The impact of bisphosphonates on the osteoblast proliferation and Collagen gene expression in vitro

The Potential of Enamel Matrix Derivative in Countering Bisphosphonate-Induced Effects in Osteoblasts

The suppressive effect of bisphosphonates (BPs) on bone metabolism is considered to be a major cause of medication-related osteonecrosis of the jaw (MRONJ). Enamel matrix derivative (EMD) stimulates and activates growth factors, leading to the regeneration of periodontal tissues. In this study, we aimed to explore the potential of EMD in reversing the detrimental effects of BPs on human fetal osteoblasts (hFOBs) and osteosarcoma-derived immature osteoblasts (MG63s) by assessing cell viability, apoptosis, migration, gene expression, and protein synthesis. While the suppressive effect of zoledronate (Zol) on cell viability and migration was observed, the addition of EMD significantly mitigated this effect and enhanced cell viability and migration. Furthermore, an increased apoptosis rate induced by Zol was decreased with the addition of EMD. The decreased gene expression of alkaline phosphatase (ALP), osteocalcin (OC), and the receptor activator of nuclear factors kappa-B ligand (RANKL) caused by BP treatment was reversed by the co-addition of EMD to hFOB cells. This trend was also observed for ALP and bone sialoprotein (BSP) levels in MG63 cells. Furthermore, suppressed protein levels of OC, macrophage colony-stimulating factor (M-CSF), BSP, and type 1 collagen (COL1) were recovered following the addition of EMD. This finding suggests that EMD could mitigate the effects of BPs, resulting in the recovery of cell survival, migration, and gene and protein expression. However, the behavior of the osteoblasts was not fully restored, and further studies are necessary to confirm their effects at the cellular level and to assess their clinical usefulness in vivo for the prevention and treatment of MRONJ.

Dose-dependent effects of zoledronic acid on the osteogenic differentiation of human bone marrow stem cells (hBMSCs)

Recent studies have shown that bisphosphonates can also impact osteoblasts besides osteoclasts. This study aimed to evaluate the effects of different concentrations of Zoledronic acid (ZA) during the osteogenic differentiation of human Bone Marrow Stem Cells (hBMSCs) in vitro. Thus, osteogenic differentiation of hBMSCs was conducted with different concentrations of Zoledronic Acid (ZA) (0, 0.1, 1.0, and 5.0 μM) for the first 3 days. Cell metabolism was quantified at 1-, 3-, 7-, and 14 days. At 7- and 14-days, the following analyses were performed: 1) mineralization nodule assay, 2) LIVE/DEAD™, 3) cell adhesion and spreading, 4) alkaline phosphatase (ALP) activity, and 5) qPCR analysis for RUNX-2), ALPL, and COL1 A1. Data were analyzed by ANOVA 2-way, followed by Tukey's post hoc test (p < 0.05). Cell metabolism (3-, 7-, and 14-days) (p < 0.001), mineralization (7-, 14-days) (p < 0.001), and ALP activity (14-days) (p < 0.001) were reduced in ZA 5.0 µM when compared to control (no ZA). Also, ZA 5.0 µM downregulated the expression of RUNX2 at 7- and 14-days (p < 0.001). It is possible to conclude that ZA (5.0 µM) can impair hBMSC differentiation into osteoblasts and interferes with its mineralization phase.

Nano-formulations for bone-specific delivery of siRNA for CrkII silencing-induced regulation of bone formation and resorption to maximize therapeutic potential for bone-related diseases

CrkII, a member of the adaptor protein family, is known to participate in bone homeostasis via the regulation of osteoclasts and osteoblasts. Therefore, silencing CrkII would beneficially impact the bone microenvironment. In this study, CrkII siRNA encapsulated by a bone-targeting peptide (AspSerSer)₆-liposome was evaluated for its therapeutic applications using a receptor activator of nuclear factor kappa-B ligand (RANKL)-induced bone loss model. (AspSerSer)₆-liposome-siCrkII maintained its gene-silencing ability in both osteoclasts and osteoblasts in vitro and significantly reduced osteoclast formation while increasing osteoblast differentiation in vitro. Fluorescence image analyses showed that the (AspSerSer)₆-liposome-siCrkII was present largely in bone, where it remained present for up to 24 hours and was cleared by 48 hours, even when systemically administrated. Importantly, microcomputed-tomography revealed that bone loss induced by RANKL administration was recovered by systemic administration of (AspSerSer)₆-liposome-siCrkII. Collectively, the findings of this study suggest that (AspSerSer)₆-liposome-siCrkII is a promising therapeutic strategy for the development of treatments for bone diseases, as it overcomes the adverse effects derived from ubiquitous expression via bone-specific delivery of siRNA.

Significance of bisphosphonates on angiogenesis in vivo and their effect under geranyl-geraniol addition - could it alter the treatment of bisphosphonate-associated necrosis of the jaw?

PURPOSE

The aim of this study was to contribute to the understanding of the inhibitory effects of bisphosphonates on tissues, with a special focus on angiogenesis. Referring to bisphosphonate-associated osteonecrosis of the jaw (BP-ONJ), it should be shown that the local addition of the isoprenoid geranyl-geraniol (GGOH) prevents vascularization processes.

METHODS

A mouse model with n = 24 animals which received an injection of a collagen matrix was used. In 4 subgroups (n = 6), we examined the effect of zoledronate on the sprouting of capillary-like structures into the matrix, with and without the presence of geranyl-geraniol, as well as testing against control groups with PBS injections or collagen matrix containing PBS instead of GGOH. This was followed by a histological evaluation of the capillary-like structures.

RESULTS

Zoledronate inhibits the sprouting of blood vessels into a collagen matrix in vivo; in the presence of GGOH this effect is significantly weakened by a factor of 3.9 (p = 0.00068).

CONCLUSION

This work commits to the investigation of the pathophysiology of BP-ONJ and shows a possible causal therapeutic path via the topical application of GGOH.

The Effects of Polyphenol, Tannic Acid, or Tannic Acid in Combination with Pamidronate on Human Osteoblast Cell Line Metabolism

Background: This study investigates the effect of tannic acid (TA) combined with pamidronate (PAM) on a human osteoblast cell line. Methods: EC₅₀ for TA, PAM, and different combination ratios of TA and PAM (25:75, 50:50, 75:25) were measured by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The combination index value was utilized to analyze the degree of drug interaction, while trypan blue assay was applied to analyze the cells proliferation effect. The mineralization and detection of bone BSP and Osx genes were determined via histochemical staining and PCR test, respectively. Results: The EC₅₀ of osteoblasts treated with TA and a 75:25 ratio of TA and PAM were more potent with lower EC₅₀ at 0.56 µg/mL and 0.48 µg/mL, respectively. The combination of TA and PAM (75:25) was shown to have synergistic interaction. On Day 7, both TA and PAM groups showed significantly increased proliferation compared with control and combination groups. On Day 7, both the TA and combination-treated groups demonstrated a higher production of calcium deposits than the control and PAM-treated groups. Moreover, on Day 7, the combination-treated group showed a significantly higher expression of BSP and Osx genes than both the TA and PAM groups. Conclusion: Combination treatment of TA and PAM at 75:25 ameliorated the highest enhancement of osteoblast proliferation and mineralization as well as caused a high expression of BSP and Osx genes.

Alendronate and omeprazole in combination reduce angiogenic and growth signals from osteoblasts

Objective

Due to gastrointestinal side effects of oral bisphosphonates (BPs), proton pump inhibitors (PPIs) are often prescribed. PPIs may enhance the risk of osteonecrosis of the jaw, a rare side effect of BPs. Therefore, the objective of this study was to evaluate the effects of the oral BP alendronate (ALN) and the PPI omeprazole (OME) alone and in combination on primary human osteoblasts and gingival fibroblasts in vitro.

Methods

Human gingival fibroblasts and normal human osteoblasts were incubated with either 5 μM of ALN or 1 μM of OME, or ALN + OME for 1, 3, 7 or 14 days. Effect on viability was evaluated by the lactate dehydrogenase activity in the medium and on proliferation by quantifying 3H-thymidin incorporation. Multianalyte profiling of proteins in cell culture media was performed using the Luminex 200TM system to assess the effect on selected bone markers and cytokines.

Results

The proliferation of osteoblasts and fibroblasts was reduced upon exposure to ALN + OME. ALN induced an early, temporary rise in markers of inflammation, and OME and ALN + OME promoted a transient decline. An initial increase in IL-13 occurred after exposure to all three options, whereas ALN + OME promoted IL-8 release after 7 days. OME and ALN + OME promoted a transient reduction in vascular endothelial growth factor (VEGF) from osteoblasts, whereas ALN and ALN + OME induced a late rise in VEGF from fibroblasts. Osteoprotegerin release was enhanced by ALN and suppressed by OME and ALN + OME.

Conclusions

ALN + OME seemed to exaggerate the negative effects of each drug alone on human osteoblasts and gingival fibroblasts. The anti-proliferative effects, modulation of inflammation and impairment of angiogenesis, may induce unfavorable conditions in periodontal tissue facilitating development of osteonecrosis.

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Alendronate and omeprazole reduce proliferation in osteoblasts and fibroblasts.

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Unchanged viability after exposure to either drug or the combination

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Omeprazole, alone and combined with alendronate, cause impairment of angiogenesis.

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Alendronate promotes an initial, transient increase in pro-inflammatory cytokines.

Bisphosphonates Reduce Smoking-Induced Osteoporotic-Like Alterations by Regulating RANKL/OPG in an Osteoblast and Osteoclast Co-Culture Model

Co-culture models have become mandatory for obtaining better insights into bone homeostasis, which relies on the balance between osteoblasts and osteoclasts. Cigarette smoking (CS) has been proven to increase the risk of osteoporosis; however, there is currently no proven treatment for osteoporosis in smokers excluding cessation. Bisphosphonates (BPs) are classical anti-osteoclastic drugs that are commonly used in examining the suitability of bone co-culture systems in vitro as well as to verify the response to osteoporotic stimuli. In the present study, we tested the effects of BPs on cigarette smoke extract (CSE)-affected cells in the co-culture of osteoblasts and osteoclasts. Our results showed that BPs were able to reduce CSE-induced osteoporotic alterations in the co-culture of osteoblasts and osteoclasts such as decreased matrix remodeling, enhanced osteoclast activation, and an up-regulated receptor activator of nuclear factor (NF)-kB-ligand (RANKL)/osteoprotegerin (OPG) ratio. In summary, BPs may be an effective alternative therapy for reversing osteoporotic alterations in smokers, and the potential mechanism is through modulation of the RANKL/OPG ratio.

Pathogenesis of medication-related osteonecrosis of the jaw: a comparative study of in vivo and in vitro trials

Objective This study was performed to determine whether the results of prevailing in vivo and in vitro studies offer a reliable model for investigation of medication-related osteonecrosis of the jaw (MRONJ). Methods Embase, Medline, and the Cochrane Library were searched for articles published from September 2003 to June 2017 involving experimental approaches to the pathogenesis of MRONJ. In vivo and in vitro trials were analyzed with respect to the scientific question, study design, methodology, and results. Results Of 139 studies, 87, 46, and 6 conducted in vivo, in vitro, and both in vivo and in vitro experiments, respectively. Rats, mice, dogs, minipigs, sheep, and rabbits were the preferred animal models used. Osteoblasts, osteoclasts, fibroblasts, keratinocytes, macrophages, and human umbilical vein endothelial cells were the preferred cell types. Zoledronate, alendronate, ibandronate, and risedronate were the most frequent bisphosphonates used. MRONJ was most reliably induced in minipigs because of the close relationship with human bone physiology. In vitro studies showed that reduced viability, growth, and migration of cells in the bone and soft tissues were causative for MRONJ. Other than exposed jawbone after tooth extraction, no reliable cofactors were found. Conclusion The minipig is the most suitable animal model for MRONJ.

Paradoxical side effects of bisphosphonates on the skeleton: What do we know and what can we do?

Bisphosphonates are considered the most effective drugs for controlling adult and pediatric osteolytic diseases. Although they have been used successfully for many years, several side effects, such as osteonecrosis of the jaw, delayed dental eruption, atypical femoral fracture, and alterations to the bone growth system, have been described. After an overview of nitrogenous bisphosphonate, the purpose of this article is to describe their mechanisms of action and current applications, review the preclinical and clinical evidence of their side effects in the skeleton ("what we know"), and describe current recommendations for preventing and managing these effects ("what we can do"). Finally, promising future directions on how to limit the occurrence of these side effects will be presented.

Bone tissue response following local drug delivery of bisphosphonate through titanium oxide nanotube implants in a rabbit model

OBJECTIVES

The objective of this study was to evaluate whether surface chemistry-controlled TiO₂ nanotube structures may serve as a local drug delivery system for zoledronic acid improving implant-bone support.

METHODS

Twenty-four screw-shaped Ti implants with surface chemistry-controlled TiO₂ nanotube structures were prepared and divided into a zoledronic acid-formatted test and a native control group. The implants were inserted into contra-lateral femoral condyles in 12 New Zealand White rabbits. Bone support was evaluated using resonance frequency analysis (RFA) and removal torque (RTQ), as well as histometric analysis following a 3-weeks healing interval.

RESULTS

Zoledronic acid-formatted TiO₂ nanotube test implants showed significantly improved implant stability and osseointegration measured using RFA and RTQ compared with control (p < 0.05), and showed significantly enhanced new bone formation within the root of the threads compared with control (p < 0.05).

CONCLUSIONS

TiO₂ nanotube implants may prove to be a significant delivery system for drugs or biologic agents aimed at supporting local bone formation. Additional study of candidate drugs/agents, optimized dosage and release kinetics is needed prior to evaluation in clinical settings.

Cytoprotective effects of melatonin on zoledronic acid-treated human osteoblasts

OBJECTIVE

To evaluate the cytoprotective effects of melatonin (MLT) on zoledronic acid (ZA)-treated human osteoblasts.

METHODS

Human osteoblasts were exposed to ZA (1, 5, 10, 50, 100 and 300 μM) and MLT (1, 10, 50, 100 y 200 μM) for 24, 48 and 72 h of incubation, to evaluate their effects on cell viability.

RESULTS

As ZA concentration increased, greater reductions in cell viability of human osteoblasts were induced whether at 24, 48 or 72 h incubation. At 24 h incubation with MLT, greatest cell viability was obtained when low dose of MLT was applied (without significant differences); 48 and 72 h incubation presented the greatest cell viability with the highest MLT concentrations (100 and 200 μM). MLT at concentrations of 100 and 200 μM would appear to have a certain cytoprotective effect on ZA-treated human osteoblasts with low concentrations of ZA (1 y 5 μM), whether at 24, 48 or 72 h; however, at ZA concentrations ≥10 μM the possible cytoprotective effects of MLT were low at 24 h incubation.

CONCLUSIONS

MLT has a cytoprotective effect on ZA-treated human osteoblasts and could represent a promising preventative alternative for patients at risk of bisphosphonate-related osteonecrosis of the jaw.

Doses effects of zoledronic acid on mineral apatite and collagen quality of newly-formed bone in the rat's calvaria defect

Due to their inhibitory effects on resorption, bisphosphonates are widely used in the treatment of diseases associated to an extensive bone loss. Yet, little is known about bisphosphonates effects on newly-formed bone quality. In the present study, adult male Sprague-Dawley rats (n=80) with a bone defect calvaria area were used and short-term effects of zoledronic acid (ZA) were studied on the healing bone area. Three ZA treatments were tested by using either: 1°) a low single dose (120μgZA/kg, n=10; equivalent to human osteoporosis treatment), 2°) a low fractionated doses (20μgZA/kg daily for 6days either a total of 120μg/kg, n=15), and 3°) a high fractionated doses, (100μgZA/kg weekly for 6weeks, n=15; equivalent to 6months of human bone metastasis treatment). For each treatment, a control "vehicle" treatment was performed (with an identical number of rats). After ZA administration, the intrinsic bone material properties were evaluated by quantitative backscattered electron imaging (qBEI) and Raman microspectroscopy. Neither single nor fractionated low ZA doses modify the intrinsic bone material properties of the newly-formed bone compared to their respective control animals. On the opposite, the high ZA treatment resulted in a significant decrease of the crystallinity (-25%, P< 0.05) and of the hydroxyproline-to-proline ratio (-30%, P<0.05) in newly-formed bones. Moreover, with the high ZA treatment, the crystallinity was positively correlated with the hydroxyproline-to-proline ratio (ρ=0.78, P<0.0001). The present data highlight new properties for ZA on bone formation in a craniofacial defect model. As such, ZA at high doses disrupted the apatite crystal organization. In addition, we report here for the first time that high ZA doses decreased the hydroxyproline-to-proline ratio suggesting that ZA may affect the early collagen organization during the bone healing.

Zoledronic acid increases the circulating soluble RANKL level in mice, with a further increase in lymphocyte-derived soluble RANKL in zoledronic acid- and glucocorticoid-treated mice stimulated with bacterial lipopolysaccharide

The nitrogen-containing bisphosphonate (BP) zoledronic acid (ZA) is a potent antiresorptive drug used in conjunction with standard cancer therapy to treat osteolysis or hypercalcemia due to malignancy. However, it is unclear how ZA influences the circulating levels of bone remodeling factors. The aim of this study was to evaluate the effects of ZA on the serum levels of soluble receptor activator of NF-kB ligand (sRANKL) and osteoprotegerin (OPG). The following four groups of C57BL/6 mice were used (five mice per group): (1) the placebo+phosphate-buffered saline (PBS) group, in which placebo-treated mice were injected once weekly with PBS for 4weeks; (2) the placebo+ZA group, in which placebo-treated mice were injected once weekly with ZA for 4weeks; (3) the prednisolone (PSL)+PBS group, in which PSL-treated mice were injected once weekly with PBS for 4weeks; and (4) the PSL+ZA group, in which PSL-treated mice were injected once weekly with ZA for 4weeks. At the 3-week time point, all mice were subjected to oral inflammatory stimulation with bacterial lipopolysaccharide (LPS). The sera of these mice were obtained every week and the levels of sRANKL and OPG were measured using enzyme-linked immunosorbent assay. At the time of sacrifice, femurs were prepared for micro-computed tomography (micro-CT), histological, and histomorphometric analyses. Our data indicated that ZA administration remarkably reduced bone turnover and significantly increased the basal level of sRANKL. Interestingly, the PSL+ZA group showed a dramatically elevated sRANKL level after LPS stimulation. In contrast, the PSL+ZA group in nonobese diabetic mice with severe combined immunodeficiency disease (NOD-SCID mice), which are characterized by the absence of functional T- and B-lymphocytes, showed no increase in the sRANKL level. Our data suggest that, particularly with combination treatment of ZA and glucocorticoids, surviving lymphocytes might be the source of inflammation-induced sRANKL. Thus, circulating sRANKL levels might be modulated by ZA.

Donepezil regulates energy metabolism and favors bone mass accrual

The autonomous nervous system regulates bone mass through the sympathetic and parasympathetic arms. The sympathetic nervous system (SNS) favors bone loss whereas the parasympathetic nervous system (PNS) promotes bone mass accrual. Donepezil, a central-acting cholinergic agonist, has been shown to down-regulate SNS and up-regulate PNS signaling tones. Accordingly, we hypothesize that the use of donepezil could have beneficial effects in regulating bone mass. To test our hypothesis, two groups of healthy female mice were treated either with donepezil or saline. Differences in body metabolism and bone mass of the treated groups were compared. Body and visceral fat weights as well as serum leptin level were increased in donepezil-treated mice compared to control, suggesting that donepezil effects on SNS influenced metabolic activity. Donepezil-treated mice had better bone quality than controls due to a decrease in osteoclasts number. These results indicate that donepezil is able to affect whole body energy metabolism and favors bone mass in young female WT mice.

PRGF exerts a cytoprotective role in zoledronic acid-treated oral cells

OBJECTIVES

Bisphosphonates-related osteonecrosis of the jaw (BRONJ) is a common problem in patients undergoing long-term administration of highly potent nitrogen-containing bisphosphonates (N-BPs). This pathology occurs via bone and soft tissue mechanism. Zoledronic acid (ZA) is the most potent intravenous N-BP used to prevent bone loss in patients with bone dysfunction. The objective of this in vitro study was to evaluate the role of different ZA concentrations on the cells from human oral cavity, as well as the potential of plasma rich in growth factors (PRGF) to overcome the negative effects of this BP.

MATERIAL AND METHODS

Primary human gingival fibroblasts and primary human alveolar osteoblasts were used. Cell proliferation was evaluated by means of a fluorescence-based method. A colorimetric assay to detect DNA fragmentation undergoing apoptosis was used to determine cell death, and the expression of both NF-κB and pNF-κB were quantified by Western blot analysis.

RESULTS

ZA had a cytotoxic effect on both human gingival fibroblasts and human alveolar osteoblasts. This BP inhibits cell proliferation, stimulates apoptosis, and induces inflammation. However, the addition of PRGF suppresses all these negative effects of the ZA.

CONCLUSIONS

PRGF shows a cytoprotective role against the negative effects of ZA on primary oral cells.

CLINICAL RELEVANCE

At present, there is no definitive treatment for bisphosphonates-related osteonecrosis of the jaw (BRONJ), being mainly palliatives. Our results revealed that PRGF has a cytoprotective role in cells exposed to zoledronic acid, thus providing a reliable adjunctive therapy for the treatment of BRONJ pathology.

Intraoperative detection of viable bone with fluorescence imaging using Visually Enhanced Lesion Scope in patients with bisphosphonate-related osteonecrosis of the jaw: clinical and pathological evaluation

There is no standard surgical protocol of bisphosphonate-related osteonecrosis of the jaws (BRONJ), because of the impossibility to visualize this feature intraoperatively. The aim of this study was to introduce how to provide preoperative labeling of the viable bone with minocycline bone fluorescence technique (MBFT) by using VELscope® and investigate histopathologically.

INTRODUCTION

The American Association of Oral and Maxillofacial Surgeons (AAOMS) and the Japanese Society of Oral and Maxillofacial Surgeons (JSOMS) now recommend a more conservative treatment strategy. There is no standard surgical protocol of bisphosphonate-related osteonecrosis of the jaws (BRONJ) because of the impossibility to visualize this feature intraoperatively. The aim of this study was to introduce a mechanism providing preoperative labeling of a viable bone using minocycline bone fluorescence technique (MBFT) with VELscope® and to histopathologically investigate.

METHODS

This report describes a surgical technique used in six patients with BRONJ who underwent jawbone resection under minocycline bone fluorescence imaging using VELscope®. Subsequently, we investigated and compared the clinical findings using VELscope® and histopathological findings.

RESULTS

Histopathological examinations showed that the non-fluorescent moiety was consistent with the BRONJ lesions.

CONCLUSIONS

The surgical treatments that were exactly performed using MBFT with VELscope® offered successful management of BRONJ. This bone fluorescence helped to define the margins of resection, thus improving surgical therapy for extended osteonecrosis.

Development, validation and characterization of a novel mouse model of Adynamic Bone Disease (ABD)

The etiology of Adynamic Bone Disease (ABD) is poorly understood but the hallmark of ABD is a lack of bone turnover. ABD occurs in renal osteodystrophy (ROD) and is suspected to occur in elderly patients on long-term anti-resorptive therapy. A major clinical concern of ABD is diminished bone quality and an increased fracture risk. To our knowledge, experimental animal models for ABD other than ROD-ABD have not been developed or studied. The objectives of this study were to develop a mouse model of ABD without the complications of renal ablation, and to characterize changes in bone quality in ABD relative to controls. To re-create the adynamic bone condition, 4-month old female Col2.3Δtk mice were treated with ganciclovir to specifically ablate osteoblasts, and pamidronate was used to inhibit osteoclastic resorption. Four groups of animals were used to characterize bone quality in ABD: Normal bone controls, No Formation controls, No Resorption controls, and an Adynamic group. After a 6-week treatment period, the animals were sacrificed and the bones were harvested for analyses. Bone quality assessments were conducted using established techniques including bone histology, quantitative backscattered electron imaging (qBEI), dual energy X-ray absorptiometry (DXA), microcomputed tomography (microCT), and biomechanical testing. Histomorphometry confirmed osteoblast-related hallmarks of ABD in our mouse model. Bone formation was near complete suppression in the No Formation and Adynamic specimens. Inhibition of bone resorption in the Adynamic group was confirmed by tartrate-resistant acid phosphatase (TRAP) stain. Normal bone mineral density and architecture were maintained in the Adynamic group, whereas the No Formation group showed a reduction in bone mineral content and trabecular thickness relative to the Adynamic group. As expected, the No Formation group had a more hypomineralized profile and the Adynamic group had a higher mean mineralization profile that is similar to suppressed bone turnover in human. This data confirms successful replication of the adynamic bone condition in a mouse without the complication of renal ablation. Our approach is the first model of ABD that uses pharmacological manipulation in a transgenic mouse to mimic the bone cellular dynamics observed in the human ABD condition. We plan to use our mouse model to investigate the adynamic bone condition in aging and to study changes to bone quality and fracture risk as a consequence of over-suppressed bone turnover.

Zoledronic acid at subtoxic dose extends osteoblastic stage span of primary human osteoblasts

OBJECTIVE

This study aimed to check the effect of zoledronic acid (ZA) at subtoxic dose on human osteoblasts (HOs) in terms of cell viability, apoptosis occurrence, and differentiation induction. ZA belongs to the family of bisphosphonates (BPs), largely used in the clinical practice for the treatment of bone diseases, often associated with jaw osteonecrosis onset. Their pharmacological action consists in the direct block of the osteoclast-mediated bone resorption along with indirect action on osteoblasts.

MATERIALS AND METHODS

HOs were treated choosing the highest limit concentration (10(-5) M) which does not induce toxic effects. Live/dead staining, flow cytometry, mitochondrial membrane potential assay, osteocalcin western blotting, gp38 RT-PCR, collagen type I, PGE2, and IL-6 ELISA assays were performed.

RESULTS

Similar viability level between control and ZA-treated samples is found along with no significant increase of apoptotic and necrotic cells in ZA-treated sample. To establish if an early apoptotic pathway was triggered, Bax expression and mitochondrial membrane potential were evaluated finding a higher protein expression in control sample and a good integrity of mitochondrial membrane in both experimental points. Type I collagen secretion and alkaline phosphatase (ALP) activity appear increased in ZA-treated sample, osteocalcin expression level is reduced in ZA-treated cells, whereas no modifications of gp38 mRNA level are evidenced. No statistical differences are identified in PGE2 secretion level whereas IL-6 secretion is lower in ZA-treated HOs with respect to control ones.

CONCLUSIONS

These results highlight that ZA, delaying the osteoblastic differentiation process versus the osteocytic lineage, strengthens its pharmacological activity enhancing bone density.

CLINICAL RELEVANCE

The knowledge of ZA effects on osteoblasts at subtoxic dose allows to improve therapeutic protocols in order to strengthen drug pharmacological activity through a combined action on both osteoclastic and osteoblastic cells.

Pharmacophysiology of bone and spinal fusion

BACKGROUND CONTEXT

In recent years, the number of complex spinal surgeries has increased significantly in the elderly population, where the prevalence of low bone density is highest. Consequently, spine surgeons often treat osteoporotic patients who are associated with higher rates of instrumentation failure. Therefore, establishing a successful fusion requires an appropriate substrate for bone formation and local bone remodeling. The fusion process can be supported by therapies that seek to shift the balance of bone homeostasis to increased formation and reduced resorption.

PURPOSE

Thorough understanding of the physiology of bone formation and adjunctive therapies can help improve fusion rates. Therefore, we present a thorough review of the latest pharmacologic agents used to enhance bone strength and surgical spinal fusion.

METHODS

Systematic review of literature.

RESULTS

Current knowledge on bone physiology has led to the development of several pharmacologic agents that enhance bone formation and strengthen the human skeleton. At present, natural supplements of vitamin D and calcium or synthetic medications like bisphosphonates are widely used before and after spine surgeries to enhance bone fusion. Additional physiologic agents, including testosterone, parathyroid hormone, calcitonin, and growth hormone, have been shown to improve bone mass density or spinal fusion in both animal and human studies. As in other medical fields, gene therapy has shown viability and promise with the use of both viral and nonviral vectors.

CONCLUSIONS

Through the understanding of bone physiology, numerous natural and synthetic pharmacologic agents have been developed to enhance the body's skeleton and to improve outcomes of spinal fusion surgery.

Zoledronic acid inhibits human osteoblast activities

BACKGROUND

Bisphosphonates are potent inhibitors of bone resorption. These kinds of drugs, which are used for the treatment of osteolytic diseases, have been associated with the occurrence of oral osteonecrosis, especially in patients over 60 years old. Current studies have demonstrated that the cytotoxic effects of bisphosphonates on osteoblasts play an important role in oral osteonecrosis development.

OBJECTIVE

The aim of this study was to evaluate the effect of long-term application of a highly potent bisphosphonate - zoledronic acid (ZA) - on human osteoblasts in vitro.

METHODS

Human osteoblasts (MG63 cell line) were seeded for 72 h in wells of 24-well plates. The Dulbecco's modified Eagle's medium (DMEM) was then replaced by culture medium without fetal bovine serum (FBS), and the cells were incubated for an additional 24 h, after which ZA was added to the DMEM without FBS and incubated in contact with osteoblasts for 7, 14 or 21 days. Cell viability (CV), total protein production (TPP), alkaline phosphatase (ALP) activity, mineral nodule formation (MNF), and gene expression of ALP and osteocalcin (OCN), as well as cell morphology by scanning electronic microscopy, were evaluated. Data were statistically analyzed by Kruskal-Wallis and Mann-Whitney tests, with a significance level of 5%.

RESULTS

The cytotoxic effects of ZA on osteoblasts were characterized by reduction of CV, TPP, ALP and MNF production. In addition, ZA MNF caused a decrease in gene expression of ALP and OCN, as well as intense cell morphology alterations. All these negative effects of ZA were concentration and period dependent.

CONCLUSION

Both concentrations of ZA (1 and 5 μM) caused cytotoxic effects to osteoblasts which reduced the production and expression of proteins that play an important role in bone matrix synthesis and mineralization.

The cytotoxic effects of three different bisphosphonates in-vitro on human gingival fibroblasts, osteoblasts and osteogenic sarcoma cells

INTRODUCTION

Osteonecrosis of the jaw (ONJ) is an emerging condition in patients undergoing long-term administration of bisphosphonates (BP) for the treatment of osteoporosis and hypercalcaemia associated with malignancy, multiple myeloma, and metastatic breast and prostate cancers. This is a follow-up study, its purpose was to examine the effects in-vitro of intravenous zoledronic acid (ZOL) and pamidronate (PAM) and oral alendronate (FOS) on the human oral cavity using gingival fibroblasts and osteoblasts cells and, in addition, osteogenic sarcoma cells (SaOS-2-cells).

MATERIALS AND METHODS

Human gingival fibroblasts, osteoblasts and SaOS-2-cells were seeded on multiple 6-well plates at a density of 5 × 10(5)cells in a 4-week cell culture. Four different concentrations (1, 5, 10, 20 μM) of each BP (ZOL, PAM, FOS) and pyrophosphate were used in this study.

RESULTS

All BP decreased collagen production and lowered cell proliferation in-vitro. ZOL was the component with most inhibitory effect.

CONCLUSION

The findings in this study suggest that ZOL, PAM and FOS generally diminish cell proliferation and collagen production of human gingival fibroblasts, osteoblasts and SaOS-2-cells. The present follow-up study shows that not only ZOL and PAM but also FOS have a strong inhibitory effect on collagen production and cell survival in-vitro.

Design and construction of two yeast shuttle vectors containing human procollagen genes expression cassette for expression in yeast

Collagens are the most abundant proteins in the human body. Their main function is to provide structural and mechanical support for the tissues, but they are also involved in a number of other biological functions including cell attachment, migration and differentiation. Collagens and gelatins are widely used in pharmaceutical and medical applications. Every year, more than 50,000 tons of collagen and gelatin are used in medical applications. These materials may have some viral and prion impurity and/or stimulate allergic response in human body. Therefore, scientists have produced human collagen in recombinant systems. In this study we have constructed two yeast shuttle vectors containing human procollagen genes expression cassette for expression in yeast. Total RNA was extracted from human skin fibroblast cell line, and cDNA synthesis was done by oligo dt. Then gene fragments were amplified from the cDNA with the necessary changes by Polymerase Chain Reaction (PCR). Finally they were cloned in yeast vector pPICZαA containing regulatory sequences for expressing and secreting the polypeptide product. Two yeast shuttle vectors containing human COL1A1 and COL1A2 expression cassettes were created. Final constructs were confirmed by enzymatic digestion, PCR of desired fragment and sequencing. The yeast shuttle vectors containing human COL1A1 and COL1A2 can be transferred into the yeast in the later stages to determine the scale of expression.