Effect of high glucose levels and lipopolysaccharides-induced inflammation on osteoblast mineralization over sandblasted/acid-etched titanium surface

Limosilactobacillus reuteri supernatant attenuates inflammatory responses of human gingival fibroblasts to LPS but not to elevated glucose levels

AIM

We investigated the in vitro effect of Limosilactobacillus reuteri DSM 17938 supernatant on the inflammatory response of human gingival fibroblasts (HGF) challenged by lipopolysaccharide (LPS) or elevated glucose levels.

METHODS

HGF were exposed to LPS (1 μg/mL), glucose (5, 12 mM or 25 mM), and dilutions of supernatant prepared from L. reuteri DSM 17938 (0.5 × 107, 1.0 × 107, 2.5 × 107, and 5.0 × 107 CFU/mL). After 24 h cell viability and levels of cytokines (IL-1β, IL-6 and IL-8) and TLR-2 were determined.

RESULTS

None of the tested L. reuteri (DSM 17938) supernatant concentrations reduced the viability of HGF. Supernatant concentrations (2.5 × 107 and 5 × 107 CFU/mL) significantly (p < .05) decreased the production of IL-1β, IL-6, IL-8, and TLR-2 in the presence of LPS. In contrast, inflammatory markers were not reduced by L. reuteri supernatant in the presence of glucose. Glucose concentrations of 12 mM and 24 mM still lead to an elevated production of the investigated biochemical mediators.

CONCLUSION

While L. reuteri (DSM 17938) supernatant attenuates the inflammatory response of HGF to LPS in a dose-dependent manner, elevated glucose levels suppress this action. These in vitro results support the overall anti-inflammatory efficacy of L. reuteri supplementation in plaque-associated periodontal inflammations.

NP-12 peptide functionalized nanoparticles counteract the effect of bacterial lipopolysaccharide on cultured osteoblasts

OBJECTIVE

To evaluate whether nanoparticles (NPs) functionalized with Tideglusib (TDg, NP-12), and deposited on titanium surfaces, would counteract the effect of bacterial lipopolysaccharide (LPS) on osteoblasts.

METHODS

Experimental groups were: (a) Titanium discs (TiD), (b) TiD covered with undoped NPs (Un-NPs) and (c) TiD covered with TDg-doped NPs (TDg-NPs). Human primary osteoblasts were cultured onto these discs, in the presence or absence of bacterial LPS. Cell proliferation was assessed by MTT-assay and differentiation by measuring the alkaline phosphatase activity. Mineral nodule formation was assessed by the alizarin red test. Real-time quantitative polymerase chain reaction was used to study the expression of Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF-βR2, and TGF-βR3 genes. Osteoblasts morphology was studied by Scanning Electron Microscopy. One-way ANOVA or Kruskal-Wallis and Bonferroni multiple comparisons tests were carried out (p < 0.05).

RESULTS

TDg-NPs enhanced osteoblasts proliferation. Similarly, this group increased ALP production and mineral nodules formation. TDg-NPs on titanium discs resulted in overexpression of the proliferative genes, OSC and OSX, regardless of LPS activity. In the absence of LPS, TDg-NPs up-regulated Runx2, COL-I, ALP, BMP2 and BMP7 genes. OPG/RANKL gene ratios were increased about 2500 and 4,000-fold by TDg-NPs, when LPS was added or not, respectively. In contact with the TDg-NPs osteoblasts demonstrated an elongated spindle-shaped morphology with extracellular matrix production.

SIGNIFICANCE

TDg-NPs on titanium discs counteracted the detrimental effect of LPS by preventing the decrease on osteoblasts proliferation and mineralization, and produced an overexpression of proliferative and bone-promoting genes on human primary osteoblasts.

Calcium phytate reverses high glucose-inhibited osteogenesis of BMSCs via the MAPK/JNK pathway

OBJECTIVES

Diabetes mellitus (DM) induces oxidative tissue impairment and suppresses bone formation. Some studies have shown that phytic acid has antioxidant and anti-diabetic properties. This study aimed to investigate the potential of calcium phytate (Ca-phytate) to reverse inhibited osteogenesis of human bone marrow mesenchymal stem cells (hBMSCs) in a high glucose (HG) environment and to determine the underlying mechanism.

MATERIALS AND METHODS

hBMSCs were exposed to HG and palmitic acid to simulate DM in vitro. Osteogenic differentiation was measured using alkaline phosphatase staining and activity assay, alizarin red S staining, qRT-PCR, Western blot and immunofluorescence staining. A critical-size cranial defect model of type 2 diabetes mellitus (T2DM) rats was established to evaluate bone regeneration. A specific pathway inhibitor was used to explore whether the MAPK/JNK pathway was involved.

RESULTS

Treatment with 34 μM Ca-phytate had the highest effect on osteogenic differentiation in HG. Ca-phytate improved cranial bone defect healing in T2DM rats. The long-term HG environment inhibited the activation of the MAPK/JNK signalling pathway, which was restored by Ca-phytate. Blocking the JNK pathway reduced the Ca-phytate-mediated osteogenic differentiation of hBMSCs.

CONCLUSION

Ca-phytate induced bone regeneration in vivo and reversed HG-inhibited osteogenesis of hBMSCs in vitro via the MAPK/JNK signalling pathway.

Osteogenesis Performance of Boronized Ti6Al4V/HA Composites Prepared by Microwave Sintering: In Vitro and In Vivo Studies

The boronized Ti6Al4V/HA composite is deemed to be an important biomaterial because of its potential remarkable mechanical and biological properties. This paper reports the osteogenesis performance of the boronized Ti6Al4V/HA composite, which was prepared by microwave sintering of powders of Ti6Al4V, hydroxyapatite (HA), and TiB₂ in high-purity Ar gas at 1050 °C for 30 min, as dental implant based on both cell experiments in vitro and animal experiments in vivo. The comparison between the boronized Ti6Al4V/HA composite and Ti, Ti6Al4V, and boronized Ti6Al4V in the terms of adhesion, proliferation, alkaline phosphate (ALP) activity, and mineralization of MG-63 cells on their surfaces confirmed that the composite exhibited the best inductive osteogenesis potential. It exerted a more significant effect on promoting the early osteogenic differentiation of osteoblasts and exhibited the maximum optical density (OD) value in the MTT assay and the highest levels of ALP activity and mineralization ability, primarily ascribed to its bioactive HA component, porous structure, and relatively rough micro-morphology. The in vivo study in rabbits based on the micro-computed tomography (micro-CT) analysis, histological and histomorphometric evaluation, and biomechanical testing further confirmed that the boronized Ti6Al4V/HA composite had the highest new bone formation potential and the best osseointegration property after implantation for up to 12 weeks, mainly revealed by the measured values of bone volume fraction, bone implant contact, and maximum push-out force which, for example, reached 48.64%, 61%, and 150.3 ± 6.07 N at the 12th week. Owing to these inspiring features, it can serve as a highly promising dental implant.

Silk Fibroin/Hydroxyapatite Coating Improved Osseointegration of Porous Titanium Implants under Diabetic Conditions via Activation of the PI3K/Akt Signaling Pathway

The application of three-dimensional printed porous titanium implants (TIs) is compromised in patients suffering from diabetes mellitus (DM), which disturbs the normal process of implant osseointegration, resulting in fixation failure. It was possibly because of reactive oxygen species (ROS) overproduction at the bone-implant interface. A silk fibroin-based hydroxyapatite (SF/HA) hybrid material emerged as a novel biological material for accelerating new bone formation. We proposed that the SF/HA hybrid coated titanium implant (SHT) could mitigate DM-mediated impaired osseointegration, which had never been reported previously. To test this assumption and further elucidate the mechanisms, primary rabbit osteoblasts were seeded on TIs or SHTs and cultured with normal serum, diabetic serum (DS), DS + N-acetyl-L-cysteine (NAC) (a potent ROS inhibitor), and DS + LY294002 (a specific PI3K/Akt inhibitor) for osteoblast behavior examinations. An animal study was performed on diabetic rabbits implanted with the two kinds of implants for osseointegration tests. DM-mediated ROS overproduction caused osteoblastic biological dysfunctions and apoptotic injury, associated with suppression of PI3K/Akt signaling in osteoblasts cultured on a TI substrate. Of note, the SHT substrate significantly suppressed ROS overproduction under diabetic conditions, improved osteoblast functional recovery including ameliorative osteoblast adhesion and morphology, improved cellular proliferation and differentiation, and abrogated apoptosis, which exhibited the same effect as NAC administration on the TI. The in vitro results were further corroborated in vivo by enhanced osteogenesis and osseointegration of SHTs in diabetic rabbits. Moreover, the aforesaid promotive effects afforded by the SF/HA coating were totally abolished with administration of LY294002 for blocking PI3K/Akt signaling. The above results collectively demonstrated that the SF/HA hybrid coating significantly ameliorated DM-mediated impaired osseointegration of the TI via reactivation of the ROS-mediated PI3K/Akt signaling pathway. The hybrid coating elicited a novel surface biofunctionalization strategy to attain favorable clinical performance of TI in diabetics.

Combination of enamel matrix derivative and hyaluronic acid inhibits lipopolysaccharide-induced inflammatory response on human epithelial and bone cells

Objectives

The aim of this study was to evaluate the in vitro effect of enamel matrix derivative (EMD) and hyaluronic acid (HA) and their synergistic combination on lipopolysaccharides (LPS)-induced inflammation in human keratinocytes and osteoblasts.

Material and methods

Cells were challenged with LPS (1 μg/ml) and cultured in the following treatment groups with EMD (30 mg/ml) and HA (30 mg/ml): LPS, EMD, HA, EMD + HA, EMD + LPS, HA + LPS, and EMD + HA + LPS. Cell viability, inflammatory cytokine expression, and cell migration were determined using colorimetric assay, quantitative real-time polymerase chain reaction (qPCR), and scratch wound healing assay, respectively.

Results

Cell viability was decreased when exposed to LPS compared to the controls. Overall, LPS treatment expressed upregulation on inflammatory cytokine tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6). EMD and HA reduced up to 3.0-fold the cytokine expression caused by LPS (p < 0.05). EMD and HA statistically induced higher migration in osteoblasts and keratinocytes, respectively. Migration was impaired by LPS, whereas it significantly increased after addition of EMD and HA.

Conclusions

EMD and HA are advantageous biomaterials that individually generate strong directional migratory keratinocyte and osteoblast response. Their combination also enhances cell viability, and anti-inflammatory and migratory abilities to promote healing specially under LPS inflammatory stimulus. Future in vivo and animal research is necessary to further characterize the effect of EMD and HA on periodontal regeneration.

Clinical relevance

The use of EMD in conjunction with HA resulted in a reduction of inflammation and improvement of tissue healing at wound sites. Both biomaterials combined may potentially improve the effectiveness of bone regeneration in periodontal bone defects, pointing to the potential clinical relevance of both materials in regenerative periodontal surgery.

Histological and Nanomechanical Properties of a New Nanometric Hydroxiapatite Implant Surface. An In Vivo Study in Diabetic Rats

Implant therapy is a predictable treatment to replace missing teeth. However, the osseointegration process may be negatively influenced by systemic conditions, such as diabetes mellitus (DM). Microtopography and implant surface developments are strategies associated to better bone repair. This study aimed to evaluate, in healthy and diabetic rats, histomorphometric (bone to implant contact = %BIC; and bone area fraction occupancy = %BAFO) and nanomechanical (elastic modulus = EM; and hardness = H) bone parameters, in response to a nanometric hydroxyapatite implant surface. Mini implants (machined = MAC; double acid etched = DAE, and with addition of nano-hydroxyapatite = NANO) were installed in tibias of healthy and diabetic rats. The animals were euthanized at 7 and 30 days. NANO surface presented higher %BIC and %BAFO when compared to MAC and DAE (data evaluated as a function of implant surface). NANO surface presented higher %BIC and %BAFO, with statistically significant differences (data as a function of time and implant surface). NANO surface depicted higher EM and H values, when compared to machined and DAE surfaces (data as a function of time and implant surface). Nano-hydroxyapatite coated implants presented promising biomechanical results and could be an important tool to compensate impaired bone healing reported in diabetics.

Influence of nano-hydroxyapatite coating implants on gene expression of osteogenic markers and micro-CT parameters. An in vivo study in diabetic rats

This study evaluated the response of a nano-hydroxyapatite coating implant through gene expression analysis (runt-related transcription factor 2 (Runx2), alkaline phosphatase (Alp), osteopontin (Opn), osteocalcin (Oc), receptor activator of nuclear factor-kappa B (Rank), receptor activator of nuclear factor-kappa B ligand (Rank-L), and osteoprotegerin (Opg)). Three-dimensional evaluation (percent bone volume (BV/TV); percent intersection surface (BIC); bone surface/volume ratio (BS/BV); and total porosity (To.Po)) were also analyzed. Mini implants were surgically placed in tibias of both healthy and diabetic rats. The animals were euthanized at 7 and 30 days. Evaluating all factors the relative expression of Rank showed that NANO surface presented the best results at 7 days (diabetic rats). Furthermore the levels of Runx2, Alp, Oc, and Opn suggest an increase in osteoblasts proliferation, especially in early stages of osseointegration. %BIC in healthy and diabetic (7 days) depicted statistically significant differences for NANO group. BV/TV, BS/BV and To.Po demonstrated higher values for NANO group in all evaluated time point and irrespective of systemic condition, but BS/BV 30 days (healthy rat) and 7 and 30 days (diabetic rat). Microtomographic and gene expression analyses have shown the benefits of nano-hydroxyapatite coated implants in promoting new bone formation in diabetic rats.