Boric Acid Inhibits RANKL-Stimulated Osteoclastogenesis In Vitro and Attenuates LPS-Induced Bone Loss In Vivo

Histopathological and radiological evaluation of the efficacy of hydroxyapatite-boric acid and hydroxyapatite-magnesium coated Kirschner wires on fracture healing in femoral diaphyseal fractures: an experimental study

BACKGROUND

Biomaterials used in fracture healing hold a significant place in orthopedics. This study aimed to develop biomaterials coated with hydroxyapatite (HA), boric acid (BA), and magnesium (Mg) and investigate their effects on fracture healing.

METHODS

Sixty female Wistar Albino rats were included in the study. The subjects were randomized into five groups. Cytotoxicity tests were performed on HA, BA, and Mg, and cell viability rates were calculated. Coatings were applied to Kirschner (K) wires at determined ratios. Group I was the control group with a steel K wire, Group II used HA-coated K wires, Group III used HA + BA-coated K wires, Group IV used HA + BA + Mg-coated K wires, and Group V used HA + Mg-coated K wires. A fracture was induced in the right femur of the subjects, followed by fixation with intramedullary K wires. The subjects were randomly divided into equal numbers and sacrificed at 6 and 12 weeks. Radiological and histopathological evaluations were performed.

RESULTS

In direct cytotoxicity tests, the highest viability rate was observed in Group IV, while in indirect cytotoxicity tests, it was highest in Group II. In radiological evaluation at the 6th week, the highest scores were in Groups IV and V, while the lowest was in Group III. At the 12th week, the highest scores were in Groups II and V, while the lowest was in Group I. No significant differences were found between the groups (p = 0.837, p = 0.0479). In histopathological evaluation, a significant difference was observed between the groups (p < 0.001), with the highest scores in Group V. A correlation was found between the radiological and histopathological scores (p < 0.001, r = 0.438).

CONCLUSION

It was found that HA + Mg significantly improved histological outcomes in fracture healing. Good histological results can be achieved with the use of Mg-containing implants in both early and late-stage fracture healing. Coating the biomaterials used in fracture fixation with Mg may lead to positive outcomes in fracture healing.

Surface Pre-Reacted Glass-Ionomer Eluate Suppresses Osteoclastogenesis through Downregulation of the MAPK Signaling Pathway

Surface pre-reacted glass-ionomer (S-PRG) is a new bioactive filler utilized for the restoration of decayed teeth by its ability to release six bioactive ions that prevent the adhesion of dental plaque to the tooth surface. Since ionic liquids are reported to facilitate transepithelial penetration, we reasoned that S-PRG applied to root caries could impact the osteoclasts (OCs) in the proximal alveolar bone. Therefore, this study aimed to investigate the effect of S-PRG eluate solution on RANKL-induced OC-genesis and mineral dissolution in vitro. Using RAW264.7 cells as OC precursor cells (OPCs), TRAP staining and pit formation assays were conducted to monitor OC-genesis and mineral dissolution, respectively, while OC-genesis-associated gene expression was measured using quantitative real-time PCR (qPCR). Expression of NFATc1, a master regulator of OC differentiation, and the phosphorylation of MAPK signaling molecules were measured using Western blotting. S-PRG eluate dilutions at 1/200 and 1/400 showed no cytotoxicity to RAW264.7 cells but did significantly suppress both OC-genesis and mineral dissolution. The same concentrations of S-PRG eluate downregulated the RANKL-mediated induction of OCSTAMP and CATK mRNAs, as well as the expression of NFATc1 protein and the phosphorylation of ERK, JNK, and p38. These results demonstrate that S-PRG eluate can downregulate RANKL-induced OC-genesis and mineral dissolution, suggesting that its application to root caries might prevent alveolar bone resorption.

Osteogenic Differentiation Capacity of Dental Pulp Stem Cells on 3D Printed Polyurethane/Boric Acid Scaffold

Additive manufacturing is growing in the area of dentistry and orthopedics due to the potential for the fabrication of individual implants. In this study, fused deposition modeling which is the most popular method was used to produce 3D scaffolds having a grid pattern from the polyurethane (PU) filament. Then, this scaffold was coated with boric acid (BA) with the thermionic vacuum arc technique. The microstructure analysis showed the macro-pores having a dimension of ~ 0.16 mm2. The BA coating increased the roughness in adverse decreased the wettability. The presence of BA on the scaffold before and after cell culture was confirmed by FESEM-EDS and ATR-FTIR. The Cell proliferation and osteogenic differentiation capacity of dental pulp stem cells (DPSCs) on uncoated and coated printed 3D PU scaffolds were also investigated. On the third day, cell viability was found to be higher (1.3-fold) in the groups containing BA. However, on the seventh day, the increase in cell proliferation in the PU+BA group was found to be less than in the other groups. According to Ca deposition analysis and Alizarin Red staining, PU+BA increased the calcium accumulation in the cells in both osteogenic induced and non-induced conditions at day 14. According to gene expression analysis, the Runx2 expression was not detected in PU+BA groups with and without differentiation medium (p ≤0.05). The expression of OCN was persistently increased up to 21-fold and 48-fold in cells on PU and PU+BA in osteogenic differentiation medium group after 14 days compared to control group (p ≤0.05). DSPP expression was observed only in PU+BA in osteogenic differentiation medium group. In line with the results that we have obtained, our 3D printed scaffolds have properties to trigger the differentiation of DPSCs cells in terms of osteogenicity.

ER Stress, the Unfolded Protein Response and Osteoclastogenesis: A Review

Endoplasmic reticulum (ER) stress and its adaptive mechanism, the unfolded protein response (UPR), are triggered by the accumulation of unfolded and misfolded proteins. During osteoclastogenesis, a large number of active proteins are synthesized. When an imbalance in the protein folding process occurs, it causes osteoclasts to trigger the UPR. This close association has led to the role of the UPR in osteoclastogenesis being increasingly explored. In recent years, several studies have reported the role of ER stress and UPR in osteoclastogenesis and bone resorption. Here, we reviewed the relevant literature and discussed the UPR signaling cascade response, osteoclastogenesis-related signaling pathways, and the role of UPR in osteoclastogenesis and bone resorption in detail. It was found that the UPR signal (PERK, CHOP, and IRE1-XBP1) promoted the expression of the receptor activator of the nuclear factor-kappa B ligand (RANKL) in osteoblasts and indirectly enhanced osteoclastogenesis. IRE1 promoted osteoclastogenesis via promoting NF-κB, MAPK signaling, or the release of pro-inflammatory factors (IL-6, IL-1β, and TNFα). CREBH promoted osteoclast differentiation by promoting NFATc1 expression. The PERK signaling pathway also promoted osteoclastogenesis through NF-κB and MAPK signaling pathways, autophagy, and RANKL secretion from osteoblasts. However, salubrinal (an inhibitor of eIF2α dephosphorylation that upregulated p-eIF2α expression) directly inhibited osteoclastogenesis by suppressing NFATc1 expression and indirectly promoted osteoclastogenesis by promoting RANKL secretion from osteoblasts. Therefore, the specific effects and mechanisms of p-PERK and its downstream signaling on osteoclastogenesis still need further experiments to confirm. In addition, the exact role of ATF6 and BiP in osteoclastogenesis also required further exploration. In conclusion, our detailed and systematic review provides some references for the next step to fully elucidate the relationship between UPR and osteoclastogenesis, intending to provide new insights for the treatment of diseases caused by osteoclast over-differentiation, such as osteoporosis.

Investigating effects of locally applied boric acid on fracture healing with and without low-level laser therapy

This study aimed to investigate the effects on fracture healing of locally applied boric acid (BA) with and without low-level laser therapy (LLLT). A unicortical femoral defect was surgically created on the anterolateral surface of proximal femur of each subject. The subjects, totaling 56 Wistar albino rats, were randomly allocated into four groups (n = 14 each): control, LLLT (λ = 905 μm, 10,000 Hz, 25 mW, and peak power 25 W), BA (40 mg/kg), and BA + LLLT groups. On the 30th day, the highest radiological score was recorded for the BA + LLLT group (3.63 [2-4]), followed by the BA (3.38 [2.75-3.75]), control (3 [2-3.25]), and LLLT (2.5 [1.25-3]) groups. On days 15 and 30 post-surgery, malondialdehyde levels were significantly lower among the BA + LLLT group compared to the control group (p < 0.001). On day 30, superoxide dismutase, catalase, and alkaline phosphatase levels were highest in the BA + LLLT group compared to the control group (p < 0.001). When the histopathological, immunofluorescence, and immunohistochemical findings on the 15th and 30th days were compared with the control group, a statistically significant difference was found for the BA and BA + LLLT groups (p ˂ 0.05). This study suggests that locally applied BA with LLLT may accelerate fracture healing.