Delayed osteoblast differentiation and altered inflammatory response around implants placed in incisor sockets of type 2 diabetic rats

Effect of Insulin on Bone Formation Ability of Rat Alveolar Bone Marrow Mesenchymal Stem Cells

The alveolar bone marrow mesenchymal stem cells (ABM-MSCs) play an important role in oral bone healing and regeneration. Insulin is considered to improve impaired oral bones due to local factors, systemic factors and pathological conditions. However, the effect of insulin on bone formation ability of ABM-MSCs still needs to be elucidated. The aim of this study was to determine the responsiveness of rat ABM-MSCs to insulin and to explore the underlying mechanism. We found that insulin promoted ABM-MSCs proliferation in a concentration-dependent manner, in which 10-6 M insulin exerted the most significant effect. 10-6 M insulin significantly promoted the type I collagen (COL-1) synthesis, alkaline phosphatase (ALP) activity, osteocalcin (OCN) expression, and mineralized matrix formation in ABM-MSCs, significantly enhanced the gene and protein expressions of intracellular COL-1, ALP, and OCN. Acute insulin stimulation significantly promoted insulin receptor (IR) phosphorylation, IR substrate-1 (IRS-1) protein expression, and mammalian target of rapamycin (mTOR) phosphorylation, but chronic insulin stimulation decreased these values, while inhibitor NT219 could attenuate these responses. When seeded on β-tricalcium phosphate (β-TCP), ABM-MSCs adhered and grew well, during the 28-day culture period, ABM-MSCs+β-TCP +10-6 M insulin group showed significantly higher extracellular total COL-1 amino-terminus prolongation peptide content, ALP activity, OCN secretion, and Ca and P concentration. When implanted subcutaneously in severe combined immunodeficient mice for 1 month, the ABM-MSCs+β-TCP +10-6 M insulin group obtained the most bone formation and blood vessels. These results showed that insulin promoted the proliferation and osteogenic differentiation of ABM-MSCs in vitro, and enhance osteogenesis and angiogenesis of ABM-MSCs in vivo. Inhibition studies demonstrated that the insulin-induced osteogenic differentiation of ABM-MSCs was dependent of insulin/mTOR signaling. It suggests that insulin has a direct anabolic effect on ABM-MSCs.

P53 negatively regulates the osteogenic differentiation in jaw bone marrow MSCs derived from diabetic osteoporosis

Patients with diabetic osteoporosis (DOP) often suffer from poor osseointegration of artificial implants, which is a challenge that affects implant outcomes. The osteogenic differentiation ability of human jaw bone marrow mesenchymal stem cells (JBMMSCs) is the key to implant osseointegration. Studies have shown that the microenvironment of hyperglycemia affects the osteogenic differentiation of mesenchymal stem cells (MSC), but the mechanism is still unclear. Therefore, the aim of this study was to isolate and culture JBMMSCs from surgically derived bone fragments from DOP patients and control patients to investigate the differences in their osteogenic differentiation ability and to elucidate its mechanisms. The results showed that the osteogenic ability of hJBMMSCs was significantly decreased in the DOP environment. Mechanism study showed that the expression of senescence marker gene P53 was significantly increased in DOP hJBMMSCs compared to control hJBMMSCs according to RNA-sequencing result. Further, DOP hJBMMSCs were found to display significant senescence using β-galactosidase staining, mitochondrial membrane potential and ROS assay, qRT-PCR and WB analysis. Overexpression of P53 in hJBMMSCs, knockdown of P53 in DOP hJBMMSCs, and knockdown followed by overexpression of P53 significantly affected the osteogenic differentiation ability of hJBMMSCs. These results suggest that MSC senescence is an important reason for decreasing osteogenic capacity in DOP patients. P53 is a key target in regulating hJBMMSCs aging, and knocking down P53 can effectively restore the osteogenic differentiation ability of DOP hJBMMSCs and promote osteosynthesis in DOP dental implants. It provided a new idea to elucidate the pathogenesis and treatment of diabetic bone metabolic diseases.

The trajectory of osteoblast progenitor cells in patients with type 2 diabetes and the predictive model for their osteogenic differentiation ability

The fate of osteoprogenitor cells along with the progression of type 2 diabetes (T2DM) and factors determining the fate of those cells remains to be elucidated. This cross-sectional study included 18 normoglycemic, 27 prediabetic, and 73 T2DM to determine osteogenic differentiation across the continuum of dysglycemia and to construct a model to predict the fate of osteoprogenitor cells. This study demonstrated a preserved osteogenic differentiation ability of peripheral blood-derived mononuclear cells (PBMC) isolated from normoglycemic and prediabetic but a progressive decline in their osteogenic differentiation during the progression of T2DM. The rate of osteogenic differentiation rapidly declined by 4-7% annually during the first 10 years of diabetes and then slowed down. A predictive model composed of three independent risk factors, including age, duration of diabetes, and glomerular filtration rate, demonstrated an AuROC of 0.834. With a proposed cut-off of 21.25, this model had 72.0% sensitivity, 87.5% specificity, and 78.9% accuracy in predicting the fate of osteoprogenitor cells. In conclusion, this study provided a perspective on the osteogenic differentiation ability of the osteoprogenitor cells across a continuum of dysglycemia and a predictive model with good diagnostic performance for the prediction of the fate of osteoprogenitor cells in patients with T2DM.

Pyroptosis in bone loss

Pyroptosis could be responsible for the bone loss from bone metabolic diseases, leading to the negative impact on people's health and life. It has been shown that osteoclasts, osteoblasts, macrophages, chondrocytes, periodontal and gingival cells may be involved in bone loss linked with pyroptosis. So far, the involved mechanisms have not been fully elucidated. In this review, we introduced the related cells involved in the pyroptosis associated with bone loss and summarized the role of these cells in the bone metabolism during the process of pyroptosis. We also discuss the clinical potential of targeting mechanisms in the osteoclasts, osteoblasts, macrophages, chondrocytes, periodontal and gingival cells touched upon pyroptosis to treat bone loss from bone metabolic diseases as well as the challenges of avoiding potential side effects and producing efficient treatment methods.

Metformin enhances the osteogenic activity of rat bone marrow mesenchymal stem cells by inhibiting oxidative stress induced by diabetes mellitus: an in vitro and in vivo study

PURPOSE

The purpose of this study was to determine whether metformin (MF) could alleviate the expresssion of reactive oxygen species (ROS) and improve the osteogenic ability of bone marrow mesenchymal stem cells derived from diabetic rats (drBMSCs) in vitro, and to evaluate the effect of MF on the ectopic osteogenesis of drBMSCs in a nude mouse model in vivo.

METHODS

BMSCs were extracted from normal and diabetic rats. In vitro, a cell viability assay (Cell Counting Kit-8), tests of alkaline phosphatase (ALP) activity, and western blot analysis were first used to determine the cell proliferation and osteogenic differentiation of drBMSCs that were subjected to treatment with different concentrations of MF (0, 50, 100, 200, 500 μM). The cells were then divided into 5 groups: (1) normal rat BMSCs (the BMSCs derived from normal rats group), (2) the drBMSCs group, (3) the drBMSCs + Mito-TEMPO (10 μM, ROS scavenger) group, (4) the drBMSCs + MF (200 μM) group, and (5) the drBMSCs + MF (200 μM) + H₂O₂ (50 μM, ROS activator) group. Intracellular ROS detection, a senescence-associated β-galactosidase assay, ALP staining, alizarin red staining, western blotting, and immunofluorescence assays were performed to determine the effects of MF on oxidative stress and osteogenic differentiation in drBMSCs. In vivo, the effect of MF on the ectopic osteogenesis of drBMSCs was evaluated in a nude mouse model.

RESULTS

MF effectively reduced ROS levels in drBMSCs. The cell proliferation, ALP activity, mineral deposition, and osteogenic-related protein expression of drBMSCs were demonstrably higher in the MF-treated group than in the non-MF-treated group. H₂O₂ inhibited the effects of MF. In addition, ectopic osteogenesis was significantly increased in drBMSCs treated with MF.

CONCLUSIONS

MF promoted the proliferation and osteogenic differentiation of drBMSCs by inhibiting the oxidative stress induced by diabetes and enhenced the ectopic bone formation of drBMSCs in nude mice.

Assessment of Bone Mineral Density in Type 2 Diabetes: A Cone Beam Computed Tomography (CBCT) Study

Introduction

The main purpose of the study was to assess and compare bone mineral density (BMD) at prospective implant sites in the mandible in type 2 diabetes mellitus (T2DM) and non-diabetic patients using cone beam computed tomography (CBCT).

Material and methodology

A total of 40 patients were included in this type of cross-sectional study. They were divided into two groups, A and B, according to their haemoglobin A1c values. Group A consisted of patients with HbA1c between the range of 6.1%-8% and group B had patients with no history of T2DM. CBCT scans were made of the mandibular arches of both the patients to evaluate the BMD at lingual and buccal cortical plates and the trabecular regions in two successive slices with the assistance of PlanMeca Romexis software (PlanMeca Romexis®, Helsinki, Finland). The Shapiro-Wilk test was used to determine the normality of continuous data. The Mann-Whitney U test was used to compare the groups.

Results

There were no differences that were statistically significant between the two cohorts according to the Mann-Whitney U test at buccal cortical plate points 1 and 2. However, the diabetes group's mean bone density at implant sites-A, B, C, D, and E at trabeculae points 1 and 2 was considerably (7p>0.001) lower than the non-diabetic groups. The mean bone density of the diabetes group was marginally but significantly (p=0.009) lower than the non-diabetic group at lingual cortical plates.

Conclusion

Individuals with type 2 diabetes mellitus show significantly lower bone mineral density in the lingual cortical plate and trabecular region, however, implant therapy can be performed with certain mentioned guidelines in such regions. In the buccal cortical region, the bone mineral density is seen to be unaffected.

High glucose-induced inhibition of osteoblast like MC3T3-E1 differentiation promotes mitochondrial perturbations

Diabetes mellitus is a metabolic disorder that causes health concerns worldwide. Patients with diabetes exhibit multisystemic symptoms, including loss of bone quality over time. The progressive deterioration of bone promotes failure to withstand damage and increases the risk of fractures. Much of the molecular and metabolic mechanism(s) in diabetic bone remains unclear. In vitro studies suggest that hyperglycemia inhibits mineralization, affecting bone formation and function. In this study, inhibition of osteoblast differentiation was induced using hyperglycemia to assess whether high glucose promotes mitochondrial impairment along with altered bone matrix formation. It was hypothesized that bone energy metabolism would be altered in these cells as calcium deposition, a key phase for bone function, is suppressed. Early passages of osteoblast like MC3T3-E1 cells were differentiated under normal and high glucose conditions. To investigate osteoblast differentiation, we quantified calcium accumulation by alizarin red staining and analyzed immunoblots of key proteins. To assess mitochondrial function, we quantified mitochondrial DNA (mtDNA), detected expression and function of key proteins from the Tricarboxylic (TCA) cycle, measured mitochondrial respiration, and fuel oxidation of alternative nutrients. Results confirmed previous work showing that mineralization was inhibited and AKT expression was reduced in high glucose-treated bone cells. Unexpectedly, high glucose-treated osteoblast cells utilize both mitochondrial respiration and glycolysis to maintain energy demands with partial help of fatty acid for reliance of baseline bioenergetics. These metabolic shifts suggest that hyperglycemia maintain bone metabolic needs in an early differentiated state concurrent to the inhibition in bone matrix formation.

Physically Cross-Linked DNA Hydrogel-Based Sustained Cytokine Delivery for In Situ Diabetic Alveolar Bone Rebuilding

The development of a biodegradable and shape-adaptable bioscaffold that can enhance local cytokine retention and bioactivity is essential for the application of immunotherapy in periodontal diseases. Here, we report a biodegradable, anti-inflammatory, and osteogenic ILGel that uses a physically cross-linked DNA hydrogel as a soft bioscaffold for the long-term sustained release of cytokine interleukin-10 (IL-10) to accelerate diabetic alveolar bone rebuilding. Porous microstructures of ILGel favored the encapsulation of IL-10 and maintained IL-10 bioactivity for at least 7 days. ILGel can be gradually degraded or hydrolyzed under physiological conditions, avoiding the potential undesired side effects on dental tissues. Long-term sustained release of bioactive IL-10 from ILGel not only promoted M2 macrophage polarization and attenuated periodontal inflammation but also triggered osteogenesis of mesenchymal stem cells (MSCs), leading to accelerated alveolar bone formation and healing of alveolar bone defects under diabetic conditions in vivo. ILGel treatment significantly accelerated the defect healing rate of diabetic alveolar injury up to 93.42 ± 4.6% on day 21 post treatment compared to that of free IL-10 treatment (63.30 ± 7.39%), with improved trabecular architectures. Our findings imply the potential application of the DNA hydrogel as the bioscaffold for cytokine-based immunotherapy in diabetic alveolar bone injury and other periodontal diseases.

Latest Trends in Surface Modification for Dental Implantology: Innovative Developments and Analytical Applications

An increase in the world population and its life expectancy, as well as the ongoing concern about our physical appearance, have elevated the relevance of dental implantology in recent decades. Engineering strategies to improve the survival rate of dental implants have been widely investigated, focusing on implant material composition, geometry (usually guided to reduce stiffness), and interface surrounding tissues. Although efforts to develop different implant surface modifications are being applied in commercial dental prostheses today, the inclusion of surface coatings has gained special interest, as they can be tailored to efficiently enhance osseointegration, as well as to reduce bacterial-related infection, minimizing peri-implantitis appearance and its associated risks. The use of biomaterials to replace teeth has highlighted the need for the development of reliable analytical methods to assess the therapeutic benefits of implants. This literature review considers the state-of-the-art strategies for surface modification or coating and analytical methodologies for increasing the survival rate for teeth restoration.

Abnormal macrophage polarization impedes the healing of diabetes-associated tooth sockets

Patients with poorly controlled type 2 diabetes mellitus (T2DM) often experience delayed tooth extraction socket (TES) healing. Delayed healing is often associated with an aberrant inflammatory response orchestrated by either M1 pro-inflammatory or M2 anti-inflammatory macrophages. However, the precise mechanism for the attenuated TES healing remains unclear. Here we used diet-induced T2DM mice as a model to study TES. Compared with the control group, the T2DM group showed delayed TES healing and diminished expression of osteogenic and angiogenic genetic profiles. Meanwhile, we detected a more inflammatory profile, with more M1 macrophages and TNF-α expression and less M2 macrophages and PPARγ expression, in TES in the T2DM group when compared to control mice. In vitro co-culture models showed that M1 macrophages inhibited the osteogenic capacity of bone marrow stromal cells and the angiogenic capacity of endothelial cells while M2 macrophages showed an opposite effect. In addition, we constructed a gelatin/β-TCP scaffold with IL-4 to induce macrophage transformation towards M2 polarization. In vitro analyses of the hybrid scaffold revealed sustained release of IL-4 and a phenotype switch to M2 macrophages. Finally, we demonstrated that sustained IL-4 release significantly increased expression of osteogenic and angiogenic genetic profiles and improved TES healing in T2DM mice. Together, we report that increased M1 and decreased M2 macrophage polarization may be responsible for delayed TES healing in T2DM patients through abnormal expression of TNF-α and PPARγ. This imbalance negatively influences osteogenesis and angiogenesis, two of the most important biological factors in bone wound healing. Enhancing M2 macrophage polarization with IL-4 delivery system may represent a potential strategy for promoting the healing of TES in T2DM patients.

Ex vivo Bone Models and Their Potential in Preclinical Evaluation

PURPOSE OF REVIEW

Novel therapies for damaged and diseased bone are being developed in a preclinical testing process consisting of in vitro cell experiments followed by in vivo animal studies. The in vitro results are often not representative of the results observed in vivo. This could be caused by the complexity of the natural bone environment that is missing in vitro. Ex vivo bone explant cultures provide a model in which cells are preserved in their native three-dimensional environment. Herein, it is aimed to review the current status of bone explant culture models in relation to their potential in complementing the preclinical evaluation process with specific attention paid to the incorporation of mechanical loading within ex vivo culture systems.

RECENT FINDINGS

Bone explant cultures are often performed with physiologically less relevant bone, immature bone, and explants derived from rodents, which complicates translatability into clinical practice. Mature bone explants encounter difficulties with maintaining viability, especially in static culture. The integration of mechanical stimuli was able to extend the lifespan of explants and to induce new bone formation. Bone explant cultures provide unique platforms for bone research and mechanical loading was demonstrated to be an important component in achieving osteogenesis ex vivo. However, more research is needed to establish a representative, reliable, and reproducible bone explant culture system that includes both components of bone remodeling, i.e., formation and resorption, in order to bridge the gap between in vitro and in vivo research in preclinical testing.

Osteopenic effects of high-fat diet-induced obesity on mechanically induced alveolar bone remodeling

OBJECTIVES

The aim of the study was to investigate the effect of obesity on the tissue and molecular reactions of alveolar bone in response to orthodontic force and its underlying mechanisms.

METHODS

Sixty-four rats were randomly divided into normal diet (ND) and high-fat diet (HFD) groups for eight weeks of dietary treatment. OTM was induced using nickel-titanium springs between the upper left first molar and incisor. After 1, 3, 7, and 14 days of OTM, the maxillary alveolar bone and gingival tissues were harvested and analyzed.

RESULTS

Compared with the ND rats, the HFD rats had greater OTM distance, serum levels of tartrate-resistant acid phosphatase (TRAP), and tumor necrosis factor α (TNF-α), as well as significant alveolar bone loss and bone architecture deterioration on both the compression and tension sides (p < .05 for all). This response was linked to the increased osteoclast numbers and functional activity and decreased osteoblast activity in the periodontal ligament, gingival tissue, and alveolar bone.

CONCLUSIONS

HFD-induced obesity promoted mechanically induced alveolar bone remodeling and detrimental changes in alveolar bone microstructure by increasing osteoclastogenesis and regulating inflammatory cytokine expression. The increased alveolar bone remodeling in the obese rats lead to an accelerated OTM.

Impact of hyperglycemia and treatment with metformin on ligature-induced bone loss, bone repair and expression of bone metabolism transcription factors

This study evaluated the influence of type 2 diabetes mellitus on bone loss, bone repair and cytokine production in hyperglycemic rats, treated or not with metformin. The animals were distributed as follow: Non-Hyperglycemic (NH), Non Hyperglycemic with Ligature (NH-L), Treated Non Hyperglycemic (TNH), Treated Non Hyperglycemic with Ligature Treated (TNH-L), Hyperglycemic (H), Treated Hyperglycemic (TH), Hyperglycemic with Ligature (H-L), Treated Hyperglycemic with Ligature (TH-L). At 40th day after induction of hyperglycemia, the groups NH-L, TNH-L, H-L, TH-L received a ligature to induce periodontitis. On the 69th, the TNH, TNH-L, TH, TH-L groups received metformin until the end of the study. Bone repair was evaluated at histometric and the expression levels of Sox9, RunX2 and Osterix. Analysis of the ex-vivo expression of TNF-α, IFN-γ, IL-12, IL-4, TGF-β, IL-10, IL-6 and IL-17 were also evaluated. Metformin partially reverse induced bone loss in NH and H animals. Lower OPG/RANKL, increased OCN and TRAP expression were observed in hyperglycemic animals, and treatment with metformin partially reversed hyperglycemia on the OPG/RANKL, OPN and TRAP expression in the periodontitis. The expression of SOX9 and RunX2 were also decreased by hyperglycemia and metformin treatment. Increased ex vivo levels of TNF-α, IL-6, IL-4, IL-10 and IL-17 was observed. Hyperglycemia promoted increased IL-10 levels compared to non-hyperglycemic ones. Treatment of NH with metformin was able to mediate increased levels of TNF-α, IL-10 and IL-17, whereas for H an increase of TNF-α and IL-17 was detected in the 24- or 48-hour after stimulation with LPS. Ligature was able to induce increased levels of TNF-α and IL-17 in both NH and H. This study revealed the negative impact of hyperglycemia and/or treatment with metformin in the bone repair via inhibition of transcription factors associated with osteoblastic differentiation.

The Impact of Curcumin on Bone Osteogenic Promotion of MC3T3 Cells under High Glucose Conditions and Enhanced Bone Formation in Diabetic Mice

Diabetic osteoporosis (DOP) is characterized by impaired bone microstructure and reduced bone density resulting from high glucose levels. Curcumin (CURC) is extensively applied in the treatment of inflammation-associated diseases. However, the effect of curcumin on bone metabolism in diabetic osteoporosis is unclear. Therefore, this study investigated the optimal concentration of curcumin on enhancing osteogenesis in diabetic osteoporosis. Osteoblasts were treated with a high or low concentration of curcumin under a series of concentrations of high-glucose conditions. Type 2 diabetic mice were intervened with curcumin. Cell proliferation, apoptosis, and osteogenesis-related gene expressions were evaluated by CCK-8, flow cytometry, and real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR). Bone formation was evaluated by histological staining. The findings revealed that curcumin suppressed apoptosis and enhanced proliferation and osteogenesis-related gene expressions of osteoblasts under high glucose concentrations (p < 0.05). The histological sections displayed reduced bone destruction and increased the growth rate of trabecular bone and the bone density of diabetic mice treated with curcumin, compared to diabetic mice. These results showed that curcumin could reverse the harmful effects of diabetic osteoporosis in a dose-dependent manner, and 10 μmol/L was regarded as the optimal concentration, which supports the potential use of curcumin for bone regeneration under high glucose concentrations.

Current Knowledge Regarding the Interaction Between Oral Bone Metabolic Disorders and Diabetes Mellitus

Diabetes mellitus, a major chronic disease affecting human health, has been increasing in prevalence in recent years. Diabetes mellitus can cause bone metabolic disorders in patients, leading to osteoporosis, a higher risk of traumatic fracture, and other bone diseases. Bone metabolic disorders in the oral cavity principally manifest as periodontitis, loss of alveolar bone, and failure of implant osseointegration. In recent years, numerous studies have shown that there is a complex interaction between bone metabolic disorders and diabetes mellitus. This paper reviews the adverse effects of diabetes on oral bone metabolism disorders such as alveolar osteoporosis and bone loss in patients with periodontitis, discusses the potential mechanisms of diabetic bone loss, and suggests potential ways to prevent and treat oral bone loss in patients with diabetes mellitus.

Effects of high glucose conditions on the expansion and differentiation capabilities of mesenchymal stromal cells derived from rat endosteal niche

Background

Mesenchymal stromal cells in the endosteal niche lining compact bone (CB-MSCs) represent a heterogeneous population, all of which contribute to bone repair and remodelling. Hyperglycaemia associated with type 2 diabetes mellitus (T2DM) can delay and impair the bone healing process. Therefore, this study investigated the influences of high (25 mM) glucose conditions on CB-MSC populations isolated from male Wistar rats, versus normal (5.5 mM) glucose conditions; in terms of proliferation (population doublings, PDs), senescence characteristics, stem cell marker expression, colony forming efficiencies (CFEs); and osteogenic/adipogenic differentiation, following extended culture in vitro.

Results

CB-MSCs under both normoglycaemic and hyperglycaemic conditions demonstrated similar morphologies and rapid exponential growth to >300PDs, although high glucose conditions promoted more rapid and persistent proliferation beyond ~50PDs, with few indications of senescence. Limited senescence was confirmed by minimal SA-β-galactosidase staining, low senescence marker (p53, p21^waf1, p16^INK4a) expression and positive telomere maintenance marker (rTERT, TR) expression. However, telomere lengths varied throughout culture expansion, with hyperglycaemia significantly reducing telomere lengths at PD50 and PD200. Furthermore, CB-MSCs expanded in normal and high glucose conditions remained non-transformed, exhibiting similar MSC (CD73/CD90/CD105), multipotency (CD146) and embryonic (Slug, Snail) markers throughout extended culture, but negligible hematopoietic (CD34/CD45) or pluripotency (Nanog, Oct4) markers. Hyperglycaemia significantly increased CFEs at PD50 and PD100, which decreased at PD200. CB-MSC osteogenic differentiation was also inhibited by hyperglycaemia at PD15, PD100 and PD200, but not at PD50. Hyperglycaemia inhibited CB-MSC adipogenic differentiation to a lesser extent at PD15 and PD50, with reduced adipogenesis overall at PD100 and PD200.

Conclusion

This study demonstrates the limited negative impact of hyperglycaemia on the proliferative and stem cell characteristics of heterogeneous CB-MSC populations, although minor sub-population(s) appear more susceptible to these conditions leading to impaired osteogenic/adipogenic differentiation capabilities. Such findings potentially highlight the impact of hyperglycaemia on CB-MSC bone repair capabilities in situ.

[Effect of Angelica sinensis polysaccharide on the osteogenic differentiation of bone marrow mesenchymal stem cells of rats with high glucose levels]

OBJECTIVE

This study aims to evaluate the effect of Angelica sinensis polysaccharide (ASP) on the osteogenic differentiation of the bone marrow mesenchymal stem cells (BMSCs) of rats with high glucose levels.

METHODS

Rat BMSCs were isolated and identified by osteogenic and adipogenic differentiation. Then, the BMSCs were divided into three groups as follows: normal control group (5.5 mmol·L⁻¹ glucose), high glucose group (25.5 mmol·L⁻¹ glucose), and ASP+high glucose group (25.5 mmol·L⁻¹ glucose +40 mg·L⁻¹ ASP). The proliferation activities of the BMSCs were detected by CCK8. Alizarin red staining, and alkaline phosphatase activity were used in the examination of osteogenic activity. Quantitative real time-polymerase chain reaction was used to detect the expression levels of the osteogenic genes (Runx2, Osx, OCN, Col-Ⅰ) and the key factors of Wnt/β-catenin signal pathway (CyclinD1, β-catenin). In vivo, a type 2 diabetes rat model was established. The rats were divided into three groups, namely, the normal control group (normal rats), diabetes group (diabetic rats), diabetes+ASP group (diabetic rats, ASP feeding). Then, the tibia bone defect was established. The repair of bone defects in each group was observed through histological examination.

RESULTS

The proliferation of BMSCs was higher in the high glucose group and ASP+high glucose group than in the normal control group (P<0.05). No significant difference was observed between the high glucose group and ASP+high glucose group (P>0.05). The number of calcium nodules of BMSCs; alkaline phosphatase activity; and the mRNA expression of Runx2, OCN, Osx, Col-Ⅰ, CyclinD1, β-catenin in the high glucose group were lower than those in the normal control and ASP+high glucose groups (P<0.05). No significant difference was observed between the normal control and ASP+high glucose groups (P>0.05). The bone mass was significantly lower in the bone defect of the diabetes group than in the bone defect of the normal control or diabetes+ASP group (P<0.05). No statistical difference was found between the normal control and diabetes+ASP groups (P>0.05).

CONCLUSIONS

ASP can promote the osteogenic differentiation of rat BMSCs under high glucose culture and induce bone regeneration in rats with type 2 diabetes. These features may be related to the activation of the Wnt/β-catenin signaling pathway.

Suppression of NLRP3 inflammasome improves alveolar bone defect healing in diabetic rats

Background

Excessive inflammatory response under hyperglycemia can impair alveolar bone defect healing under diabetic conditions. NLRP3 (NACHT [nucleotide-binding oligomerization], LRR [leucine-rich repeat], and PYD [pyrin domain] domains-containing protein 3) inflammasome has been considered to play a crucial role in the inflammatory response, but its correlation with the impaired alveolar bone repair in diabetes still remains unclarified. The objective of the current study is to investigate the effect of NLRP3 inflammasome inhibition by a lentiviral short hairpin RNA (shRNA) targeting NLRP3 on alveolar bone defect healing in diabetic rats.

Methods

Diabetes was induced in rats by high-fat diet and streptozotocin injection, and alveolar bone defects in both maxillae were created by surgery. Then, the lentiviral shRNA targeting NLRP3 was applied in the defect. Eight weeks after surgery, the alveolar bone regeneration was examined using hematoxylin and eosin (H&E) staining, and the gene expression in the bone healing site was detected using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) analysis and western blot analysis.

Results

H&E staining showed that treatment with lentiviral shRNA targeting NLRP3 could increase the bone regeneration score in the alveolar bone defect of diabetic rats. Additionally, qRT-PCR analysis and western blot analysis of the bone defect demonstrated that this shRNA inhibited the expression of NLRP3, apoptosis-associated speck-like protein containing a CARD, caspase-1, and proinflammatory cytokine interleukin-1β and increased the expression of osteogenic markers Runt-related transcription factor 2 and osteocalcin.

Conclusions

Our findings suggested that inhibition of NLRP3 inflammasome could improve alveolar bone defect healing in diabetic rats. The beneficial effect may correlate with reduced proinflammatory cytokine production and increased osteogenic gene expression in hyperglycemia.

Electronic supplementary material

The online version of this article (10.1186/s13018-019-1215-9) contains supplementary material, which is available to authorized users.

Cellular biology of fracture healing

The biology of bone healing is a rapidly developing science. Advances in transgenic and gene-targeted mice have enabled tissue and cell-specific investigations of skeletal regeneration. As an example, only recently has it been recognized that chondrocytes convert to osteoblasts during healing bone, and only several years prior, seminal publications reported definitively that the primary tissues contributing bone forming cells during regeneration were the periosteum and endosteum. While genetically modified animals offer incredible insights into the temporal and spatial importance of various gene products, the complexity and rapidity of healing-coupled with the heterogeneity of animal models-renders studies of regenerative biology challenging. Herein, cells that play a key role in bone healing will be reviewed and extracellular mediators regulating their behavior discussed. We will focus on recent studies that explore novel roles of inflammation in bone healing, and the origins and fates of various cells in the fracture environment. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Systemic bone marker expression induced by grey and white mineral trioxide aggregate in normal and diabetic conditions

AIM

To investigate the relationship between diabetes mellitus and local/systemic effects of both grey and white mineral trioxide aggregate (MTA) Angelus on bone marker expression.

METHODOLOGY

Wistar rats were divided into two groups: healthy and diabetic (Alloxan induced), which were further divided into three subgroups (control, GMTA Angelus and WMTA Angelus). Polyethylene tubes filled with MTA materials or empty tubes were implanted in dorsal connective tissue. On days 7 and 30, blood samples were collected for calcium, phosphorus and ALP measurement. The animals were euthanized; implanted tubes were removed and processed for immunohistochemical analysis of osteocalcin (OCN) and osteopontin (OPN). Kruskal-Wallis followed by Dunn's multiple comparison test was performed for nonparametric data, and anova followed by Tukey's test for parametric data.

RESULTS

No difference in systemic serum calcium levels between both groups was observed. On day 7, serum phosphorus levels within the WMTA healthy group were higher than that of the diabetic group. On day 30, healthy rats exhibited lower phosphorus levels than diabetic ones. At both time points, the diabetic group was associated with more ALP activity than the healthy group. Immunohistochemical analyses of the healthy group revealed OCN- and OPN-positive cells in the presence of both MTA materials. However, under diabetic conditions, both OCN and OPN were absent.

CONCLUSION

Both MTA materials were associated with an increase in serum calcium, phosphorus and ALP, suggesting a potential systemic effect, along with triggered differentiation of OCN- and OPN-positive cells. Moreover, in diabetic conditions, an inhibitory effect on MTA-induced differentiation of OCN- and OPN-positive cells was detected.

Does Oxidative Stress Play a Role in Altered Characteristics of Diabetic Bone? A Systematic Review

Diabetes mellitus (DM) has been associated with increased bone fracture rates, impaired bone regeneration, delayed bone healing, and depressed osteogenesis. However, the plausible pathogenic mechanisms remain incompletely understood. The aim of the present systematic review was to investigate whether oxidative stress (OS) plays a role in altered characteristics of diabetic bone under in vivo conditions. An electronic search of the MEDLINE (via PubMed) and Embase databases was performed. In vivo animal studies involving DM and providing information regarding assessment of OS markers combined with analyses of bone histology/histomorphometry parameters were selected. A descriptive analysis of selected articles was performed. Ten studies were included in the present review. Both bone formation and bone resorption parameters were significantly decreased in the diabetic groups of animals compared to the healthy groups. This finding was consistent regardless of different animal/bone models employed or different evaluation periods. A statistically significant increase in systemic and/or local OS status was also emphasised in the diabetic groups in comparison to the healthy ones. Markers of OS were associated with histological and/or histomorphometric parameters, including decreased trabecular bone and osteoid volumes, suppressed bone formation, defective bone mineralisation, and reduced osteoclastic activity, in diabetic animals. Additionally, insulin and antioxidative treatment proved to be efficient in reversing the deleterious effects of high glucose and associated OS. The present findings support the hypotheses that OS in the diabetic condition contributes at least partially to defective bone features, and that antioxidative supplementation can be a valuable adjunctive strategy in treating diabetic bone disease, accelerating bone healing, and improving osteointegration.

Effects of glucose concentration on osteogenic differentiation of type II diabetes mellitus rat bone marrow-derived mesenchymal stromal cells on a nano-scale modified titanium

BACKGROUND AND OBJECTIVE

Diabetes mellitus (DM) is a common disease worldwide. Patients with DM have an increased risk of losing their teeth compared with other individuals. Dental implants are a standard of care for treating partial or full edentulism, and various implant surface treatments have recently been developed to increase dental implant stability. However, some studies have reported that DM reduces osseointegration and the success rate of dental implants. The purpose of this study was to determine the effects of high glucose levels for hard tissue formation on a nano-scale modified titanium surface.

MATERIAL AND METHODS

Titanium disks were heated at 600°C for 1 h after treatment with or without 10 m NaOH solution. All disks were incubated with type II DM rat bone marrow-derived mesenchymal stromal cells before exposure to one of four concentrations of glucose (5.5, 8.0, 12.0 or 24.0 mm). The effect of different glucose concentrations on bone marrow-derived mesenchymal stromal cell osteogenesis and inflammatory cytokines on the nano-scale modified titanium surface was evaluated.

RESULTS

Alkaline phosphatase activity decreased with increasing glucose concentration. In contrast, osteocalcin production and calcium deposition were significantly decreased at 8.0 mm glucose, but increased with glucose concentrations over 8.0 mm. Differences in calcium/phosphate ratio associated with the various glucose concentrations were similar to osteocalcin production and calcium deposition. Inflammatory cytokines were expressed at high glucose concentrations, but the nano-scale modified titanium surface inhibited the effect of high glucose concentrations.

CONCLUSION

High glucose concentration increased hard tissue formation, but the quality of the mineralized tissue decreased. Furthermore, the nano-scale modified titanium surface increased mineralized tissue formation and anti-inflammation, but the quality of hard tissue was dependent on glucose concentration.

Comparison of periodontal and peri-implant inflammatory parameters among patients with prediabetes, type 2 diabetes mellitus and non-diabetic controls

OBJECTIVE

The aim was to compare periodontal and periimplant inflammatory parameters (plaque index [PI], bleeding on probing [BOP], probing depth [PD] and marginal bone loss [MBL]) among patients with prediabetes, type-2 diabetes mellitus (T2DM) and non-diabetic controls.

MATERIALS AND METHODS

Forty-five patients with prediabetes (Group-1), 43 patients with T2DM (Group-2) and 42 controls (Group-3) were included. Demographic data was recorded using a questionnaire. Full mouth and periimplant clinical (PI, BOP and PD) were assessed and the radiographic MBL were measured on digital radiographs. In all groups, haemoglobin A1c (HbA1c) levels were also measured. p values less than .05 were considered statistically significant.

RESULTS

The mean HbA1c levels of participants in groups 1, 2 and 3 were 6.1%, 8.4% and 4.8%, respectively. The mean duration of prediabetes and T2DM among patients in groups 1 and 2 were 1.9 ± 0.3 and 3.1 ± 0.5 years, respectively. Periodontal and periimplant PI, BOP, PD and MBL were higher in groups 1 (p < .05) and 2 (p < .05) than group 3. There was no difference in these parameters in groups 1 and 2.

CONCLUSIONS

Periodontal and periimplant inflammatory parameters were worse among patients with prediabetes and T2DM compared with controls; however, these parameters were comparable among patients with prediabetes and T2DM.

Bone remodeling during orthodontic tooth movement in rats with type 2 diabetes

INTRODUCTION

Type 2 diabetes is known to affect bone metabolism. In this study, we aimed to determine the effects of type 2 diabetes on bone remodeling during orthodontic tooth movement.

METHODS

The 48 rats were divided into 4 groups: Wistar control group (n = 8), Goto-Kakizaki (GK) control group (n = 8), Wistar appliance group (n = 16), and GK appliance group (n = 16). The distances between the teeth were measured weekly. On day 42, maxillary alveolar bone specimens were obtained for histologic evaluation and determination of the gene expression levels of the receptor activator of nuclear factor ҡB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG).

RESULTS

No significant difference was observed in the levels of tooth movement between the 2 appliance groups. After orthodontic force application, the alveolar bone volume and osteoblast surface in the GK rats were diminished compared with those in the Wistar rats. The increase in the osteoclast surface relative to the control groups was 2.4-fold greater in the GK rats than in the Wistar rats. Significant upregulations of the RANK and OPG gene expression levels in the Wistar appliance group were observed. The RANKL/OPG ratio was increased in the GK appliance group compared with the Wistar appliance group.

CONCLUSIONS

Diminished bone formation and slightly increased bone resorption were observed during orthodontic tooth movement in the rats with type 2 diabetes.

Effect of targeted delivery of bone morphogenetic protein-2 on bone formation in type 1 diabetes

PURPOSE

Bone formation and healing are diminished in experimental type 1 diabetes. The present study investigated whether controlled local release of recombinant human bone morphogenetic protein 2 (rhBMP-2) stimulates bone defect healing in diabetes as a consequence of its anabolic effects on bone.

MATERIALS AND METHODS

Bilateral experimental circular bone defects were created in the temporal bones of 64 BALB/cByJ mice. Defects were treated with acellular collagen sponge plus 0.4 or 1.8 μg of rhBMP-2 per defect, and untreated defects served as controls. The healing of the defects over a 14-day period in diabetic and nondiabetic mice was analyzed histomorphometrically.

RESULTS

Diabetes inhibited bone formation in both untreated and BMP-treated bone defects. Controlled local release of rhBMP-2 significantly stimulated bone formation in diabetic animals, bringing it nearly to normal levels, and enhanced bone regeneration in normal animals.

CONCLUSION

Recombinant human BMP-2 may be beneficial in treating deficient intramembranous bone formation in diabetes.

Ex Vivo Modeling of Multidomain Peptide Hydrogels with Intact Dental Pulp

Preservation of a vital dental pulp is a central goal of restorative dentistry. Currently, there is significant interest in the development of tissue engineering scaffolds that can serve as biocompatible and bioactive pulp-capping materials, driving dentin bridge formation without causing cytotoxic effects. Our earlier in vitro studies described the biocompatibility of multidomain peptide (MDP) hydrogel scaffolds with dental pulp-derived cells but were limited in their ability to model contact with intact 3-dimensional pulp tissues. Here, we utilize an established ex vivo mandible organ culture model to model these complex interactions. MDP hydrogel scaffolds were injected either at the interface of the odontoblasts and the dentin or into the pulp core of mandible slices and subsequently cultured for up to 10 d. Histology reveals minimal disruption of tissue architecture adjacent to MDP scaffolds injected into the pulp core or odontoblast space. Additionally, the odontoblast layer is structurally preserved in apposition to the MDP scaffold, despite being separated from the dentin. Alizarin red staining suggests mineralization at the periphery of MDP scaffolds injected into the odontoblast space. Immunohistochemistry reveals deposition of dentin sialophosphoprotein by odontoblasts into the adjacent MDP hydrogel, indicating continued functionality. In contrast, no mineralization or dentin sialophosphoprotein deposition is evident around MDP scaffolds injected into the pulp core. Collagen III expression is seen in apposition to gels at all experimental time points. Matrix metalloproteinase 2 expression is observed associated with centrally injected MDP scaffolds at early time points, indicating proteolytic digestion of scaffolds. Thus, MDP scaffolds delivered centrally and peripherally within whole dental pulp tissue are shown to be biocompatible, preserving local tissue architecture. Additionally, odontoblast function and pulp vitality are sustained when MDP scaffolds are intercalated between dentin and the odontoblast region, a finding that has significant implications when considering these materials as pulp-capping agents.

A 3D ex vivo mandible slice system for longitudinal culturing of transplanted dental pulp progenitor cells

Harnessing mesenchymal stem cells for tissue repair underpins regenerative medicine. However, how the 3D tissue matrix maintains such cells in a quiescent state whilst at the same time primed to respond to tissue damage remains relatively unknown. Developing more physiologically relevant 3D models would allow us to better understand the matrix drivers and influence on cell‐lineage differentiation in situ. In this study, we have developed an ex vivo organotypic rat mandible slice model; a technically defined platform for the culture and characterization of dental pulp progenitor cells expressing GFP driven by the β‐actin promoter (cGFP DPPCs). Using confocal microscopy we have characterized how the native environment influences the progenitor cells transplanted into the dental pulp. Injected cGFP‐DPPCs were highly viable and furthermore differentially proliferated in unique regions of the mandible slice; in the dentine region, cGFP‐DPPCs showed a columnar morphology indicative of expansion and lineage differentiation. Hence, we demonstrated the systematic capacity for establishing a dental pulp cell‐micro‐community, phenotypically modified in the tooth (the “biology”); and at the same time addressed technical challenges enabling the mandible slice to be accessible on platforms for high‐content imaging (the biology in a “multiplex” format). © 2015 The Authors. Published by Wiley Periodicals, Inc.

Influence of Immunogenicity of Allogeneic Bone Marrow Mesenchymal Stem Cells on Bone Tissue Engineering

Allogeneic bone marrow mesenchymal stem cell (allo-BMSC)-based tissue-engineered bone (TEB) has great potential for bone defect repair. However, the immunogenicities and biological roles of allo-BMSCs are still controversial. In this study, we established an animal model of critical-sized mandibular defect in beagle dogs and compared the repairing effects of allo-BMSC-based TEB with autogenic BMSC (auto-BMSC)-based TEB without the administration of immunosuppressants. During the first 2 weeks postimplantation, a transient immune response in the allo-BMSC group was detected with an increase in proinflammation cytokines TNF-α, IFN-γ, and IL-2, a declination of anti-inflammation cytokine IL-10, and an increase in percentages of CD4(+) and CD8(+) T-cell subsets in peripheral blood. Nevertheless, there was no significant difference in bone union achievement, bone mineral density, and biomechanical properties between the two groups at 12 and 24 weeks postimplantation. Further subcutaneous implantation of allo-BMSCs/scaffold also exhibited the similar transient immune responses in the first 2 weeks postimplantation but followed by a decreased bone formation at 4 and 8 weeks postimplantation. These findings indicate that allo-BMSCs can induce a transient immunoreaction, which may temporally delay the osteogenesis of allo-BMSC/scaffold complex in early stage of in vivo implantation, whereas the long-term engineered bone formation was not affected.

Key systemic and environmental risk factors for implant failure

Dental implants are an important treatment option for patients interested in replacing lost or missing teeth. Although a robust body of literature has reviewed risk factors for tooth loss, the evidence for risk factors associated with dental implants is less well defined. This article focuses on key systemic risk factors relating to dental implant failure, as well as on perimucositis and peri-implantitis.

Evaluation of skeletal tissue repair, part 1: assessment of novel growth-factor-releasing hydrogels in an ex vivo chick femur defect model

Current clinical treatments for skeletal conditions resulting in large-scale bone loss include autograft or allograft, both of which have limited effectiveness. In seeking to address bone regeneration, several tissue engineering strategies have come to the fore, including the development of growth factor releasing technologies and appropriate animal models to evaluate repair. Ex vivo models represent a promising alternative to simple in vitro systems or complex, ethically challenging in vivo models. We have developed an ex vivo culture system of whole embryonic chick femora, adapted in this study as a critical size defect model to investigate the effects of novel bone extracellular matrix (bECM) hydrogel scaffolds containing spatio-temporal growth factor-releasing microparticles and skeletal stem cells on bone regeneration, to develop a viable alternative treatment for skeletal degeneration. Alginate/bECM hydrogels combined with poly (d,l-lactic-co-glycolic acid) (PDLLGA)/triblock copolymer (10-30% PDLLGA-PEG-PDLLGA) microparticles releasing VEGF, TGF-β3 or BMP-2 were placed, with human adult Stro-1+ bone marrow stromal cells, into 2mm central segmental defects in embryonic chick femurs. Alginate/bECM hydrogels loaded with HSA/VEGF or HSA/TGF-β3 demonstrated a cartilage-like phenotype, with minimal collagen I deposition, comparable to HSA-only control hydrogels. The addition of BMP-2 releasing microparticles resulted in enhanced structured bone matrix formation, evidenced by increased Sirius red-stained matrix and collagen expression within hydrogels. This study demonstrates delivery of bioactive growth factors from a novel alginate/bECM hydrogel to augment skeletal tissue formation and the use of an organotypic chick femur defect culture system as a high-throughput test model for scaffold/cell/growth factor therapies for regenerative medicine.

Assessment of Maxillary and Mandibular Bone Density in Controlled Type II Diabetes: A Computed Tomography Study

This study was undertaken to compare the bone density in nondiabetic and controlled type II diabetes patients using spiral computed tomography. A group of 40 edentulous men, comprising of 20 nondiabetics and 20 controlled type II diabetics between the ages of 50-65 years, were enrolled in the study. Glycemic control of the diabetic patients was assessed by glycosylated hemoglobin level. The controlled diabetic group had an HbA1c level between 6.1-8%. A radiographic stent was prepared by using chemically cured resin. Bone densities at trabecular, buccal, and lingual cortical regions of maxillary and mandibular edentulous arches were measured by a tomography machine. Mean bone density measurements were recorded in Hounsfield units. The data thus obtained from 10 sites of maxillary and mandibular arches were tabulated and analyzed using SPSS statistical software. This study showed no significant changes in bone density between the controlled diabetic and nondiabetic subjects. Within the limitation of this study, it can be concluded that bone density does not seem to be affected in controlled type II diabetics.

Effect of reactive oxygen species overproduction on osteogenesis of porous titanium implant in the present of diabetes mellitus

Clinical evidence indicates diabetes as a majorrisk factor for titaniumimplant treatment with high failure rates and poor osteointegration, but the underlying mechanism involved remains elusive.We hypothesize that reactive oxygen species (ROS) overproduction may contribute to the impaired osteogenesis of porous titanium implants (pTi) under diabetic conditions. To test this hypothesis, we culturedprimary rabbit osteoblasts onto pTi and studied the cellular performance when subjected to normal serum (NS), diabetic serum (DS), DS + NAC (a potent ROS inhibitor) and NS + H(2)O(2)(an oxidant).In-vivo performance of pTi was investigated by transplanting them intofemoral condyledefects of diabetic rabbits, which received vehicle or NAC treatment respectively.Results showed that diabetic conditions induced significant cellular apoptosis, depressedosteoblast function evidenced by impairedcell attachment and morphology, decreased cell proliferation anddifferentiation, andcompromised in-vivo osteogenesis ofpTi, while cellular ROSgeneration was increased derived from mitochondrial dysfunction. Scavenging ROS with NAC markedly attenuated cell apoptosis and osteoblast dysfunction, and improved bone ingrowth within pTi. Furthermore, treatment withH(2)O(2) exerted similar adverse effect on cellular behavior as diabetes. This study furthers our knowledge on the potential role of ROS overproduction in the diabetes-induced impaired osteogenesis of titanium implants, and indicates anti-oxidative treatment as a promising strategy to promote the treatment efficacy of pTi in diabetic patients.