs) have several advantages; their collection is non-invasive and easy, and hUSCs are low in cost, potentially making them a suitable and efficient source of ECM. The purpose of this study was to characterize the biological properties of ECM derived from hUSCs (UECM) and evaluate the effects of UECM on hPDLSCs.

Methods

hPDLSCs grown on ECM derived from hPDLSCs (PECM) and fibronectin-coated tissue culture plastic (TCP) served as control groups. Both hUSCs and hPDLSCs were seeded on TCP and stimulated to produce ECM. After 8 days of stimulation, the samples were decellularized, leaving only ECM. Then, hPDLSCs were seeded onto UECM-, PECM-, and fibronectin-coated TCP and untreated TCP.

Results

UECM consists of dense bundles of fibers which contain abundant fibronectin. Both UECM and PECM promoted hPDLSC proliferation, attachment, spreading, and differentiation. Between UECM and PECM, UECM enhanced proliferation, osteogenesis, and angiogenesis to a greater extent. Though fibronectin appeared to be the abundant component of UECM, its performance was inferior to that of UECM.

Conclusions

Our study provides an original perspective on different cell-specific ECMs and suggests UECM as a suitable biomaterial in which to culture hPDLSCs as UECM enhances their biological functions.

Regeneration characteristics of different dental derived stem cell sheets

BACKGROUND

Although cell sheets have gained much interest as a non-scaffold strategy for tissue regeneration, the regenerative features of different cell sheets remain unclear.

OBJECTIVE

In this study, we aimed to compare the regeneration characteristics of cell sheets derived from dental pulp stem cells (DPSCs), periodontal ligament stem cells (PDLSCs) and stem cells of the apical papilla (SCAPs).

METHODS

Dental pulp stem cells, PDLSCs and SCAPs from the same individual were acquired and induced to form sheets using 20 μg/mL vitamin C. Immunofluorescence staining was used to detect the expression of collagen I, fibronectin, integrin β1 and vimentin. Real-time PCR was used to determine NANOG, OCT4, SOX2 and TERT gene expression. The cell sheets with hydroxyapatite/tricalcium phosphate were transplanted into nude mice subcutaneously to evaluate tissue regeneration characteristics.

RESULTS

No obvious differences were found in the histological structure and extracellular matrix protein expression between DPSC, PDLSC and SCAP sheets. Dental pulp stem cell sheet showed higher expression of OCT4 and TERT than PDLSC and SCAP sheets. All three cell sheets displayed the ability of mineral tissue formation and highly expressed periostin. The tissue derived from DPSC sheet showed higher CD31 expression and porous fibres compared with that from the others. The tissue fibres formed from PDLSC sheet were directionally arranged, while the tissue derived from SCAP sheet showed highest mineral tissue formation.

CONCLUSION

Although in vitro DPSC, PDLSC and SCAP cell sheets have similar characteristics, their regenerative characteristics in vivo are different, with each showing potential application for regeneration of different tissues.

Mesenchymal stem cell exosomes enhance periodontal ligament cell functions and promote periodontal regeneration

Mesenchymal stem cells (MSCs) are potential therapeutics for the treatment of periodontal defects. It is increasingly accepted that MSCs mediate tissue repair through secretion of trophic factors, particularly exosomes. Here, we investigated the therapeutic effects of human MSC exosome-loaded collagen sponge for regeneration of surgically created periodontal intrabony defects in an immunocompetent rat model. We observed that relative to control rats, exosome-treated rats repaired the defects more efficiently with regeneration of periodontal tissues including newly-formed bone and periodontal ligament (PDL). We also observed that concomitant with this, there was increased cellular infiltration and proliferation. We therefore postulated that MSC exosomes enhanced regeneration through increased cellular mobilisation and proliferation. Using PDL cell cultures, we demonstrated that MSC exosomes could increase PDL cell migration and proliferation through CD73-mediated adenosine receptor activation of pro-survival AKT and ERK signalling. Inhibition of AKT or ERK phosphorylation suppressed PDL cell migration and proliferation. Our findings demonstrated for the first time that MSC exosomes enhance periodontal regeneration possibly by increasing PDL migration and proliferation. This study suggests that MSC exosome is a viable ready-to-use and cell-free MSC therapeutic for the treatment of periodontal defects. STATEMENT OF SIGNIFICANCE: Mesenchymal stem cell (MSC) therapies have demonstrated regenerative potential for the treatment of periodontal defects. However, translation of cellular therapies is hampered by challenges in maintaining optimal cell vitality and viability from manufacturing and storage to final delivery to patients. Although the use of MSCs for tissue repair was first predicated on their differentiation potential, the therapeutic efficacy of MSCs has increasingly been attributed to its paracrine secretion, particularly exosomes or small extracellular vesicles. In this study, MSC exosome-loaded collagen sponge enhanced periodontal regeneration in an immunocompetent rat periodontal defect model without any obvious adverse effects. These findings provide the basis for future development of MSC exosomes as a cell-free strategy for periodontal regeneration.

Periostin and Human Teeth

Periostin is a secreted matricellular protein that primarily interacts with type I collagen and fibronectin extracellular matrix proteins, and is widely distributed in tissues rich in collagen-rich connective tissues, including the periodontal ligament. Its expression in these tissues is especially regulated by mechanical load. While the expression and regulation of periostin in the teeth of murine models and cell lines is well known, its presence in human teeth is poorly documented. Here we update and summarize the available data on the distribution of periostin in the human periodontal ligament, gingiva and dental pulp.

Gelatin-assisted conglutination of aligned polycaprolactone nanofilms into a multilayered fibre-guiding scaffold for periodontal ligament regeneration

The repair or regeneration of well-aligned periodontal ligaments (PDL) remains a challenging clinical task in reconstructive surgeries and regenerative medicine. Topographical cell guidance has been utilized as a tissue-engineering bionic technique and facilitates the geometric design of composite materials. In this investigation, we manufactured multilayered scaffolds by cementing aligned polycaprolactone (PCL) electrospun films together using gelatin; the fibre-guiding scaffold mimicked the natural structure of periodontal ligaments and was aimed at promoting the growth of functionally oriented ligamentous fibres in vivo. Experiments in vitro demonstrated that this scaffold could provide good attachment and tissue-mimicking microenvironments for "seeding cells", that is, human periodontal ligament mesenchyme cells (PDLSCs). Histological and immunofluorescence results indicated that a three-dimensional aligned construct could significantly enhance the angulation of new-born PDL-like tissue and facilitate collagen formation and maturation at periodontal fenestration defects compared to an amorphous PCL embedded scaffold. Multilayered fibre-guiding scaffold made of PCL and gelatin was demonstrated to be applicable for oriented neogenesis of periodontium, and it may represent an important potential application for dental stem cell delivery for periodontal regenerative medicine.

Evaluating the oxysterol combination of 22(S)-hydroxycholesterol and 20(S)-hydroxycholesterol in periodontal regeneration using periodontal ligament stem cells and alveolar bone healing models

BACKGROUND

Oxysterols, oxygenated by-products of cholesterol biosynthesis, play roles in various physiological and pathological systems. However, the effects of oxysterols on periodontal regeneration are unknown. This study investigated the effects of the specific oxysterol combination of 22(S)-hydroxycholesterol and 20(S)-hydroxycholesterol (SS) on the regeneration of periodontal tissues using in-vitro periodontal ligament stem cells (PDLSCs) and in-vivo models of alveolar bone defect.

METHODS

To evaluate the effects of the combined oxysterols on PDLSC biology, we studied the SS-induced osteogenic differentiation of PDLSCs by assessing alkaline phosphatase activity, intracellular calcium levels [Ca²⁺]_i, matrix mineralization, and osteogenic marker mRNA expression and protein levels. To verify the effect of oxysterols on alveolar bone regeneration, we employed tooth extraction bone defect models.

RESULTS

Oxysterols increased the osteogenic activity of PDLSCs compared with the control group. The expression of liver X receptor (LXR) α and β, the nuclear receptors for oxysterols, and their target gene, ATP-binding cassette transporter A1 (ABCA1), increased significantly during osteogenesis. Oxysterols also increased protein levels of the hedgehog (Hh) receptor Smo and the transcription factor Gli1. We further confirmed the reciprocal reaction between the LXRs and Hh signaling. Transfection of both LXRα and LXRβ siRNAs decreased Smo and Gli1 protein levels. In contrast, the inhibition of Hh signaling attenuated the LXRα and LXRβ protein levels. Subsequently, SS-induced osteogenic activity of PDLSCs was suppressed by the inhibition of LXRs or Hh signaling. The application of SS also enhanced bone formation in the defect sites of in-vivo models, showing equivalent efficacy to recombinant human bone morphogenetic protein-2.

CONCLUSIONS

These findings suggest that a specific combination of oxysterols promoted periodontal regeneration by regulating PDLSC activity and alveolar bone regeneration.