Leucine-rich alpha-2-glycoprotein 1 affects bone destruction via IL-6 in mouse periodontitis model

OBJECTIVE

To investigate the production of leucine-rich α-2-glycoprotein-1 (LRG1) in periodontitis patients and its effectiveness as a new diagnostic marker for periodontitis.

SUBJECTS AND METHODS

In vitro experiments were conducted to analyze LRG1 mRNA expression in human gingival epithelial cells and fibroblasts via quantitative real-time PCR. In vivo experiments were conducted to analyze LRG1 localization in periodontitis patients. The correlation between the serum LRG1 levels and alveolar bone resorption in the mouse periodontitis model was also investigated.

RESULTS

A positive correlation existed between the periodontal inflamed surface area and serum LRG1 levels (Spearman's rank correlation coefficient: 0.60). LRG1 mRNA expression in human gingival epithelial cells and fibroblasts was upregulated by Porphyromonas gingivalis stimulation or tumor necrosis factor-α stimulation. Interleukin-6 in human gingival epithelial cells and fibroblasts induced the production of LRG1 and transforming growth factor-β. LRG1 levels in the periodontal tissue and serum in the periodontitis model were higher than those in control mice. LRG1 local administration resulted in alveolar bone resorption, whereas the administration of interleukin-6R antibody inhibited bone resorption.

CONCLUSIONS

LRG1 levels in serum and periodontal tissue are upregulated in periodontitis and are implicated in periodontal tissue destruction through interleukin-6 production.

Predictive factors of periodontal regeneration outcomes using rhFGF-2: A case-control study

OBJECTIVE

This study aimed to investigate the factors influencing the clinical outcomes of regenerative therapy using recombinant human fibroblast growth factor-2 (rhFGF-2).

BACKGROUND

rhFGF-2 promotes periodontal regeneration, and identifying the factors influencing this regeneration is important for optimizing the effectiveness of rhFGF-2.

METHODS AND MATERIALS

This study used a hospital information-integrated database to identify patients who underwent periodontal regenerative therapy with rhFGF-2. Factors included age, smoking status, diabetes mellitus (DM), periodontal inflamed surface area (PISA) at the initial visit, whether the most posterior tooth was involved or not, and preoperative radiological bone defect angle. Periodontal regenerative therapy outcomes were defined as good if radiographic bone fill ≥35% or periodontal pocket closure at 9-15 months after surgery. Bone fill rate (%) and periodontal pocket depth (mm) were also used as outcome measures. Factors were evaluated by simple regression analysis, and then the association between factors and the outcomes was determined by multivariate analysis.

RESULTS

PISA and age at the first visit did not significantly influence the success or failure of bone fill rate byrhFGF-2. However, DM, radiographic bone defect angle, and the most posterior tooth significantly influenced the regenerative effect (success/failure in bone fill) of rhFGF-2. The most posterior tooth was significantly associated with bone fill rate by rhFGF-2. Examination of the association between pocket closure and factors shows that the most posterior tooth significantly influenced. The most posterior tooth and preoperative PPD were significantly associated with pocket reduction depth. For the most posterior tooth, a significantly higher bone regeneration rate (p < .05) was observed with a combination of autologous bone graft and rhFGF-2 than with rhFGF-2 alone, and the effect was significant in multivariate analysis.

CONCLUSIONS

The radiographic bone defect angle, the involvement of most posterior teeth, and the presence of DM influenced the effectiveness of rhFGF-2 in periodontal regeneration. However, PISA values and age at the initial visit had no significant effect.

Periodontal tissue regeneration with cementogenesis after application of brain-derived neurotrophic factor in 3-wall inflamed intra-bony defect

OBJECTIVE

The purpose of this study is to investigate regenerative process by immunohistochemical analysis and evaluate periodontal tissue regeneration following a topical application of BDNF to inflamed 3-wall intra-bony defects.

BACKGROUND

Brain-derived neurotrophic factor (BDNF) plays a role in the survival and differentiation of central and peripheral neurons. BDNF can regulate the functions of non-neural cells, osteoblasts, periodontal ligament cells, endothelial cells, as well as neural cells. Our previous study showed that a topical application of BDNF enhances periodontal tissue regeneration in experimental periodontal defects of dog and that BDNF stimulates the expression of bone (cementum)-related proteins and proliferation of human periodontal ligament cells.

METHODS

Six weeks after extraction of mandibular first and third premolars, 3-wall intra-bony defects were created in mandibular second and fourth premolars of beagle dogs. Impression material was placed in all of the artificial defects to induce inflammation. Two weeks after the first operation, BDNF (25 and 50 μg/mL) immersed into atelocollagen sponge was applied to the defects. As a control, only atelocollagen sponge immersed in saline was applied. Two and four weeks after the BDNF application, morphometric analysis was performed. Localizations of osteopontin (OPN) and proliferating cell nuclear antigen (PCNA)-positive cells were evaluated by immunohistochemical analysis.

RESULTS

Two weeks after application of BDNF, periodontal tissue was partially regenerated. Immunohistochemical analyses revealed that cells on the denuded root surface were positive with OPN and PCNA. PCNA-positive cells were also detected in the soft connective tissue of regenerating periodontal tissue. Four weeks after application of BDNF, the periodontal defects were regenerated with cementum, periodontal ligament, and alveolar bone. Along the root surface, abundant OPN-positive cells were observed. Morphometric analyses revealed that percentage of new cementum length and percentage of new bone area of experimental groups were higher than control group and dose-dependently increased.

CONCLUSION

These findings suggest that BDNF could induce cementum regeneration in early regenerative phase by stimulating proliferation of periodontal ligament cells and differentiation into periodontal tissue cells, resulting in enhancement of periodontal tissue regeneration in inflamed 3-wall intra-bony defects.

Periostin regulates integrin expression in gingival epithelial cells

OBJECTIVE

Human gingival epithelial cells (HGECs) function as a mechanical barrier against invasion by pathogenic organisms through epithelial cell-cell junction complexes, which are complex components of integrin. Integrins play an important role in the protective functions of HGECs. Human periodontal ligament (HPL) cells regulate periodontal homeostasis. However, periodontitis results in the loss of HPL cells. Therefore, as replenishment, HPL cells or mesenchymal stem cells (MSCs) can be transplanted. Herein, HPL cells and MSCs were used to elucidate the regulatory mechanisms of HGECs, assuming periodontal tissue homeostasis.

METHODS

Human gingival fibroblasts (HGFs), HGECs, HPL cells, and MSCs were cultured, and the conditioned medium was collected. With or without silencing periostin mRNA, HGECs were cultured under normal conditions or in a conditioned medium. Integrin and periostin mRNA expression was determined using real-time polymerase chain reaction. Integrin protein expression was analyzed using flow cytometry, and periostin protein expression was determined via western blotting.

RESULTS

The conditioned medium affected integrin expression in HGECs. Higher expression of periostin was observed in MSCs and HPL cells than in HGFs. The conditioned medium that contained periostin protein regulated integrin expression in HGECs. After silencing periostin in MSCs and HPL cells, periostin protein was not detected in the conditioned medium, and integrin expression in HGECs remained unaffected.

CONCLUSIONS

Integrins in HGECs are regulated by periostin secreted from HPL cells and MSCs. This result suggests that periostin maintains gingival cell adhesion and regulates bacterial invasion/infection. Therefore, the functional regulation of periostin-secreting cells is important in preventing periodontitis.

Effect of cognitive load and working memory capacity on the efficiency of discovering better alternatives: A survival analysis

Why do humans attempt to discover better alternatives to solve a problem even when they know the way to solve it? This question is related to the flexibility of thinking and is the subject of studies on the Einstellung effect. This study focuses on cognitive load for familiar trained procedure as a factor that influences the discovery of alternatives in Einstellung situations, where the problem can be solved using a trained procedure. Many studies on creative problem solving and strategy selection demonstrate that cognitive load for facilitates the discovery of alternatives. However, findings are inconsistent regarding Einstellung situations. We argue that the reason for such inconsistent results were the use of manipulations such as the double task, which both load on the trained and alternative procedure and the lack of perspective on efficiency in analysis. Therefore, we examine the relationship between cognitive load manipulated by the complexity of the trained procedure and time-based performance measured by the number of trials prior to finding alternatives. The results illustrate that higher cognitive load increased the efficiency of discovery of alternatives and that this effect was significant for participants with high working memory capacity. This study provides empirical evidence that high cognitive load for trained procedure facilitates the discovery of alternatives and suggests the importance of considering temporal properties, such as efficiency, when examining the effects of working memory on problem solving, which requires cognitive flexibility.

Mechanosignaling YAP/TAZ-TEAD Axis Regulates the Immunomodulatory Properties of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have gained significant attention in cell therapies due to their multipotency and immunomodulatory capacities. The transcriptional co-activators YAP/TAZ, central to the mechanotransduction system in MSCs, dominantly direct MSCs lineage commitment. However, their role in immunomodulation remains elusive. Accordingly, this present study aimed to investigate the role of mechanotransducer YAP/TAZ and their binding target transcriptional factor, TEAD, in the immunomodulatory capacities of human bone marrow-derived MSCs. Reducing YAP/TAZ activity by altering the matrix stiffness, disrupting the F-actin integrity with chemical inhibitors, or using siRNAs increased the expression of immunomodulatory genes, such as TSG-6 and IDO, upon TNF-α stimulation. Similarly, transfection of TEAD siRNA also increased the immunomodulatory capacities in MSCs. RNA-seq analysis and inhibition assays demonstrated that the immunomodulatory capacities caused by YAP/TAZ-TEAD axis disruption were due to the NF-κB signaling pathway activation. Then, we also evaluated the in vivo anti-inflammatory efficacy of MSCs in a dextran sulfate sodium (DSS)-induced mice colitis model. The administration of human MSCs transfected with TEAD siRNA, which exhibited enhanced immunomodulatory properties in vitro, significantly ameliorated inflammatory bowel disease symptoms, such as body weight loss and acute colon inflammation, in the DSS-induced mice colitis model. Our findings underscore the mechanosignaling YAP/TAZ-TEAD axis as a regulator of MSCs immunomodulation. Targeting these signaling pathways could herald promising MSCs-based therapies for immune disorders.

Relationship between CD4+ T-cell counts at baseline and initial periodontal treatment efficacy in patients undergoing treatment for HIV infection: A retrospective observational study

AIM

To retrospectively investigate the relationship between the CD4+ T-cell counts at baseline and the efficacy of the initial periodontal treatment of patients undergoing treatment for human immunodeficiency virus (HIV) infection using the periodontal inflamed surface area (PISA).

MATERIALS AND METHODS

Thirty-three patients with chronic periodontitis who had undergone periodontal examination at baseline and after the initial periodontal treatment were enrolled. PISA was calculated from the periodontal probing depth and bleeding on probing, and the ratio of PISA after treatment to that at baseline (PISA response ratio) was calculated. Groups with a response ratio of <1 and ≥1 were defined as the improvement and the non-improvement groups, respectively.

RESULTS

PISA after the initial periodontal treatment significantly decreased compared with that at baseline (p < .05). A weak negative correlation was found between the PISA response ratio and CD4+ T-cell counts at baseline (p < .05). The CD4+ T-cell counts at baseline were significantly higher in the improvement group than in the non-improvement group (p < .05). Multivariate analysis revealed that the CD4+ T-cell counts at baseline was an independent factor that affects the PISA (p < .05).

CONCLUSIONS

The higher the CD4+ T-cell counts at baseline in patients undergoing treatment for HIV infection, the more effective the initial periodontal treatment.

A Cartilaginous Construct with Bone Collar Exerts Bone-Regenerative Property Via Rapid Endochondral Ossification

Three-dimensional clumps of mesenchymal stem cells (MSCs)/extracellular matrix (ECM) complexes (C-MSCs) can be implanted into tissue defects with no artificial scaffolds. In addition, the cellular properties and characteristics of the ECM in C-MSCs can be regulated in vitro. Most bone formation in the developmental and healing process is due to endochondral ossification, which occurs after bone collar formation surrounding cartilage derived from MSCs. Thus, to develop a rapid and reliable bone-regenerative cell therapy, the present study aimed to generate cartilaginous tissue covered with a mineralized bone collar-like structure from human C-MSCs by combining chondrogenic and osteogenic induction. Human bone marrow-derived MSCs were cultured in xeno-free/serum-free (XF) growth medium. Confluent cells that formed cellular sheets were detached from the culture plate using a micropipette tip. The floating cellular sheet contracted to round clumps of cells (C-MSCs). C-MSCs were maintained in XF-chondro-inductive medium (CIM) and XF-osteo-inductive medium (OIM). The biological and bone-regenerative properties of the generated cellular constructs were assessed in vitro and in vivo. C-MSCs cultured in CIM/OIM formed cartilaginous tissue covered with a mineralized matrix layer, whereas CIM treatment alone induced cartilage with no mineralization. Transplantation of the cartilaginous tissue covered with a mineralized matrix induced more rapid bone reconstruction via endochondral ossification in the severe combined immunodeficiency mouse calvarial defect model than that of cartilage generated using only CIM. These results highlight the potential of C-MSC culture in combination with CIM/OIM to generate cartilage covered with a bone collar-like structure, which can be applied for novel bone-regenerative cell therapy.

Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples

Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide-bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu's parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of <1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate that Ryugu's parent body formed ~2 million years after the beginning of Solar System formation.

Regulation of osteogenesis in bone marrow-derived mesenchymal stem cells via histone deacetylase 1 and 2 co-cultured with human gingival fibroblasts and periodontal ligament cells

OBJECTIVE

This study aimed to determine the regulatory mechanism of bone marrow-derived mesenchymal stem cell (BM-MSC) differentiation mediated by humoral factors derived from human periodontal ligament (HPL) cells and human gingival fibroblasts (HGFs). We analyzed histone deacetylase (HDAC) expression and activity involved in BM-MSC differentiation and determined their regulatory effects in co-cultures of BM-MSCs with HPL cells or HGFs.

BACKGROUND

BM-MSCs can differentiate into various cell types and can, thus, be used in periodontal regenerative therapy. However, the mechanism underlying their differentiation remains unclear. Transplanted BM-MSCs are affected by periodontal cells via direct contact or secretion of humoral factors. Therefore, their activity is regulated by humoral factors derived from HPL cells or HGFs.

METHODS

BM-MSCs were indirectly co-cultured with HPL cells or HGFs under osteogenic or growth conditions and then analyzed for osteogenesis, HDAC1 and HDAC2 expression and activity, and histone H3 acetylation. BM-MSCs were treated with trichostatin A, or their HDAC1 or HDAC2 expression was silenced or overexpressed during osteogenesis. Subsequently, they were evaluated for osteogenesis or the effects of HDAC activity.

RESULTS

BM-MSCs co-cultured with HPL cells or HGFs showed suppressed osteogenesis, HDAC1 and HDAC2 expression, and HDAC phosphorylation; however, histone H3 acetylation was enhanced. Trichostatin A treatment remarkably suppressed osteogenesis, decreasing HDAC expression and enhancing histone H3 acetylation. HDAC1 and HDAC2 silencing negatively regulated osteogenesis in BM-MSCs to the same extent as that achieved by indirect co-culture with HPL cells or HGFs. Conversely, their overexpression positively regulated osteogenesis in BM-MSCs.

CONCLUSION

The suppressive effects of HPL cells and HGFs on BM-MSC osteogenesis were regulated by HDAC expression and histone H3 acetylation to a greater extent than that mediated by HDAC activity. Therefore, regulation of HDAC expression has prospects in clinical applications for effective periodontal regeneration, mainly, bone regeneration.

Contribution of dental health in cardiovascular secondary prevention

Backgrounds

Previous studies have suggested that periodontitis is associated with cardiovascular disease (CVD), partly through exaggerated systematic inflammation through pathogens breaking into the bloodstream and their metabolic products. However, the clinical evidence in the cardiovascular secondary prevention is limited. In addition, there is a paucity of data about the contribution of comprehensively assessed dental health, including dental caries or teeth loss, to CVD incidence. Consequently, current ESC guideline for CVD prevention just briefly refers the contribution of dental health [1].

Objective

To investigate the associations between teeth loss, periodontitis, and dental caries and incident major adverse cardiovascular events (MACE) in patients with existing CVD.

Methods

Patients with known CVD who were admitted to the Department of Cardiology between May 2012 and August 2015 were prospectively, consecutively enrolled. Patients underwent comprehensive dental examinations, including counts of lost teeth, dental caries, and periodontal measurements of clinical attachment loss (CAL), periodontal probing pocket depth (PPD), and bleeding on probing (BOP) by trained periodontists during the hospital stay. We assessed the associations between these dental measures and MACE, defined as a composite of cardiac death, acute myocardial infarction, stroke, and hospital re-admission for worsened congestive heart failure, using multivariate COX proportional hazard models and restricted mean survival time (RMST) analyses. P-values were adjusted by Bonferroni methods.

Results

Among 888 patients included for the present analyses, the mean age was 63.9 (SD: 13.1) years and there were 242 (27.3%) women. During a median follow-up of 4.6 (IQR: 1.4, 6.7) years, incident MACE was confirmed in 142 patients. In multivariate COX proportional hazard models, one more tooth loss was associated with 3 (95% CI: 1, 5) % higher hazard of MACE (adjusted p=0.020). Kaplan-Meier curves showing survival from MACE according to the quartiles of teeth loss were described in Figure 1. Compared with patients with 0 to ≤4 lost teeth, periods free from MACE (95% CI) by 5-years of follow-up were on average shorter by 0.17 (−0.04, 0.37) years, 0.26 (0.04, 0.49) years, and 0.59 (0.34, 0.85) years in patients with 5 to ≤7, 8 to ≤13, and &gt;13 lost teeth, respectively. The RMST differences with varied cutoff years were shown in Figure 2. There were no significant associations between the number of dental caries, CAL, PPD, and BOP and MACE incidence.

Conclusion

In hospitalized patients due to existing cardiovascular diseases, total number of lost teeth was associated with incident MACE. Given that teeth loss is an ultimate consequence of periodontitis or dental caries, the present findings imply that efforts to prevent losing teeth by maintaining dental health would be effective measures for cardiovascular secondary prevention.

Funding Acknowledgement

Type of funding sources: None.

Clumps of mesenchymal stem cells/extracellular matrix complexes directly reconstruct the functional periodontal tissue in a rat periodontal defect model

Periodontitis is an inflammatory disease characterized by tooth-supporting periodontal tissue destruction, including the cementum, periodontal ligament, and alveolar bone. To regenerate the damaged periodontal tissue, mesenchymal stem cells (MSCs) have attracted much scientific and medical attention. Recently, we generated clumps of MSCs/extracellular matrix (ECM) complexes (C-MSCs), which consist of cells and self-produced ECM. C-MSCs can be transplanted into lesion areas without artificial scaffold to induce tissue regeneration. To develop reliable scaffold-free periodontal tissue regenerative cell therapy by C-MSCs, this study investigated the periodontal tissue regenerative capacity of C-MSCs and the behavior of the transplanted cells. Rat bone marrow-derived MSCs were isolated from rat femur. Confluent cells were scratched using a micropipette tip and then torn off. The sheet was rolled to make a three-dimensional round clump of cells, C-MSCs. Then, ten C-MSCs were grafted into a rat periodontal fenestration defect model. To trace the grafted cells in the defect, PKH26-labeled cells were also employed. Micro-CT and histological analyses demonstrated that transplantation of C-MSCs induced successful periodontal tissue regeneration in the rat periodontal defect model. Interestingly, the majority of the cells in the reconstructed tissue, including cementum, periodontal ligaments, and alveolar bone, were PKH26 positive donor cells, suggesting the direct tissue formation by MSCs. This study demonstrates a promising scaffold-free MSCs transplantation strategy for periodontal disease using C-MSCs and offers the significance of multipotency of MSCs to induce successful periodontal tissue regeneration.

Masticatory dysfunction in patients with diabetic neuropathy: A cross-sectional study

Introduction

Chewing well is essential for successful diet therapy and control of blood glucose level in patients with diabetes. In addition, long-term hyperglycemia is a risk factor for microvascular complications, which are the main cause of morbidity and mortality in these patients. Hence, it is plausible that masticatory disorder may be relevant to diabetic microvascular complications which is caused by long-term hyperglycemia. The aim of this study was to investigate whether masticatory disorders are relevant to diabetic microvascular complications.

Methods

This cross-sectional study included 172 patients with type 2 diabetes who underwent educational hospitalization in the Department of Endocrinology and Diabetic Medicine, Hiroshima University Hospital, from April 2016 to March 2020. Masticatory efficiency was determined quantitatively by using the GLUCO SENSOR GS-Ⅱ. Multivariable linear regression models were constructed to examine which factors were related to masticatory efficiency. Statistical significance was defined as a two-sided p value of < 0.05.

Results

According to the bivariable analysis, masticatory efficiency was significantly correlated with duration of diabetes (p = 0. 049), number of remaining teeth (p < 0.0001), the number of moving teeth (p = 0.007) and condition of diabetic neuropathy (p < 0.0001). Moreover, the number of remaining teeth (p < 0.0001) and diabetic neuropathy (p = 0.007) remained significantly correlated with masticatory efficiency in the multivariable analysis.

Conclusions

For the first time, we demonstrated that patients with type 2 diabetes who developed diabetic neuropathy had significantly reduced masticatory efficiency. Effective mastication is an important factor in successful diet therapy for diabetes. To prevent the progression of diabetic complications, especially in patients with diabetic neuropathy, it may be necessary to combine individualized therapies from dentists and nutritionists with consideration for the level of masticatory dysfunction.

Xenotransplantation of cryopreserved human clumps of mesenchymal stem cells/extracellular matrix complexes pretreated with IFN-γ induces rat calvarial bone regeneration

Introduction

Three-dimensional (3D) clumps of mesenchymal stem cells (MSCs)/extracellular matrix (ECM) complexes, composed with cells and self-produced intact ECM, can be grafted into defect areas without artificial scaffold to induce successful bone regeneration. Moreover, C-MSCs pretreated with IFN-γ (C-MSCsγ) increased the immunomodulatory enzyme indoleamine 2,3-dioxygenase (IDO) expression and thereby inhibited T cell activity. Xenotransplantation of human C-MSCsγ suppressed host T cell immune rejection and induced bone regeneration in mice. Besides, we have also reported that C-MSCs retain the 3D structure and bone regenerative property even after cryopreservation. To develop the "off-the-shelf" cell preparation for bone regenerative therapy that is promptly provided when needed, we investigated whether C-MSCsγ can retain the immunosuppressive and osteogenic properties after cryopreservation.

Methods

Confluent human MSCs that had formed on the cellular sheet were scratched using a micropipette tip and then torn off. The sheet was rolled to make a round clump of cells. The round cell clumps were incubated with a growth medium for 3 days, and then C-MSCs were obtained. To generate C-MSCsγ, after 2 days' culture, C-MSCs were stimulated with 50 ng/ml of IFN-γ. Both C-MSCs and C-MSCsγ were cryopreserved for 2 days and then thawed to obtain Cryo-C-MSCs and Cryo-C-MSCsγ, respectively. The biological properties of those cell clumps were assessed in vitro. In addition, to test whether human Cryo-C-MSCsγ attenuates immune rejection to induce bone regeneration, a xenograft study using a rat calvarial defect was performed.

Results

Both IFN-γ pretreatment and cryopreservation process did not affect the 3D structure and cell viability in all human cell clumps. Interestingly, Cryo-C-MSCsγ showed significantly increased IDO mRNA expression equivalent to C-MSCsγ. More importantly, xenotransplantation of human C-MSCsγ and Cryo-C-MSCsγ induced rat calvarial bone regeneration by suppressing rat T cells infiltration and the grafted human cells reduction in the grafted area. Finally, there were no human donor cells in the newly formed bone, implying that the bone reconstruction by C-MSCsγ and Cryo-C-MSCsγ can be due to indirect host osteogenesis.

Conclusion

These findings implied that Cryo-C-MSCsγ can be a promising bone regenerative allograft therapy that can be certainly and promptly supplied on demand.

Pebbles and sand on asteroid (162173) Ryugu: In situ observation and particles returned to Earth

The Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. The mission performed two landing operations to collect samples of surface and subsurface material, the latter exposed by an artificial impact. We present images of the second touchdown site, finding that ejecta from the impact crater was present at the sample location. Surface pebbles at both landing sites show morphological variations ranging from rugged to smooth, similar to Ryugu's boulders, and shapes from quasi-spherical to flattened. The samples were returned to Earth on 6 December 2020. We describe the morphology of >5 grams of returned pebbles and sand. Their diverse color, shape, and structure are consistent with the observed materials of Ryugu; we conclude that they are a representative sample of the asteroid.

Liver Cirrhosis Complicated by Spontaneous Bacterial Peritonitis Caused by the Burkholderia cepacia Complex

A 79-year-old man with underlying alcoholic liver cirrhosis presented with complaints of a fever, abdominal pain, and difficulty walking. A diagnostic work-up revealed liver atrophy and chylous ascites, and spontaneous bacterial peritonitis (SBP) was diagnosed based on the cell and neutrophil counts. The Burkholderia cepacia complex (Bcc) was detected on blood and ascitic fluid cultures. Although broad-spectrum antibiotic therapy was initiated, the infection was difficult to control, and the patient died of multiple organ failure. Bcc is often multidrug-resistant and difficult to treat. SBP caused by Bcc has been rarely reported and may have a serious course, thus necessitating caution.

Real-space modeling for complex structures based on small-angle X-ray scattering

A three-dimensional real-space model has been created for complex hierarchical materials by matching observed and simulated small-angle X-ray scattering patterns. The simulation is performed by arranging the positions of small primary particles and constructing an aggregate structure in a finite-sized cell.

A three-dimensional real-space model has been created for hierarchical materials by matching observed and simulated small-angle X-ray scattering patterns. The simulation is performed by arranging the positions of small primary particles and constructing an aggregate structure in a finite-sized cell. In order to avoid the effect of the finite size of the cell, the cell size is extended to infinity by introducing an asymptotic form of the long-range correlations among the primary particles. As a result, simulations for small-angle X-ray scattering patterns can be performed correctly in the low-wavenumber regime (<0.1 nm⁻¹), allowing the model to handle hundred-nanometre-scale structures composed of primary particles of a few nanometres in size. An aerogel structure was determined using this model, resulting in an excellent match with the experimental scattering pattern. The resultant three-dimensional model can generate cross-sectional images similar to those obtained by transmission electron microscopy, and the calculated pore-size distribution is in accord with that derived from the gas adsorption method.

Endodontic Approach and Periodontal Regenerative Therapy for a Mandibular Right Central Incisor Affected by a Perforation and Cemental Tear

A cemental tear involves complete or incomplete separation of the cementum on the root surface along the cementodentinal junction. Because a cemental tear can lead to periodontal breakdown and mimic endodontic and periodontal lesions, diagnosing clinical cases can be difficult and requires special examinations. A 72-year-old woman presented with a localized periodontal defect on the labial and interproximal surfaces of the mandibular right central incisor. Performing CBCT scans and a biopsy during periodontal surgery allowed definitive diagnosis of a cemental tear and perforation of the site. First, the perforation was repaired with endodontic therapy. Periodontal regenerative therapy using recombinant human fibroblast growth factor-2 (rhFGF-2) was then performed after removing granulomatous tissue and cementum fragments. Examination of the biopsy specimen showed bacterial colonies. This case showed successful clinical and radiographic outcomes at the 18-month follow-up.

Triangle Singularity as the Origin of the a_{1}(1420)

The COMPASS Collaboration experiment recently discovered a new isovector resonancelike signal with axial-vector quantum numbers, the a_{1}(1420), decaying to f_{0}(980)π. With a mass too close to and a width smaller than the axial-vector ground state a_{1}(1260), it was immediately interpreted as a new light exotic meson, similar to the X, Y, Z states in the hidden-charm sector. We show that a resonancelike signal fully matching the experimental data is produced by the decay of the a_{1}(1260) resonance into K^{*}(→Kπ)K[over ¯] and subsequent rescattering through a triangle singularity into the coupled f_{0}(980)π channel. The amplitude for this process is calculated using a new approach based on dispersion relations. The triangle-singularity model is fitted to the partial-wave data of the COMPASS experiment. Despite having fewer parameters, this fit shows a slightly better quality than the one using a resonance hypothesis and thus eliminates the need for an additional resonance in order to describe the data. We thereby demonstrate for the first time in the light-meson sector that a resonancelike structure in the experimental data can be described by rescattering through a triangle singularity, providing evidence for a genuine three-body effect.

Cytokines regulate stemness of mesenchymal stem cells via miR-628-5p during periodontal regeneration

BACKGROUND

Cytokines play key roles in stimulating periodontal regeneration; however, their exact mechanisms of action remain unclear. Mesenchymal stem cells (MSCs) are multipotent cells that have self-renewal abilities and can differentiate into periodontal tissues such as bone, cementum, and periodontal ligaments following transplantation, like periodontal progenitor cells. Here, we used MSCs to identify the regulatory genes induced by periodontal regenerative cytokines.

METHODS

Human MSCs (hMSCs) were cultured under conditions of periodontal regenerative cytokine stimulation or silencing of undifferentiated hMSC transcription factors. To characterize the changes associated with periodontal regenerative cytokine-regulated microRNAs (miRNAs), miRNA, and mRNA expression was evaluated using miRNA arrays and quantitative real-time polymerase chain reaction, respectively. One of the identified miRNAs, miR-628-5p, was then overexpressed or suppressed in hMSCs during osteogenesis; the effect of these changes on osteogenesis was investigated.

RESULTS

Cytokine-stimulated MSCs showed characteristic miRNA profiles and mRNA levels of undifferentiated hMSC transcription factors ETV1, SOX11, and GATA6. Next, we silenced these transcription factors in MSCs and examined the miRNA profiles. The levels of miR-628-5p were decreased upon all cytokine treatments and were increased upon silencing of ETV1, SOX11, and GATA6. Overexpression of miR-628-5p suppressed osteogenesis; however, its inhibition enhanced OPN, ALP, OC, BMP2, and RUNX2 mRNA levels, and bone matrix mineralization, but not OSX mRNA or ALP activity.

CONCLUSIONS

miR-628-5p negatively regulates MSC stemness during periodontal regeneration. Periodontal regenerative cytokines act as miR-628-5p suppressors to support periodontal regeneration. Thus, selection of effective cytokines for different MSCs, based on miRNA profiling, is important for advancing regenerative therapies.

Functional Regulatory Mechanisms Underlying Bone Marrow Mesenchymal Stem Cell Senescence During Cell Passages

Mesenchymal stem cell (MSC) transplantation is an effective periodontal regenerative therapy. MSCs are multipotent, have self-renewal ability, and can differentiate into periodontal cells. However, senescence is inevitable for MSCs. In vitro, cell senescence can be induced by long-term culture with/without cell passage. However, the regulatory mechanism of MSC senescence remains unclear. Undifferentiated MSC-specific transcription factors can regulate MSC function. Herein, we identified the regulatory transcription factors involved in MSC senescence and elucidated their mechanisms of action. We cultured human MSCs (hMSCs) with repetitive cell passages to induce cell senescence and evaluated the mRNA and protein expression of cell senescence-related genes. Additionally, we silenced the cell senescence-induced transcription factors, GATA binding protein 6 (GATA6) and SRY-box 11 (SOX11), and investigated senescence-related signaling pathways. With repeated passages, the number of senescent cells increased, while the cell proliferation capacity decreased; GATA6 mRNA expression was upregulated and that of SOX11 was downregulated. Repetitive cell passages decreased Wnt and bone morphogenetic protein (BMP) signaling pathway-related gene expression. Silencing of GATA6 and SOX11 regulated Wnt and BMP signaling pathway-related genes and affected cell senescence-related genes; moreover, SOX11 silencing regulated GATA6 expression. Hence, we identified them as pair of regulatory transcription factors for cell senescence in hMSCs via the Wnt and BMP signaling pathways.

Cell therapy for medication-related osteonecrosis of the jaw: update on treatment strategies

Bioactive glasses (BAG) are used as bone-graft substitutes in orthopaedic surgery. A specific BAG scaffold was developed by sintering BAG-S53P4 granules. It is hypothesised that this scaffold can be used as a bone substitute to fill bone defects and induce a bioactive membrane (IM) around the defect site. Beyond providing the scaffold increased mechanical strength, that the initial inflammatory reaction and subsequent IM formation can be enhanced by coating the scaffolds with poly(DL-lactide-co-glycolide) (PLGA) is also hypothesised. To study the immunomodulatory effects, BAG-S53P4 (± PLGA) scaffolds were placed on monolayers of primary human macrophage cultures and the production of various pro- and anti-inflammatory cytokines was assessed using reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) and ELISA. To study the osteogenic effects, BAG-S53P4 (± PLGA) scaffolds were cultured with rabbit mesenchymal stem cells and osteogenic differentiation was evaluated by RT-qPCR and matrix mineralisation assays. The scaffold ion release was quantified and the BAG surface reactivity visualised. Furthermore, the pH of culture media was measured. BAG-S53P4 scaffolds had both anti-inflammatory and osteogenic properties that were likely attributable to alkalinisation of the media and ion release from the scaffold. pH change, ion release, and immunomodulatory properties of the scaffold could be modulated by the PLGA coating. Contrary to the hypothesis, the coating functioned by attenuating the BAG surface reactions and subsequent anti-inflammatory properties, rather than inducing an elevated inflammatory response compared to BAG-S53P4 alone. These results further validated the use of BAG-S53P4 (± PLGA) scaffolds as bone substitutes and indicate that scaffold properties can be tailored to a specific clinical need.

Identification of regulatory mRNA and microRNA for differentiation into cementoblasts and periodontal ligament cells

OBJECTIVE

Periodontitis causes periodontal tissue destruction and results in physiological tooth dysfunction. Therefore, periodontal regeneration is ideal therapy for periodontitis. Mesenchymal stem cells (MSCs) are useful for periodontal regenerative therapy as they can differentiate into periodontal cells; however, the underlying regulatory mechanism is unclear. In this study, we attempted to identify regulatory genes involved in periodontal cell differentiation and clarify the differentiation mechanism for effective periodontal regenerative therapy.

BACKGROUND

The cementum and periodontal ligament play important roles in physiological tooth function. Therefore, cementum and periodontal ligament regeneration are critical for periodontal regenerative therapy. Mesenchymal stem cell transplantation can be a common periodontal regenerative therapy because these cells have multipotency and self-renewal ability, which induces new cementum or periodontal ligament formation. Moreover, MSCs can differentiate into cementoblasts. Cementoblast- or periodontal ligament cell-specific proteins have been reported; however, it is unclear how these proteins are regulated. MicroRNA (miRNA) can also act as a key regulator of MSC function. Therefore, in this study, we identified regulatory genes involved in cementoblast or periodontal cell differentiation and commitment.

METHODS

Human MSCs (hMSCs), cementoblasts (HCEM), and periodontal ligament cells (HPL cells) were cultured, and mRNA or miRNA expression was evaluated. Additionally, cementoblast-specific genes were overexpressed or suppressed in hMSCs and their expression levels were investigated.

RESULTS

HCEM and HPL cells expressed characteristic genes, of which we focused on ets variant 1 (ETV1), miR-628-5p, and miR-383 because ETV1 is a differentiation-related transcription factor, miR-628-5p was the second-highest expressed gene in HCEM and lowest expressed gene in HPL cells, and miR-383 was the highest expressed gene in HCEM. miR-628-5p and miR-383 overexpression in hMSCs regulated ETV1 mRNA expression, and miR-383 overexpression downregulated miR-628-5p expression. Moreover, miR-383 suppression decreased miR-383 expression and enhanced ETV1 mRNA expression, but miR-383 suppression also decreased miR-628-5p. Furthermore, silencing of ETV1 expression in hMSCs regulated miR-628-5p and miR-383 expression. Concerning periodontal cell commitment, miR-628-5p, miR-383, and ETV1 regulated the expression of HCEM- or HPL cell-related genes by adjusting the expression of these miRNAs.

CONCLUSION

HCEM and HPL cells show characteristic mRNA and miRNA profiles. In particular, these cells have specific miR-383, miR-628-5p, and ETV1 expression patterns, and these genes interact with each other. Therefore, miR-383, miR-628-5p, and ETV1 are key genes involved in cementogenesis or HPL cell differentiation.

Clinical Outcomes of Post-exposure Prophylaxis following Occupational Exposure to Human Immunodeficiency Virus at Dental Departments of Hiroshima University Hospital

Background

Dental professionals have so many opportunities to use injection needles and sharp instruments during dental treatment that they face an increased risk of needlestick injuries. This retrospective study reports the utilization and clinical outcomes of occupational post-exposure prophylaxis (PEP) with anti-retroviral agents after being potentially exposed to HIV at the dental departments of Hiroshima University Hospital.

Objective

This study reports the utilization and clinical outcomes of occupational post-exposure prophylaxis (PEP) with antiretroviral agents after being potentially exposed to HIV at dental departments of Hiroshima University Hospital.

Methods

Data on the clinical status of HIV-infected source patients and information on HIV-exposed dental professionals from 2007 to 2018 were collected.

Results

Five dentists with an average experience of 5.6 years (1-15 years) were exposed. The averaged CD4-positive cell number and HIV-RNA load were 1176 (768-1898) /μl and less than 20 copies/ml, respectively, in all the patients. Two of the five HIV exposed dentists received PEP. Three months after the exposures, all of their results were negative in HIV antibody/antigen tests.

Conclusion

These data might support the concept of “undetectable equals untransmittable”, although HIV exposure in this study was not through sexual transmission.

Regulation of osteogenesis via miR-101-3p in mesenchymal stem cells by human gingival fibroblasts

INTRODUCTION

Mesenchymal stem cells (MSCs) can differentiate into various types of cells and can thus be used for periodontal regenerative therapy. However, the mechanism of differentiation is still unclear. Transplanted MSCs are, via their transcription factors or microRNAs (miRNAs), affected by periodontal cells with direct contact or secretion of humoral factors. Therefore, transplanted MSCs are regulated by humoral factors from human gingival fibroblasts (HGF). Moreover, insulin-like growth factor (IGF)-1 is secreted from HGF and regulates periodontal regeneration. To clarify the regulatory mechanism for MSC differentiation by humoral factors from HGF, we identified key genes, specifically miRNAs, involved in this process, and determined their function in MSC differentiation.

MATERIALS AND METHODS

Mesenchymal stem cells were indirectly co-cultured with HGF in osteogenic or growth conditions and then evaluated for osteogenesis, undifferentiated MSC markers, and characteristic miRNAs. MSCs had their miRNA expression levels adjusted or were challenged with IGF-1 during osteogenesis, or both of which were performed, and then, MSCs were evaluated for osteogenesis or undifferentiated MSC markers.

RESULTS

Mesenchymal stem cells co-cultured with HGF showed suppression of osteogenesis and characteristic expression of ETV1, an undifferentiated MSC marker, as well as miR-101-3p. Over-expression of miR-101-3p regulated osteogenesis and ETV1 expression as well as indirect co-culture with HGF. IGF-1 induced miR-101-3p and ETV1 expression. However, IGF-1 did not suppress osteogenesis.

CONCLUSIONS

Humoral factors from HGF suppressed osteogenesis in MSCs. The effect was regulated by miRNAs and undifferentiated MSC markers. miR-101-3p and ETV1 were the key factors and were regulated by IGF-1.

A mandibular second molar with a middle mesial root canal

The present case report describes the clinical detection and root canal management of a rare middle mesial canal of a Japanese mandibular second molar by troughing preparation using an operating microscope and cone-beam computed tomography.

Aggressive periodontitis and NOD2 variants

Aggressive periodontitis (AgP) occurs at an early age and causes rapid periodontal tissue destruction. Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) encodes a protein with two caspase recruitment domains and eleven leucine-rich repeats. This protein is expressed mainly in peripheral blood leukocytes and is involved in immune response. NOD2 variants have been associated with increased susceptibility to Crohn's disease, and recently, NOD2 was reported as a causative gene in AgP. The present study aimed to identify potential NOD2 variants in an AgP cohort (a total of 101 patiens: 37 patients with positive family histories and 64 sporadic patients). In the familial group, six patients from two families had a reported heterozygous missense variant (c.C931T, p.R311W). Four patients in the sporadic group had a heterozygous missense variant (c.C1411T, p.R471C), with no reported association to the disease. Overall, two NOD2 variants, were identified in 10% of our AgP cohort. These variants were different from the major variants reported in Crohn's disease. More cases need to be investigated to elucidate the role of NOD2 variants in AgP pathology.

An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime

The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2's Small Carry-on Impactor. The impact produced an artificial crater with a diameter >10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu's surface age.

Periodontal ligament cells regulate osteogenesis via miR-299-5p in mesenchymal stem cells

BACKGROUND

The periodontal ligament contains periodontal ligament cells, which is a heterogeneous cell population, and includes progenitor cells that can differentiate into osteoblasts/cementoblasts. Mesenchymal stem cells (MSCs) can differentiate into various cells and can be used for periodontal regenerative therapy. Therefore, transplanted MSCs can be affected by humoral factors from periodontal ligament cells via the transcription factors or microRNAs (miRNAs) of MSCs. In addition, periostin (POSTN) is secreted from HPL cells and can regulate periodontal regeneration and homeostasis. To clarify the regulatory mechanism of humoral factors from periodontal ligament cells, we attempted to identify key genes, specifically microRNAs, involved in this process.

METHODS

Human MSCs (hMSCs) were indirectly co-cultured with human periodontal ligament cells (HPL cells) and then evaluated for osteogenesis, undifferentiated MSCs markers, and miRNA profiles. Furthermore, hMSCs were indirectly co-cultured with HPL cells in the presence of anti-POSTN monoclonal antibody (anti-POSTN Ab) to block the effect of POSTN from HPL cells, and then evaluated for osteogenesis or undifferentiated MSC markers. Moreover, hMSCs showed alterations in miRNA expression or cultured with HPL were challenged with POSTN during osteogenesis, and cells were evaluated for osteogenesis or undifferentiated MSC markers.

RESULTS

hMSCs co-cultured with HPL cells showed suppressed osteogenesis and characteristic expression of SOX11, an undifferentiated MSC marker, as well as miR-299-5p. Overexpression of miR-299-5p regulated osteogenesis and SOX11 expression as observed with indirect co-culture with HPL cells. Furthermore, MSCs co-cultured with HPL cells were recovered from the suppression of osteogenesis and SOX11 mRNA expression by anti-POSTN Ab. However, POSTN induced miR-299-5p and SOX11 expression, and enhanced osteogenesis.

CONCLUSION

Humoral factors from HPL cells suppressed osteogenesis in hMSCs. The suppressive effect was mediated by miR-299-5p and SOX11 in hMSCs.

Oral environment and taste function of Japanese HIV-infected patients treated with antiretroviral therapy

The aim of the study was to evaluate the oral environment and the taste function of Japanese HIV-infected patients treated with antiretroviral therapy. Their median age of 73 patients taking anti-HIV drugs was 46 years. The median period of taking anti-HIV drugs was 30 months. The oral condition was evaluated by measurement of oral moisture, amount of saliva secretion, the number of oral bacteria, presence of oral candida, a taste test, and the number of missing teeth. The levels of oral moisture and secreted saliva were significantly lower in the HIV-infected group than in the healthy volunteer (control) group. The HIV-infected group showed a more robust decrease in taste sensation than the control group. The number of missing teeth was significantly higher in the HIV-infected group than in the control group. Furthermore, all of the evaluated oral conditions were worse in the HIV-infected patients whose CD4+ T lymphocyte counts were less than 500/mm³ than in the control group. It became clear that the patients taking anti-HIV drugs, especially the CD4+ count < 500/mm3 group, had a deteriorated oral environment and dysgeusia, suggesting that the management of oral hygiene is necessary to maintain oral health, which leads to systemic health.

Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu-A spinning top-shaped rubble pile

The Hayabusa2 spacecraft arrived at the near-Earth carbonaceous asteroid 162173 Ryugu in 2018. We present Hayabusa2 observations of Ryugu's shape, mass, and geomorphology. Ryugu has an oblate "spinning top" shape, with a prominent circular equatorial ridge. Its bulk density, 1.19 ± 0.02 grams per cubic centimeter, indicates a high-porosity (>50%) interior. Large surface boulders suggest a rubble-pile structure. Surface slope analysis shows Ryugu's shape may have been produced from having once spun at twice the current rate. Coupled with the observed global material homogeneity, this suggests that Ryugu was reshaped by centrifugally induced deformation during a period of rapid rotation. From these remote-sensing investigations, we identified a suitable sample collection site on the equatorial ridge.

The surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

The near-Earth asteroid 162173 Ryugu, the target of the Hayabusa2 sample-return mission, is thought to be a primitive carbonaceous object. We report reflectance spectra of Ryugu's surface acquired with the Near-Infrared Spectrometer (NIRS3) on Hayabusa2, to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micrometers was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, which is consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes

The near-Earth carbonaceous asteroid 162173 Ryugu is thought to have been produced from a parent body that contained water ice and organic molecules. The Hayabusa2 spacecraft has obtained global multicolor images of Ryugu. Geomorphological features present include a circum-equatorial ridge, east-west dichotomy, high boulder abundances across the entire surface, and impact craters. Age estimates from the craters indicate a resurfacing age of [Formula: see text] years for the top 1-meter layer. Ryugu is among the darkest known bodies in the Solar System. The high abundance and spectral properties of boulders are consistent with moderately dehydrated materials, analogous to thermally metamorphosed meteorites found on Earth. The general uniformity in color across Ryugu's surface supports partial dehydration due to internal heating of the asteroid's parent body.

Routine Referral by Urologists Increase Opportunities for Corneal Donation

BACKGROUND

The levels of corneal donation are insufficient to meet the demand for corneal transplantation in Japan. To overcome this problem, we started to routinely mention the possibility of corneal donation to the families of patients who died in our hospital's Urology Department in February 2008. In this study, we evaluated the effectiveness of this approach.

METHODS

We retrospectively reviewed the medical records of the patients who died in the Department of Urology, St. Marianna University School of Medicine Hospital, and analyzed the patients' characteristics and information about corneal donation.

RESULTS

In total, 211 patients died in our department between February 2008 and March 2017, and 155 patients were medically suitable corneal donors. We mentioned the possibility of corneal donation to 129 (83.2%) families, and 29 (18.7%) families agreed. Three families subsequently withdrew their consent. Finally, 26 (16.8%) of the families that were approached about corneal donation by urologists agreed to donate their relatives' corneas. Another 2 families voluntarily offered to donate their relatives' corneas. Thus, 28 (18.1%) of 155 medically suitable donors donated their corneas for transplantation. Twenty-six (92.8%) donors were 60 years or older and all donors were affected with malignant genitourinary tumors. Fifty-four (96.4%) corneas were successfully transplanted into recipients.

CONCLUSIONS

Even elderly patients who die of solid carcinoma can be an important source of corneal donors. In this study, we showed that routine referral by urologists increased corneal donation. If this approach were adopted by other departments, it might further increase the number of corneal donations.

Type I collagen deposition via osteoinduction ameliorates YAP/TAZ activity in 3D floating culture clumps of mesenchymal stem cell/extracellular matrix complexes

Background

Three-dimensional (3D) floating culture clumps of mesenchymal stem cell (MSC)/extracellular matrix (ECM) complexes (C-MSCs) consist of cells and self-produced ECM. Previous studies have demonstrated that C-MSCs can be transplanted into bony lesions without an artificial scaffold to induce bone regeneration. Moreover, osteoinductive medium (OIM)-treated C-MSCs (OIM-C-MSCs) have shown rapid and increased new bone formation in vivo. To apply OIM-C-MSCs for novel bone regenerative cell therapy, their cellular properties at the molecular level must be elucidated. The transcriptional co-activators yes-associated protein/transcriptional co-activator with PDZ-binding motif (YAP/TAZ) have been recognized as key players in the mechanotransduction cascade, controlling cell lineage commitment in MSCs. It is plausible that 3D C-MSCs/OIM-C-MSCs cultured in floating conditions could provide distinct microenvironments compared to conventional 2D culture systems and thereby induce unique mechanotransduction cascades. Therefore, this study investigated the YAP/TAZ activity in 3D-cultured C-MSCs/OIM-C-MSCs in floating conditions.

Methods

Human bone marrow-derived MSCs were cultured in growth medium supplemented with ascorbic acid. To obtain C-MSCs, confluent cells that had formed on the cellular sheet were scratched using a micropipette tip and were then torn off. The sheet was rolled to make round clumps of cells. Then, YAP/TAZ activity, filamentous actin (F-actin) integrity, collagen type I (COL1) production, and the differentiation potency in 3D floating culture C-MSCs/OIM-C-MSCs were analyzed.

Results

C-MSCs cultured in floating conditions lost their actin cytoskeleton to downregulate YAP/TAZ activity, which directed cells to undergo adipogenesis/chondrogenesis. OIM treatment induced abundant COL1 deposition, which facilitated Intβ1-dependent actin fiber formation and YAP/TAZ activity to elevate the expression levels of osteogenic master transcriptional factor runt-related transcription factor 2 (RUNX2) mRNA in C-MSCs. Importantly, elevation of YAP/TAZ activity via OIM was associated with COL1 deposition and F-actin integrity, suggesting a positive feedback loop in OIM-C-MSCs.

Conclusion

These findings suggest that OIM-C-MSCs, which form a unique microenvironment that maintains high YAP/TAZ activity, can serve as better candidates for bone regenerative cell therapy than C-MSCs.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1085-9) contains supplementary material, which is available to authorized users.