Influence of bisphosphonates on the adherence and metabolism of epithelial cells and gingival fibroblasts to titanium surfaces

Interleukin-17 plays a role in dental pulp inflammation mediated by zoledronic acid: a mechanism unrelated to the Th17 immune response?

OBJECTIVE

To evaluate the influence of RORγT inhibition by digoxin on inflammatory changes related to interleukin-17 (IL-17) in the pulp of rats treated with zoledronate (ZOL).

METHODOLOGY

Forty male Wistar rats were divided into a negative control group (NCG) treated with saline solution, a positive control group (PCG) treated with ZOL (0.20 mg/kg), and three groups treated with ZOL and co-treated with digoxin 1, 2, or 4 mg/kg (DG1, 2, and 4). After four intravenous administrations of ZOL or saline solution in a 70-day protocol, the right molars were evaluated by histomorphometry (number of blood vessels, blood vessels/µm2, cells/µm2, total blood vessel area, and average blood vessel area) and immunohistochemistry (IL-17, TNF-α, IL-6, and TGF-β). The Kruskal-Wallis/Dunn test was used for statistical analysis.

RESULTS

PCG showed an increase in total blood vessel area (p=0.008) and average blood vessel area (p=0.014), and digoxin treatment reversed these changes. DG4 showed a reduction in blood vessels/µm2 (p<0.001). In PCG odontoblasts, there was an increase in IL-17 (p=0.002) and TNF-α (p=0.002) immunostaining, and in DG4, these changes were reversed. Odontoblasts in the digoxin-treated groups also showed an increase in IL-6 immunostaining (p<0.001) and a reduction in TGF-β immunostaining (p=0.002), and all ZOL-treated groups showed an increase in IL-17 (p=0.011) and TNF-α (p=0.017) in non-odontoblasts cells.

CONCLUSION

ZOL induces TNF-α- and IL-17-dependent vasodilation and ectasia, and the classical Th17 response activation pathway does not seem to participate in this process.

Osteonecrosis of the Jaw

Osteonecrosis of the jaw is a condition in which bone cells die due to various causes. It is classified as drug-induced jaw osteonecrosis, osteoradionecrosis, traumatic, non-traumatic, and spontaneous osteonecrosis. Antiresorptive or antiangiogenic drugs cause drug-induced osteonecrosis. The combination of medications, microbial contamination, and local trauma induces this condition. Osteoradionecrosis is a severe radiation therapy side effect that can affect people with head and neck cancer. It is described as an exposed bone area that does not heal for longer than three months after the end of radiation treatment with the absence of any indications of an original tumor, recurrence, or metastasis. Trauma (tooth extraction), tumor site, radiation dose that the patient receives, the area of the bone which is irradiated, oral hygiene, and other factors are risk factors for the development of osteonecrosis. Less frequently, osteonecrosis can also be induced by non-traumatic and traumatic causes. Non-traumatic osteonecrosis is brought on by infections, acquired and congenital disorders, as well as the impact of chemicals. Traumatic osteonecrosis is brought on by thermal, mechanical, or chemical damage. The treatment of osteonecrosis can be conservative, which aims to be beneficial for the patient's quality of life, and surgical, which involves debridement of the necrotic bone.

Titanium alkalinization improves response of osteoblasts to zoledronic acid

This investigation is aimed to determine the effect of the modification of titanium surface with NaOH on the metabolism of osteoblasts treated with zoledronic acid (ZA). Machined and NaOH-treated titanium disks were used. Surfaces were characterized by scanning electron microscopy, confocal microscopy, and x-ray photoelectron spectroscopy (XPS) analysis. Human osteoblasts were seeded onto the disks. After 24 h, cells were treated with ZA at 5 μM for 7 days. At this point, cell viability, collagen synthesis, total protein production, alkaline phosphatase activity, and mineral nodule deposition were assessed. The results of surface roughness were descriptively and statistically analyzed (t-Student), while the XPS results were qualitatively described. Cell metabolism data were analyzed by the analysis of variance two-way and Tukey tests at a 5% significance level. The results demonstrated that NaOH-treatment increased surface roughness (p < .05) and confirmed the presence of sodium titanate and a pH switch on the NaOH-treated disks. This modification also resulted in higher cell viability, collagen synthesis, total protein production, and alkaline phosphatase by osteoblasts when compared to cells seeded onto machined disks (p < 0.05). In the presence of ZA, all cellular metabolism and differentiation parameters were significantly reduced for cells seeded on both surfaces (p < 0.05); however, the cells seeded onto modified surfaces showed higher values for these parameters, except for mineral nodule deposition (p < 0.05). NaOH modification improved cell adhesion and metabolism of osteogenic cells even in the presence of ZA. The surface modification of titanium with NaOH solution may be an interesting strategy to improve metabolism and differentiation of osteoblasts and accelerate osseointegration process, mainly for tissues exposed to ZA.

A Review Into the Effects of Pamidronic Acid and Zoledronic Acid on the Oral Mucosa in Medication-Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a growing problem without an effective treatment, presenting as necrotic bone sections exposed via lesions in the overlying soft tissue. There is currently a lack of clarity on how the factors involved in MRONJ development and progression contribute to disease prognosis and outcomes. Bisphosphonates (BPs), the most common cause of MRONJ, affect bone remodeling, angiogenesis, infection, inflammation and soft tissue toxicity, all of which contribute to MRONJ development. This article reviews the cellular mechanisms through which BPs contribute to MRONJ pathology, with a focus on the effects on cells of the oral mucosa. BPs have been shown to reduce cell viability, reduce proliferation, and increase apoptosis in oral keratinocytes and fibroblasts. BPs have also been demonstrated to reduce epithelial thickness and prevent epithelial formation in three-dimensional tissue engineered models of the oral mucosa. This combination of factors demonstrates how BPs lead to the reduced wound healing seen in MRONJ and begins to uncover the mechanisms through which these effects occur. The evidence presented here supports identification of targets which can be used to develop novel treatment strategies to promote soft tissue wound healing and restore mucosal coverage of exposed bone in MRONJ.

Inhibitory Effects of Alendronate on Adhesion and Viability of Preosteoblast Cells on Titanium Discs

Objective  This study aimed to investigate the effects of alendronate (ALN; a bisphosphonate) on adhesion and viability of preosteoblasts using different cell passages on sandblasted and acid-etched (SLA) Ti surfaces.

Materials and Methods  Preosteoblast, MC3T3, cells (passage 42; P42 and passage 62; P62) were cultured with ALN (1 and 5 µM) on cell culture plate for 7 days. Cells were lifted, counted, and seeded on SLA Ti surfaces. Cells were incubated on the discs for 6 hours to examine cell adhesion by using confocal microscopy and for 24 hours to determine cell viability by using MTT assay.

Results  ALN interfered with cell adhesion on Ti surfaces by reducing the cell number in both cell passages. Nuclei of untreated cells showed oval shape, whereas some nuclei of ALN-treated cells demonstrated crescent and condensed appearance. ALN at 1 and 5 µM significantly decreased nuclear area and perimeter in P42, while ALN at 5 µM reduced nuclear area and perimeter in P62. After 24 hours, cells (P42) grown on Ti surfaces showed decreased cell viability when culturing with 5 µM ALN.

Conclusion  ALN reduced cell adhesion and viability of preosteoblasts on Ti surfaces. ALN treatment seemed to exert higher inhibitory effects on nuclear shape and size as well as cell viability in lower cell passage. This led to the reduction in cell to implant surface interaction after encountering bisphosphonate treatment.

Titanium implant alters the effect of zoledronic acid on the behaviour of endothelial cells

OBJECTIVES

To evaluate the effect of zoledronic acid (ZA) on human umbilical vein endothelial cells (HUVECs) attached to different surfaces.

MATERIALS AND METHODS

A total of three groups were evaluated in this study: sandblasting and acid etching (SLA) + HUVECs; mechanically polished (MP) + HUVECs; and plastic cell culture plates + HUVECs. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, surface roughness and water contact angle were tested for titanium surface characterisation. ZA was added at different concentrations (0, 1, 10, 50 and 100 μM). Cell adhesion, proliferation, viability, apoptosis and gene expression were evaluated.

RESULTS

Mechanically polished and SLA surfaces showed negative effects on cell adhesion and proliferation and promoted cell apoptosis with 100 μM ZA (p < .05). The highest expression of intercellular adhesion molecule-1 (ICAM-1) and angiopoietin-1 was found on SLA surfaces (p < .01). The lowest expression of platelet-endothelial cell adhesion molecule-1 and ICAM-1 was found on MP surfaces (p < .05). A significant decrease in von Willebrand factor was detected on MP and SLA surfaces (p < .001).

CONCLUSIONS

Zoledronic acid has an anti-angiogenic effect on HUVECs attached to titanium implants, while the SLA surface might stimulate HUVECs to express angiogenic and adhesive factor genes despite ZA treatment.

Influence of bisphosphonates on oral implantology: Sodium alendronate and zoledronic acid enhance the synthesis and activity of matrix metalloproteinases by gingival fibroblasts seeded on titanium

OBJECTIVE

This study aimed to assess the influence of the bisphosphonates zoledronic acid and sodium alendronate on MMP-2 and MMP-9 synthesis and activity by gingival fibroblasts seeded onto titanium substrate.

DESIGN

Titanium discs were placed in 24-well cell culture plates and gingival fibroblasts were seeded (1 × 10⁵ cells/discs) on them using Dulbecco's Modified Eagle's Medium (DMEM) + 10 % fetal bovine serum (FBS) for 24 h. After this period, a fresh serum-free DMEM containing zoledronic acid or sodium alendronate at 0.5 μM, 1 μM or 5 μM was applied on the cells for an additional of 24 h. Serum-free DMEM and tumor necrosis factor alpha (TNF-α) were used as negative and positive controls, respectively. MMP-2 and MMP-9 synthesis and activity were determined by ELISA (Enzyme-Linked Immunosorbent Assay) and conventional/in situ zymography. Quantitative data were analyzed by one-way ANOVA and Tukey's tests (α = 0.05). The in situ zymography data were qualitatively described.

RESULTS

Despite both bisphosphonates increased the MMPs synthesis, this effect was significant higher in zoledronic acid groups. MMPs activity resembled by gelatinolytic activity was also enhanced by sodium alendronate and zoledronic acid in a similar pattern.

CONCLUSIONS

Zoledronic acid and sodium alendronate increased in a dose-dependent manner MMP-2 and MMP-9 synthesis by gingival fibroblasts seeded on titanium. MMP-2 activity was up-regulated by zoledronic acid treatment.

Effects of EGF-coated titanium surfaces on adhesion and metabolism of bisphosphonate-treated human keratinocytes and gingival fibroblasts

OBJECTIVE

To assess the effects of epidermal growth factor (EGF)-coated titanium (Ti) discs on the adhesion and metabolism of keratinocytes and gingival fibroblasts exposed to nitrogen-containing bisphosphonates.

MATERIALS AND METHODS

Keratinocytes and fibroblasts were seeded (1 × 10⁵ cells/disc) on Ti discs coated with EGF (100 nM). After 24 h, cells were exposed or not to sodium alendronate (SA) or zoledronic acid (ZA) at different concentrations (0 = control, 0.5, 1, or 5 μM) for 48 h. Cell adhesion to the substrates was evaluated by fluorescence microscopy. Cell viability (alamarBlue, n = 6) and synthesis of vascular endothelial growth factor (VEGF), matrix metalloproteinase-2 (MMP-2), and keratinocytes growth factor (KGF) (ELISA, n = 6) were assessed. Data were statistically analyzed by one-way ANOVA and Tukey tests (α = 0.05).

RESULTS

Higher cell adhesion rate was observed when keratinocytes and fibroblasts were seeded onto EGF-coated discs in comparison to uncoated discs. ZA treatment hindered the adhesion of both cell lines on the Ti discs as well as reduced the viability and synthesis of VEGF, KGF and MMP-2 by cells (p < 0.05). SA treatment did not affect cell viability, but interfered negatively on the adhesion and synthesis of EGF and KGF by the cells (p < 0.05). EGF-coated surface increased cell viability and synthesis of growth factors as well as downregulated the synthesis of MMP-2 in comparison to control (p < 0.05).

CONCLUSION

EGF applied on Ti surface improves the biological responses of oral mucosa cells exposed to SA and ZA.

CLINICAL RELEVANCE

EGF-coating on titanium may be a suitable strategy to improve oral mucosa cellular events related to biological sealing, especially for patients under bisphosphonate therapy.

Photobiomodulation using LLLT and LED of cells involved in osseointegration and peri-implant soft tissue healing

This study evaluated the influence of photobiomodulation (PBM) using low-level laser therapy (PBM/LLLT) or light-emitting diode (PBM/LED) therapy on peri-implant tissue healing. A laboratory model was used to assess the adhesion and metabolism of osteoblasts (SaOs-2), human gingival fibroblasts (HGF), and normal oral keratinocytes (NOK) seeded on a titanium (Ti) surface. After seeding the cells on disks of Ti placed in wells of 24-well plates, three irradiations were performed every 24 h at energy density of 3 J/cm². For PBM/LLLT, a LaserTABLE device was used with a wavelength of 780 nm and 25 mW, while for PBM/LED irradiation, a LEDTABLE device was used at 810 nm, 20 mW, at a density of 3 J/cm². After irradiations, the number of cells (NC) attached and spread on the Ti surface, cell viability (CV), total protein (TP), and collagen (Col) synthesis were assessed. Alkaline phosphate activity (ALP) was evaluated only for SaOs-2. Data were submitted to ANOVA complemented by Turkey statistical tests at a 5% significance level. PBM significantly increased adherence of NOK to the Ti surface, while no significant effect was observed for SaOs-2 and HGF. PBM positively affected CV, as well as Col and TP synthesis, in distinct patterns according to the cell line. Increased ALP activity was observed only in those cells exposed to PBM/LLLT. Considering cell specificity, this investigation reports that photobiomodulation with low-power laser and LED at determined parameters enhances cellular functions related to peri-implant tissue healing in a laboratory model.

Histomorphometric Evaluation of Peri-Implant Bone Response to Intravenous Administration of Zoledronate (Zometa®) in an Osteoporotic Rat Model

We evaluated the response to peri-implant bone placed in the femoral condyle of osteoporotic rats, following intravenous zoledronate (ZOL) treatment in three settings: pre-implantation (ZOL-Pre), post-implantation (ZOL-Post), and pre- + post-implantation (ZOL-Pre+Post). Twenty-four female Wistar rats were ovariectomized (OVX). After 12 weeks, the rats received titanium implants in the right femoral condyle. ZOL (0.04 mg/kg, weekly) was administered to six rats 4 weeks pre-implantation and was stopped at implant placement. To another six rats, ZOL was given post-implantation and continued for 6 weeks. Additional six rats received ZOL treatment pre- and post-implantation. Control animals received weekly saline intravenous injections. At 6 weeks post-implantation, samples were retrieved for histological evaluation of the percentage of bone area (%BA) and of the percentage of bone-to-implant contact (%BIC). BA% for ZOL-Pre (29.6% ± 9.0%) and ZOL-Post (27.9% ± 5.6%) rats were significantly increased compared to that of the controls (17.3% ± 3.9%, p < 0.05). In contrast, ZOL-Pre+Post rats (20.4% ± 5.0%) showed similar BA% compared to Saline controls (p = 0.731). BIC% revealed a significant increase for ZOL-Post (65.8% ± 16.9%) and ZOL-Pre+Post (68.3% ± 10.0%) rats compared with that of Saline controls (43.3% ± 9.6%, p < 0.05), while ZOL-Pre rats (55.6% ± 19%) showed a BIC% comparable to that of Saline controls (p = 0.408). Our results suggest that receiving intravenous ZOL treatment before or after implant placement enhances peri-implant bone responses in terms of bone area. However, the effect of different ZOL treatment regimens on BIC% was found to be inconclusive.

Influence of Implant Material and Surface on Mode and Strength of Cell/Matrix Attachment of Human Adipose Derived Stromal Cell

A fundamental step for cell growth and differentiation is the cell adhesion. The purpose of this study was to determine the adhesion of different cell lineages, adipose derived stromal cells, osteoblasts, and gingival fibroblast to titanium and zirconia dental implants with different surface treatments. Primary cells were cultured on smooth/polished surfaces (titanium with a smooth surface texture (Ti-PT) and machined zirconia (ZrO₂-M)) and on rough surfaces (titanium with a rough surface texture (Ti-SLA) and zirconia material (ZrO₂-ZLA)). Alterations in cell morphology (f-actin staining and SEM) and in expression of the focal adhesion marker were analysed after 1, 7, and 14 days. Statistical analysis was performed by one-way ANOVA with a statistical significance at p = 0.05. Cell morphology and cytoskeleton were strongly affected by surface texture. Actin beta and vimentin expressions were higher on rough surfaces (p < 0.01). Vinculin and FAK expressions were significant (p < 0.05) and increased over time. Fibronectin and laminin expressions were significant (p < 0.01) and did not alter over time. Strength of cell/material binding is influenced by surface structure and not by material. Meanwhile, the kind of cell/material binding is regulated by cell type and implant material.

Cytotoxicity of acrylic resin-based materials used to fabricate interim crowns

STATEMENT OF PROBLEM

If the components in the acrylic resins used to fabricate interim crows are cytotoxic, they can interfere with the integrity of the adjacent periodontal tissue and the dentin-pulp complex.

PURPOSE

The purpose of this in vitro study was to assess the cytotoxicity of resin-based materials used to prepare interim crowns.

MATERIAL AND METHODS

The following materials were used in this study: CAR, conventional acrylic resin powder and liquid; BR, bis-acrylic resin; and PAR, pressed acrylic resin of the CAD-CAM type. Glass disks were used as the control (Co). Oral epithelial cells (NOK) were seeded on glass disks and standardized disks prepared with the resins under study. After incubation for 24 hours, the cells were analyzed for viability (Alamar Blue and Live or Dead), adhesion, and morphology (SEM and fluorescence), as well as epidermal growth factor synthesis (EGF-ELISA). The surface roughness (Ra) of test specimens was evaluated under a confocal microscope. The data were submitted to ANOVA and the Tukey HSD statistical tests (α=.05).

RESULTS

The highest Ra value was observed in BR in comparison with CAR, PAR, and Co (P<.05). The highest viability, adhesion, and EGF synthesis values were determined for the cells in contact with PAR (P<.001).

CONCLUSIONS

The computer-aided design and computer-aided manufacturing (CAD-CAM)-type resin favored adhesion, metabolism, and epithelial cell proliferation, and it was therefore considered cytocompatible.

Synthetic Calcium Phosphate Ceramics as a Potential Treatment for Bisphosphonate-Related Osteonecrosis of the Jaw

(1) Background: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is one of the most often seen side effects in patients treated with nitrogen-containing bisphosphonates (BPs), a post-surgical non-healing wound condition. Since calcium phosphate (CP) compounds are able to adsorb zoledronate (ZOL) when used as a drug delivery vehicle, we aimed to verify if these ceramics might have a potential protective effect for soft tissues surrounding surgical osseous wounds. (2) Methods: The chemical reaction between ZOL and CP compounds was evaluated through ultraviolet-visible spectroscopy and elemental analysis. A primary culture of human gingival fibroblasts (HGF) was established as a model to evaluate the cytotoxicity of the association of ZOL (5–500 μM) and of ZOL/biphasic calcium phosphates (BCP). Metabolic activity, cell viability, types of cell death, the cell cycle through, and the migration ability of human gingival fibroblasts were evaluated. (3) Results: ZOL was adsorbed by biphasic calcium phosphate compounds in an aqueous solution. The HGF were sensitive to ZOL toxicity; nevertheless, ZOL/BCP showed a significant protective effect regarding metabolic activity, cell viability, and cell migration. (4) Conclusions: BCP interaction with ZOL reduces or abolishes its toxicity in HGF. This finding represents a potential solution for BRONJ in the case of patients undergoing therapy with ZOL.