Clodronate stimulates osteoblast differentiation in ST2 and MC3T3-E1 cells and rat organ cultures

Medication-related osteonecrosis of the jaw (MRONJ): a review of pathogenesis hypothesis and therapy strategies

Medication-related osteonecrosis of the jaw (MRONJ), a severe side effect caused by antiresorptive antiangiogenic medication, particularly bisphosphonates (BPs), has become a challenging disease with serious and profound effects on the physical and mental health of patients. Although it occurs with high frequency and is harmful, the exact mechanism of MRONJ remains unknown, and systematic and targeted approaches are still lacking. Maxillofacial surgeons focus on the etiology of osteonecrosis in the mandible and maxilla as well as the appropriate oral interventions for high-risk patients. Adequate nursing care and pharmacotherapy management are also crucial. This review provides a current overview of the clinicopathologic feature and research of MRONJ caused by BPs, with an emphasis on the potential mechanisms and current therapy and prevention strategies of the disease. We are of the opinion that an in-depth comprehension of the mechanisms underlying MRONJ will facilitate the development of more precise and efficacious therapeutic approaches, resulting in enhanced clinical outcomes for patients.

Bisphosphonates as Radiopharmaceuticals: Spotlight on the Development and Clinical Use of DOTAZOL in Diagnostics and Palliative Radionuclide Therapy

Bisphosphonates are therapeutic agents that have been used for almost five decades in the treatment of various bone diseases, such as osteoporosis, Paget disease and prevention of osseous complications in cancer patients. In nuclear medicine, simple bisphosphonates such as 99mTc-radiolabelled oxidronate and medronate remain first-line bone scintigraphic imaging agents for both oncology and non-oncology indications. In line with the growing interest in theranostic molecules, bifunctional bisphosphonates bearing a chelating moiety capable of complexing a variety of radiometals were designed. Among them, DOTA-conjugated zoledronate (DOTAZOL) emerged as an ideal derivative for both PET imaging (when radiolabeled with 68Ga) and management of bone metastases from various types of cancer (when radiolabeled with 177Lu). In this context, this report provides an overview of the main medicinal chemistry aspects concerning bisphosphonates, discussing their roles in molecular oncology imaging and targeted radionuclide therapy with a particular focus on bifunctional bisphosphonates. Particular attention is also paid to the development of DOTAZOL, with emphasis on the radiochemistry and quality control aspects of its preparation, before outlining the preclinical and clinical data obtained so far with this radiopharmaceutical candidate.

Phytochemical Analysis, Antioxidant and Bone Anabolic Effects of Blainvillea acmella (L.) Philipson

Blainvillea acmella (L.) Philipson [Asteraceae] (B. acmella) is an important medicinal plant native to Brazil, and it is widely known as a toothache plant. A plethora of studies have demonstrated the antioxidant activities of B. acmella and few studies on the stimulatory effects on alkaline phosphatase (ALP) secretion from bone cells; however, there is no study on its antioxidant and anabolic activity on bone cells. The study aimed to evaluate the phytochemical contents of aqueous and ethanol extracts of B. acmella using gas chromatography mass spectrometry (GCMS) and liquid chromatography time of flight mass spectrometry (LCTOFMS) along with the total phenolic (TPC) and flavonoid (TFC) contents using Folin-Ciocalteu and aluminum colorimetric methods. The extracts of B. acmella leaves were used to scavenge synthetic-free radicals such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) assays. The bone anabolic effects of B. acmella extracts on MC3T3-E1 cells were measured with 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazoium bromide (MTT) at 1, 3, 5, and 7 days, Sirius-red and ALP at 7 and 14 days, and Alizarin Red S at 14 and 21 days. Comparatively, ethanol extract of B. acmella (BaE) contributed higher antioxidant activities (IC50 of 476.71 µg/ml and 56.01 ± 6.46 mg L-ascorbic acid/g against DPPH and FRAP, respectively). Anabolic activities in bone proliferation, differentiation, and mineralization were also higher in B. acmella of ethanol (BaE) than aqueous (BaA) extracts. Positive correlations were observed between phenolic content (TPC and TFC) to antioxidant (ABTS and FRAP) and anabolic activities. Conversely, negative correlations were present between phenolic content to antioxidant (DPPH) activity. These potential antioxidant and bone anabolic activities in BaE might be due to the phytochemicals confirmed through GCMS and LCTOFMS, revealed that terpenoids of α-cubebene, cryophyllene, cryophyllene oxide, phytol and flavonoids of pinostrobin and apigenin were the compounds contributing to both antioxidant and anabolic effects in BaE. Thus, B. acmella may be a valuable antioxidant and anti-osteoporosis agent. Further study is needed to isolate, characterize and elucidate the underlying mechanisms responsible for the antioxidant and bone anabolic effects.

Effect of technetium-99 conjugated with methylene diphosphonate (99 Tc-MDP) on OPG/RANKL/RANK system in vitro

BACKGROUND

RANKL and RANK play an important role in jaw resorption during the development of the ameloblastomas. Therefore, the aim of this study was to explore the effect of ⁹⁹ Tc-MDP on OPG/RANKL/RANK system on RAW264.7 and MC3T3-E1 cell lines in vitro and provide the theoretical basis for the clinical treatment of the jaw ameloblastoma.

METHODS

Different concentrations of ⁹⁹ Tc-MDP were used to treat RAW264.7 and MC3T3-E1 cell lines. The cell proliferative inhibition rate was analyzed by CCK-8. Cell apoptosis and cell cycle were detected by flow cytometry. Western blot was used to detect the expression of OPG, RANKL, and RANK.

RESULTS

Treatment of RAW264.7 cell lines with different concentrations of ⁹⁹ Tc-MDP had inhibitory effects and decreased the expression of RANK protein. The cell proliferation of ⁹⁹ Tc-MDP on MC3T3-E1 cell lines was stronger at 48 hours than at 24 hours except for 100 μg/mL concentration group. Compared with the concentration of 0.01 μg/mL, the treatment of MC3T3-E1 cells with 100 μg/mL ⁹⁹ Tc-MDP showed that the cell proliferative effect decreased at 24 hours and 48 hours (P < 0.05). After treatment with 0.01 μg/mL ⁹⁹ Tc-MDP, the expression of OPG in MC3T3-E1 cells was significantly increased (P < 0.05). Compared with 0.01 μg/mL, the expression of RANKL was decreased after treatment with 100 μg/mL ⁹⁹ Tc-MDP (P < 0.05).

CONCLUSION

⁹⁹ Tc-MDP can induce apoptosis of RAW264.7 cells and inhibit the expression of RANK protein. The effect of 0.01 μg/mL of low concentration of ⁹⁹ Tc-MDP can promote the proliferation of MC3T3-E1 cells and increase the expression of OPG and RANKL protein. ⁹⁹ Tc-MDP may have adjuvant therapeutic effects on the treatment of jaw ameloblastoma.

Osteoblast as a target of anti-osteoporotic treatment

Osteoblasts are mesenchymal cells that play a key role in maintaining bone homeostasis; they are responsible for the production of extracellular matrix proteins, regulation of matrix mineralization, control of bone remodeling and regulate osteoclast differentiation. Osteoblasts have an essential role in the pathogenesis of many bone diseases, particularly osteoporosis. For many decades, the main current available treatments for osteoporosis have been represented by anti-resorptive drugs, such as bisphosphonates, which act mainly by inhibiting osteoclasts maturation, proliferation and activity; nevertheless, in recent years much attention has been paid on anabolic aspects of osteoporosis treatment. Many experimental evidences support the hypothesis of direct effects of the classical anti-resorptive drugs also on osteoblasts, and recent progress in understanding bone physiology have led to the development of new pharmacological agents such as anti-sclerostin antibodies and teriparatide which directly target osteoblasts, inducing anabolic effects and promoting bone formation.

Do topical applications of bisphosphonates improve bone formation in oral implantology? A systematic review

Background

The aim of this systematic literature review was to evaluate the feasibility of topical bisphosphonate application for preserving/enhancing alveolar bone in oral implantology.

Material and Methods

An electronic search was conducted in the PubMed/Medline, EMBASE, Scopus, Web of knowledge, and Google-Scholar databases for articles dated from January 2000 to December 2016. Two reviewers assessed the quality of the studies independently.

Results

A total of 154 abstracts were identified, of which 18 potentially relevant articles were selected; a final total of nine papers were included for analysis. Comparison of the findings of the selected studies was made difficult by the heterogeneity of the articles, all of them animal research papers that showed heterogeneity in the methodologies used and a high or moderate risk of bias.

Conclusions

The topical application of bisphosphonate solution would appear to favor new bone formation in alveolar defects, and boosts the regenerative capacities of biomaterials resulting in increased bone density.

Key words:Alveolar bone, bone regeneration, topical application, biomaterial, bisphosphonates.

Pharmacologic Modulation of Clodronate in Local Therapy of Periodontal and Implant Inflammation

Bisphosphonates are drugs used in the treatment of a variety of osteometabolic diseases. Recently they have been the object of research and studies on their potential application in dentistry and orthopedics. In particular, clodronate (non-aminobisphosphonates) has been studied, due to its reversible activity in comparison to apoptotic osteoclasts, the intrinsic action which stimulates the differentiation and activity of the osteoblasts, their antinflammatory activity, antipain and antioxidant action, represent the rational to estimate their clinical efficacy, for local use in dentistry, implatology, orthopaedic, rheumatology, oncology and dermatology.

The novel bisphosphonate disodium dihydrogen-4-[(methylthio) phenylthio] methanebisphosphonate increases bone mass in post-ovariectomy rats

The novel bisphosphonate (BP) disodium dihydrogen-4-[(methylthio) phenylthio] methanebisphosphonate (MPMBP) is a non-nitrogen-containing BP with an antioxidant side chain that possesses anti-inflammatory properties. We investigated the systemic effects of this compound on bone loss induced by ovariectomy (OVX) in adult rats. Micro-computed tomography revealed that MPMBP increased bone mass and density in both the metaphysis and diaphysis, and improved the structural properties important for mechanical strength of osteoporotic bone. Sequential bone labeling with tetracycline and calcein indicated that MPMBP decreased longitudinal growth of the primary spongiosa (PS), but stimulated cortical bone formation in the diaphysis. MPMBP increased type I collagen accumulation in the PS, and decreased the number and size of adipocytes in the bone marrow, suggesting inhibition of increased bone marrow adipogenesis induced by OVX. Furthermore, MPMBP reduced the number of bone resorbing cathepsin K-positive osteoclasts induced by OVX. These results suggest that MPMBP could improve bone loss induced by estrogen deficiency. Both stimulation of bone formation and inhibition of bone resorption might play a role in the increase in bone mass and bone density after MPMBP treatment.

Lower dosage of aspirin promotes cell growth and osteogenic differentiation in murine bone marrow stromal cells

Background/purpose

The effect of aspirin on bone regeneration remains controversial. This study aimed to determine the effect of various concentrations of aspirin on cell viability, osteogenic differentiation, cell cycle, and apoptosis on ST2 cells to find an effective range of aspirin for bone regeneration induction.

Materials and methods

Cell viability was measured with MTT assay after being stimulated with aspirin for 1 day, 2 days, 3 days, 5 days, and 7 days. Alkaline phosphatase (ALP) activity was measured after cells were treated for 1 day, 3 days, and 7 days. Expression of runt-related transcription factor 2 (Runx-2) was evaluated using Western-blot analysis at 3 days and 7 days. Flow cytometry was used for cell cycle and apoptosis measurement after cells were treated for 48 hours.

Results

Lower concentrations of aspirin (1μΜ and 10μM) promoted cell growth and increased ALP levels and Runx-2 expression, while higher concentrations (100μΜ and 1000μΜ) inhibited cell growth (P < 0.05), and lost their effect on ALP activity after 3 days, while even showing an inhibitory effect on the expression of Runx-2. Aspirin at a concentration of 100μM promoted cell mitosis from the S phase to the G2/M phase, and 1000μM arrested the cell cycle in the resting phase G0/G1 (P < 0.05). Parallel apoptosis/necrosis studies showed the percentage of cells in apoptosis decreased dramatically at any dose of aspirin.

Conclusion

A lower dosage of aspirin could promote ST2 cell growth, osteogenic differentiation, and inhibit their apoptosis which indicates that aspirin can be used as an alternative for bone regeneration.

Fabrication of pluronic and methylcellulose for etidronate delivery and their application for osteogenesis

Novel hydrogels were prepared by blending 4% (w/w) methylcellulose (MC) with various concentrations of 12, 14, 16, 18 and 20% (w/w) pluronic F127 (PF) to form injectable implant drug delivery systems. The blends formed gels using lower concentrations of PF compared to when using PF alone. Etidronate sodium (EDS) at a concentration of 4×10(-3)M was loaded into these blends for producing an osteogenesis effect. The pure gels or EDS loaded gels exhibited cytocompatibility to both the osteoblast (MC3T3-E1) and myoblast (C2C12) cell lines whereas the gels of 16PF, 18PF and 20PF were very cytotoxic to the cells. The EDS loaded gels demonstrated significantly greater alkaline phosphatase (ALP) activities compared to the pure gels. The longer exposure time periods of the samples to the cells, the greater was the ALP activity. These EDS loaded gels significantly increased proliferation of both cell lines thus indicating a bone regeneration effect. The PF/MC blends prolonged the in vitro release of EDS for more than 28 days. Based on the in vitro degradation test, the MC extensively improved the gel strength of the PF and delayed the degradation of the gels thus making them more functional for a sustained drug delivery for osteogenesis.

Small molecules and their controlled release that induce the osteogenic/chondrogenic commitment of stem cells

Stem cell-based tissue engineering plays a significant role in skeletal system repair and regenerative therapies. However, stem cells must be differentiated into specific mature cells prior to implantation (direct implantation may lead to tumour formation). Natural or chemically synthesised small molecules provide an efficient, accurate, reversible, and cost-effective way to differentiate stem cells compared with bioactive growth factors and gene-related methods. Thus, investigating the influences of small molecules on the differentiation of stem cells is of great significance. Here, we review a series of small molecules that can induce or/and promote the osteogenic/chondrogenic commitment of stem cells. The controlled release of these small molecules from various vehicles for stem cell-based therapies and tissue engineering applications is also discussed. The extensive studies in this field represent significant contributions to stem cell-based tissue engineering research and regenerative medicine.

Rebamipide delivered by brushite cement enhances osteoblast and macrophage proliferation

Many of the bioactive agents capable of stimulating osseous regeneration, such as bone morphogenetic protein-2 (BMP-2) or prostaglandin E2 (PGE2), are limited by rapid degradation, a short bioactive half-life at the target site in vivo, or are prohibitively expensive to obtain in large quantities. Rebamipide, an amino acid modified hydroxylquinoline, can alter the expression of key mediators of bone anabolism, cyclo-oxygenase 2 (COX-2), BMP-2 and vascular endothelial growth factor (VEGF), in diverse cell types such as mucosal and endothelial cells or chondrocytes. The present study investigates whether Rebamipide enhances proliferation and differentiation of osteoblasts when delivered from brushite cement. The reactive oxygen species (ROS) quenching ability of Rebampide was tested in macrophages as a measure of bioactivity following drug release incubation times, up to 14 days. Rebamipide release from brushite occurs via non-fickian diffusion, with a rapid linear release of 9.70% ± 0.37% of drug per day for the first 5 days, and an average of 0.5%-1% per day thereafter for 30 days. Rebamipide slows the initial and final cement setting time by up to 3 and 1 minute, respectively, but does not significantly reduce the mechanical strength below 4% (weight percentage). Pre-osteoblast proliferation increases by 24% upon exposure to 0.4 uM Rebamipide, and by up to 73% when Rebamipide is delivered via brushite cement. Low doses of Rebamipide do not adversely affect peak alkaline phosphatase activity in differentiating pre-osteoblasts. Rebamipide weakly stimulates proliferation in macrophages at low concentrations (118 ± 7.4% at 1 uM), and quenches ROS by 40-60%. This is the first investigation of Rebamipide in osteoblasts.

Pharmacological management of osteogenesis

Osteogenesis and bone remodeling are complex biological processes that are essential for the formation of new bone tissue and its correct functioning. When the balance between bone resorption and formation is disrupted, bone diseases and disorders such as Paget's disease, fibrous dysplasia, osteoporosis and fragility fractures may result. Recent advances in bone cell biology have revealed new specific targets for the treatment of bone loss that are based on the inhibition of bone resorption by osteoclasts or the stimulation of bone formation by osteoblasts. Bisphosphonates, antiresorptive agents that reduce bone resorption, are usually recommended as first-line therapy in women with postmenopausal osteoporosis. Numerous studies have shown that bisphosphonates are able to significantly reduce the risk of femoral and vertebral fractures. Other antiresorptive agents indicated for the treatment of osteoporosis include selective estrogen receptor modulators, such as raloxifene. Denosumab, a human monoclonal antibody, is another antiresorptive agent that has been approved in Europe and the USA. This agent blocks the RANK/RANKL/OPG system, which is responsible for osteoclastic activation, thus reducing bone resorption. Other approved agents include bone anabolic agents, such as teriparatide, a recombinant parathyroid hormone that improves bone microarchitecture and strength, and strontium ranelate, considered to be a dual-action drug that acts by both osteoclastic inhibition and osteoblastic stimulation. Currently, anti-catabolic drugs that act through the Wnt-β catenin signaling pathway, serving as Dickkopf-related protein 1 inhibitors and sclerostin antagonists, are also in development. This concise review provides an overview of the drugs most commonly used for the control of osteogenesis in bone diseases.

Bisphosphonates: effects on osteoblast

PURPOSE

Bisphosphonates are synthetic analogues of pyrophosphate usually used in treating bone disorders such as osteoporosis, Paget's disease, fibrous dysplasia, hypercalcemia of malignancy, and inflammation-related bone loss. Though therapeutic effects of bisphosphonates depend primarily on their inhibitory effect on osteoclasts, increasing attention is being given to other effector cells, such as osteoblasts. This review focuses on the presumed effect of bisphosphonates on osteoblasts.

METHODS

A review of the literature was conducted to evaluate the pharmacodynamic effects of bisphosphonates including inhibition of osteoclasts and apoptosis of osteocytes and osteoblasts as well as their potential stimulatory effects on the proliferation of osteoblasts.

RESULTS

Studies have demonstrated that bisphosphonates may stimulate proliferation of osteoblasts and inhibit apoptosis of osteocytes and osteoblasts.

CONCLUSION

Considering that osteoblasts may be involved in bone disorders, such as osteoporosis, osteopetrosis, osteogenesis imperfecta, and Paget's disease, and that bisphosphonates may stimulate proliferation of osteoblasts and inhibit apoptosis of osteocytes and osteoblasts, it is conceivable that a role for bisphosphonates exists in these diseases beyond merely the osteoclast influence.

Novel actions of bisphosphonates in bone: preservation of osteoblast and osteocyte viability

Bisphosphonates stop bone loss by inhibiting the activity of bone-resorbing osteoclasts. However, the effect of bisphosphonates on bone mass cannot completely explain the reduction in fracture incidence observed in patients treated with these agents. Recent research efforts provided an explanation to this dichotomy by demonstrating that part of the beneficial effect of bisphosphonates on the skeleton is due to prevention of osteoblast and osteocyte apoptosis. Work of our group, independently confirmed by other investigators, demonstrated that bisphosphonates are able to prevent osteoblast and osteocyte apoptosis in vitro and in vivo. This prosurvival effect is strictly dependent on the expression of connexin (Cx) 43, as demonstrated in vitro using cells lacking Cx43 or expressing dominant-negative mutants of the protein as well as in vivo using Cx43 osteoblast/osteocyte-specific conditional knock-out mice. Remarkably, this Cx43-dependent survival effect of bisphosphonates is independent of gap junctions and results from opening of Cx43 hemichannels. Hemichannel opening leads to activation of the kinases Src and extracellular signal-regulated kinases (ERKs), followed by phosphorylation of the ERK cytoplasmic target p90(RSK) kinase and its substrates BAD and C/EBPβ, resulting in inhibition of apoptosis. The antiapoptotic effect of bisphosphonates is separate from the effect of the drugs on osteoclasts, as analogs that lack antiresorptive activity are still able to inhibit osteoblast and osteocyte apoptosis in vitro. Furthermore, a bisphosphonate analog that does not inhibit osteoclast activity prevented osteoblast and osteocyte apoptosis and the loss of bone mass and strength induced by glucocorticoids in mice. Preservation of the bone-forming function of mature osteoblasts and maintenance of the osteocytic network, in combination with lack anticatabolic actions, open new therapeutic possibilities for bisphosphonates in the treatment of osteopenic conditions in which decreased bone resorption is not desired.

The effect of the alendronate on OPG/RANKL system in differentiated primary human osteoblasts

Alendronate is a well-established treatment for osteoporosis and suppresses bone resorption by a direct effect on osteoclasts and their precursors. The effect of alendronate on osteoclasts is produced, at least in part, by the receptor activator of nuclear factor kappaB ligand (RANKL) and the osteoprotegerin (OPG) synthesized by the osteoblasts. This study analyzes the effect of alendronate in cell viability, alkaline phosphatase (ALP) activity and RANKL and OPG expression in primary human osteoblasts (hOB). Alendronate at concentrations lower than 10⁻⁵ M did not have a toxic effect on hOB in vitro and did not modify the ALP activity at least for 72 h. Alendronate did not change OPG expression in basal, 10% fetal bovine serum (FBS), and vitamin D-treated cultures. Similar results were observed at the protein level. Unexpectedly, alendronate at 10⁻⁷ and 10⁻⁵ M concentrations increased the RANKL expression with the presence of vitamin D in differentiated hOB, and this induction of RANKL mRNA levels by alendronate was dose-dependent. However, this effect was not observed in basal and 10% FBS culture conditions. Thus, we conclude that alendronate does not affect the ALP activity and OPG gene expression in differentiated hOB, but may increase RANKL gene expression induced by vitamin D.

Effect of the anti-diabetic drug metformin on bone mass in ovariectomized rats

Recent studies have reported bone loss in the patients with diabetes and a direct osteogenic effect of metformin on osteoblast-like cells in culture. In this study, we investigated the action of metformin on bone mass in ovariectomized (OVX) rats. Three months after either a sham surgery or bilateral ovariectomy, thirty-two female Sprague-Dawley rats were randomly assigned into four groups: (1) Sham group; (2) OVX group; (3) OVX+metformin (50mg/kg/day) group; and (4) OVX+metformin (100mg/kg/day) group. After 2 months of oral administration with or without metformin, tibiae were harvested for dual energy X-ray absorptiometry, micro-computed tomography (micro-CT) and histology analysis, while the bone marrow cells from tibiae were collected for measurement of the mRNAs expressions for three osteoblast genes and estrogen receptors alpha by the use of real-time RT-PCR. We found that the impaired bone density and quality induced by bilateral ovariectomy were significantly improved by the treatment of metformin (both 50 and 100mg/kg/day), and this action could be partly mediated by regulating bone marrow cells development through induction of mechanisms regulating osteoblast markers core binding factor a1 and LDL receptor-related protein 5. These findings provide new evidence that the anti-diabetic drug metformin has a direct inhibition effect on bone loss in OVX rats, in addition to its well-documented osteogenic potency in vitro.

The effect of the alendronate on OPG/RANKL system in differentiated primary human osteoblasts

Alendronate is a well-established treatment for osteoporosis and suppresses bone resorption by a direct effect on osteoclasts and their precursors. The effect of alendronate on osteoclasts is produced, at least in part, by the receptor activator of nuclear factor kappaB ligand (RANKL) and the osteoprotegerin (OPG) synthesized by the osteoblasts. This study analyzes the effect of alendronate in cell viability, phosphatase alkaline (ALP) activity and RANKL, and OPG expression in primary human osteoblasts (hOB). Alendronate at concentrations lower than 10(-5) M did not have a toxic effect on hOB in vitro and did not modify the ALP activity at least for 72 h. Alendronate did not change OPG expression in basal, 10% FBS, and vitamin D-treated cultures. Similar results were observed at the protein level. Unexpectedly, alendronate at 10(-7) and 10(-5) M concentrations increased the RANKL expression with the presence of vitamin D in differentiated hOB and this induction of RANKL mRNA levels by alendronate was dose-dependent. However, this effect was not observed in basal and 10% FBS culture conditions. Thus, we conclude that alendronate does not affect the ALP activity and OPG gene expression in differentiated hOB, but may increase RANKL gene expression induced by vitamin D.

Weekly clodronate treatment prevents bone loss and vertebral fractures in women with subclinical Cushing's syndrome

INTRODUCTION

Chronic mild endogenous glucocorticoid excess has been shown to cause bone loss and to increase fracture risk in both post-menopausal and premenopausal women. Currently, it is unclear if patients with subclinical Cushing's syndrome (SCS) with osteoporosis or osteopenia may benefit from antiresorptive treatment and the type of therapy to be given.

OBJECTIVE

This pilot randomized study was aimed at evaluating the effects of 12-month im administration of clodronate (100 mg every week) on vertebral and femoral bone mineral density (BMD), bone turnover markers and on subjective pain in premenopausal women with SCS due to adrenal incidentalomas.

METHODS

Forty-six women (age, 43.1+/-7.7 yr) with SCS due to adrenal incidentaloma and osteoporosis/osteopenia were randomized to receive clodronate plus supplement of Calcium (500 mg daily) and Vitamin D3 (800 mg daily) (group 1, no.=23) or supplements only (group 2, no.=23). Both groups were similar in terms of age, body mass index, cortisol levels, BMD values, and bone turnover markers. All of the women were re-evaluated after 12 months.

RESULTS

After 12 months of treatment, in group 1, a significant increase in lumbar BMD occurred (p=0.04), while bone turnover markers decreased by about one third (p<0.05). In group 2, bone turnover markers did not change and BMD values slightly decreased (p=ns). The differences in bone turnover markers and in lumbar BMD between the two groups were significant (p<0.05, all). No new vertebral fracture occurred in group 1, while in group 2 the spine radiographies revealed 2 new fractures and a worsening of two pre-existent fractures. An improvement in subjective back pain, assessed by visual analogue scale pain score was observed in group 1 (from 4.3+/-2.7 to 2.9+/-2.0; p<0.05) but not in group 2 (from 4.4+/-3.1 to 4.2+/-3.4; p=ns). No significant changes occurred in cortisol secretion or clinical picture of the SCS during the study.

CONCLUSIONS

Intramuscular administration of clodronate effectively increased lumbar BMD values, preserved bone mass at the femoral neck, stabilized vertebral fracture index, and decreased subjective back pain in pre-menopausal women with SCS. Since the untreated group continued to lose bone, antiresorptive treatment should be considered in patients with SCS, according to the prevision of surgical treatment, prevalent fractures, BMD values, age, concomitant morbidities, and desire for pregnancy.

Effects of Alendronate on the Proliferation and Osteogenic Differentiation of MG-63 Cells

Previous studies of the direct actions of bisphosphonates on bone have mainly been limited to their effects on bone-resorbing osteoclasts and little is known about the direct effects of bisphosphonates on osteoblasts. Here we report the direct effects of alendronate on the proliferation and osteogenic differentiation of the MG-63 osteoblast-like cell line. Cell proliferation was determined with the MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay, osteogenic differentiation was evaluated with an alkaline phosphatase bioassay and by analysis of gene expression by reverse transcription-polymerase chain reaction, and the extent of calcium deposition was measured using Alizarin Red S staining. Alendronate significantly increased cell numbers over control values, with the greatest effect at 10−8 M. Alkaline phosphatase activity and gene expression of bone morphogenetic protein 2, type I collagen and osteocalcin were increased after alendronate treatment. Alendronate also stimulated calcium deposition. We conclude that alendronate, apart from inhibiting osteoclastic bone resorption, is also a promoter of osteoblast proliferation and maturation.

Effects of alendronate and pamidronate on cultured rat metatarsal bones: failure to prevent dexamethasone-induced growth retardation

Bisphosphonates are widely used anti-resorptive drugs in the adult population. In children, their use has mainly been limited to patients with osteogenesis imperfecta. However, the powerful effects of bisphosphonates on bone turnover have raised concern about their long-term effects on the growing skeleton. We aimed to study the effects of two commonly used bisphosphonates, alendronate (Aln) and pamidronate (Pam) on normal bone growth as well as their potential to prevent glucocorticoid-induced growth retardation. Effects on bone growth were studied in fetal rat metatarsal bones (day E20) that were cultured for 5-47 days and measured every 2-7 days. Cellular mechanisms were investigated in metatarsal bones and also in the human chondrocytic cell line HCS-2/8. Chondrocyte viability (WST-1), proliferation (BrdU incorporation), differentiation (collagen type X immunohistochemistry) and apoptosis (TUNEL and Cell Death ELISA) were determined. At a clinically relevant concentration of bisphosphonates (1 microM), metatarsal bone growth was stimulated by both Aln (p<0.001 for length and p<0.05 for width) and Pam (p<0.05 for both length and width) from day 19 of culture. The growth-stimulatory effect was associated with increased chondrocyte proliferation (+21% with Aln and +24% with Pam), while cell differentiation and apoptosis were not affected. Despite the finding that both Aln and Pam (1 muM) rescued HCS-2/8 cells from undergoing dexamethasone-induced apoptosis, neither of them was able to prevent dexamethasone-induced growth retardation of fetal rat metatarsal bones. Aln and Pam have the capacity to stimulate the growth of cultured fetal rat metatarsal bones; an effect associated with increased proliferation of growth plate chondrocytes. Our experimental data suggest that bisphosphonates are ineffective in preventing glucocorticoid-induced growth retardation. Nevertheless, based on our in vitro data, both Aln and Pam appear safe to use in growing children, at least with regard to their effects on linear bone growth.

Alendronate has an anabolic effect on bone through the differentiation of mesenchymal stem cells

We committed MSCs to differentiate into either osteoblasts or adipocytes and examined the effect of ALN on both adipogenesis and osteoblastogenesis. ALN inhibited adipogenesis while promoting osteoblast differentiation and activity. Our results reveal a new anabolic effect of ALN in differentiating bone marrow cells.

INTRODUCTION

Alendronate (ALN) prevents bone loss in postmenopausal patients through the regulation of osteoclastic activity. However, it has also proven to be effective in older adults where the pathophysiological mechanism is the predominance of adipogenesis over osteoblastogenesis. The aim of this study is to determine the in vitro effect of ALN on both osteoblastogenesis and adipogenesis.

MATERIALS AND METHODS

Human mesenchymal stem cells (MSCs) were plated at a density of 5 x 10(5) cells/well in 100-cm2 dishes containing MSC growth media. After confluence, cells were committed to differentiate adding either adipogenic or osteogenic media with and without 1,25(OH)2D3 (10(-8) M) and supplemented with ALN at increasing concentrations (10(-9) to 10(-7) M). Untreated differentiating MSCs were used as control. Alkaline phosphatase (ALP), oil red O, and Alizarin red staining were performed at timed intervals (weeks 1 and 2). Additionally, levels of expression of both osteogenesis and adipogenesis transcription factors were measured in protein extracts. Finally, the effect of ALN on PPARgamma2 nuclear activation complex was assessed.

RESULTS

We found that ALN has a significant and dose-dependent effect on osteoblastogenesis. This effect was not modified by the presence of 1,25(OH)2D3 in the medium. Furthermore, adipogenic differentiation of MSCs was affected by addition of both ALN and 1,25(OH)2D3 to the media as confirmed by phenotype changes and lower number of lipid droplets. Finally, expression of adipogenic transcription factors and PPARgamma2 activation were reduced in adipose differentiating MSCs treated with either ALN or ALN + 1,25(OH)2D3.

CONCLUSIONS

This study shows a potential anabolic effect of ALN in vitro through the stimulation of osteogenic differentiation of MSCs. Additionally, a previously unknown inhibitory effect of ALN on bone marrow adipogenesis was also found.

Alternative bisphosphonate targets and mechanisms of action

As the number of bisphosphonates continues to increase, they have found widespread use in an increasing number of clinical conditions. Ongoing examination of their targets and mechanisms of action has revealed that this surprisingly diverse class of drugs has effects beyond those first described for osteoclasts. These additional targets include osteoblasts, osteocytes, angiogenesis, and gammadelta T lymphocytes of the human immune system. The immune system effects are specifically targeted to gammadelta T cells and are reminiscent of the effects seen after ingestion of tea beverage. BP effects on such alternate targets may explain not only their antiresorptive effect, but also their effect on bone quality, tumors, and microbes.

Systemic and local ibandronate enhance screw fixation

The trauma involved with inserting implants into bone leads to an activation of the inflammatory response and an activation of osteoclasts. In addition, apoptosis of osteocytes in the surrounding area has been implicated in further activation of osteoclasts. If the balance between resorption and bone formation shortly after implantation favours resorption, an impairment of early fixation might ensue. Because bisphosphonates inhibit resorption, this study analyses whether they can improve early fixation. Stainless steel screws (M 1.7) were inserted into the tibiae of 76 male Sprague-Dawley rats. Daily subcutaneous injections of ibandronate (3 microg) or saline were given to 20 rats. The remaining rats received ibandronate or saline directly applied into the drill hole before the screw was inserted. Tibiae were harvested at 14 days. Mechanical tests were performed on 50 tibiae. Systemically treated tibiae were tested for pull-out strength alone. Locally treated tibiae were tested for either pull-out or torque resistance. The remaining 18 tibiae were prepared for histology. Systemic ibandronate increased the pull-out force at failure by 30% (p=0.04). Local treatment increased the force at failure by 15% (p=0.02) and stiffness by 28% (p=0.01). In the removal torque measurements, local ibandronate increased the torque-moment at failure by 60% (p=0.04), and the maximum friction moment by 51% (p=0.04). Energy for turning the screw 1/4 revolution was increased by 68% (p=0.02). These results demonstrate that early remodeling events plays an important role in screw fixation, and that systemic or local bisphosphonate treatment could be an effective pharmacological path to improve early implant fixation.