The effects of bisphosphonates on osteoblasts in vitro

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.

Alendronato de sódio tópico associado ao osso bovino liofilizado no reparo ósseo

Resumo Introdução O osso bovino inorgânico é o enxerto mais utilizado na Odontologia, tendo como desvantagem longo tempo de integração ao leito receptor. Os bifosfonatos têm sido utilizados para modular a quantidade e a qualidade do osso regenerado e diminuir o tempo de integração do enxerto. Objetivo Avaliar o efeito do bifosfonato alendronato de sódio (ALN) 0,5%, associado ou não ao osso bovino inorgânico, na reparação de defeitos ósseos. Material e método Dois defeitos ósseos foram confeccionados na calvária de 12 coelhos, sendo a cavidade esquerda/experimental preenchida com: GI = osso bovino inorgânico (Bio-Oss®); GII = Bio-Oss® + ALN 0,5%; GIII = ALN 0,5%; e a cavidade direita por coágulo sanguíneo (controle). Os animais foram mortos aos 60 dias pós-operatórios. Por meio de análise histomorfométrica calculou-se o percentual de osso neoformado e remanescente do biomaterial em relação à área total do defeito. Resultado Osso neoformado: GI = 38,16 ± 15,44%; GII = 55,77 ± 16,75%; GII I = 60,28 ± 11,45%. Controle = 45,11 ± 11,09%. Remanescente do enxerto: GI = 7,02 ± 5,36% e GII = 16,59 ± 9,56%. Não houve diferença quanto ao percentual de osso neoformado entre os grupos (ANOVA p = 0,15512; teste de Tukey F = 2,089). O percentual de remanescente do enxerto também foi estatisticamente semelhante entre os grupos GI e GII (teste de Tukey F = 5,019). Conclusão O uso tópico da solução de ALN 0,5% isoladamente ou associado ao osso bovino liofilizado não alterou o percentual de neoformação óssea nem a degradação dos grânulos do enxerto.

A Review on Re-Packaging of Bisphosphonates Using Biomaterials

The need for bone repair and insight into new regeneration therapies as well as improvement of existing regeneration routes is constantly increasing as a direct consequence of the rise in the number of trauma victims, musculoskeletal disorders, and increased life expectancy. Bisphosphonates (BPs) have emerged as a class of drugs with proven efficacy against many bone disorders. The most recent ability of this class of drugs is being explored in its anti-cancer ability. However, despite the pharmacological success, there are certain shortcomings that have circumvented this class of the drug. The mediation of biomaterials in delivering bisphosphonates has greatly helped in overcoming some of these shortcomings. This article is focused on reviewing the benefits the bisphosphonates have provided upon getting delivered via the use of biomaterials. Furthermore, the role of bisphosphonates as a potent anticancer agent is also accounted. It is witnessed that employing engineering tools in combination with therapeutics has the potential to provide solutions to bone loss from degenerative, surgical, or traumatic processes, and also aid in accelerating the healing of large bone fractures and problematic non-union fractures. The role of nanotechnology in enhancing the efficacy of the bisphosphonates is also reviewed and innovative approaches are identified.

Coordination Compounds As Multi-Delivery Systems for Osteoporosis

Osteoporosis therapies leveraging bisphosphonates and mineral components (e.g., magnesium, calcium, and strontium) have been raising attention because of their potential for managing this ever-growing disease. The administration of multicomponent therapeutics (combined therapy) in elderly patients is complex and suffers from low patient adherence. Herein, we report an all-in-one combination of four antiosteoporotic components into a new family of coordination complexes: [M₂(H₄alen)₄(H₂O)₂]·1.5H₂O [where M²⁺ = Mg²⁺ (1), (Mg_0.535Ca_0.465)²⁺ (2) and (Mg_0.505Ca_0.450Sr_0.045)²⁺ (3)]. These solid-state complexes were prepared, for the first time, through microwave-assisted synthesis. It is demonstrated that the compounds are capable of releasing their antiosteoporotic components, both in conditions that mimic the path along the gastrointestinal tract and in long periods under physiological conditions (pH ∼7.4). More importantly, when administered in low concentrations, the compounds did not elicit a cytotoxic effect toward liver, kidney, and osteoblast-like cell lines. Besides, it is important to highlight the unique coordination complex with four bone therapeutic components, [(Mg_0.505Ca_0.450Sr_0.045)₂(H₄alen)₄(H₂O)₂]·1.5H₂O (3), which significantly promoted osteoblast metabolic activity up to ca. 1.4-fold versus the control group. These findings bring this type of compounds one-step closer to be considered as an all-in-one and more effective treatment for managing chronic bone diseases, prompting further research on their therapeutic properties.

Immobilization of BMP-2, BMP-7 and alendronic acid on titanium surfaces: Adhesion, proliferation and differentiation of bone marrow-derived stem cells

This study analyzed the influence of titanium (TiO₂ ) surface modifications with two osteogenic proteins (BMP-2, BMP-7) and an anti-osteoclastic drug (alendronic acid [AA]) on sandblasted/acid-etched (SLA) and plain TiO₂ (PT) on cell adhesion, proliferation and differentiation (alkaline phosphatase [AP] and osteocalcin [OC]) of bone-marrow derived stem cells (BMSCs) after 1, 3 and 7 days in-vitro. Initially, AA surfaces showed the highest cell number and surface coverage. At day 3 and 7, BMP and AA-modified surfaces exhibited a significantly enhanced cell growth. For proliferation, at days 3 and 7, an enhancement on BMP-2, BMP-7 and AA-surfaces was seen. At day 7, SLA also showed a higher proliferation when compared to PT. Initially, AP expression was elevated on SLA and AA surfaces. At days 3 and 7, a significant increased AP expression was seen for SLA, BMP-2, BMP-7 and AA discs. For OC, SLA and AA surfaces had the highest expression after 1 day whereas after 3 and 7 days a significant difference was recorded for SLA, BMP-2, BMP-7 and AA. In conclusion, a beneficial biological effect of a chemical immobilization method of BMP-2, BMP-7 and alendronate onto titanium surfaces on BMSCs was proven.

Effects of local application of alendronate on early healing of extraction socket in dogs

OBJECTIVE

The aim of the present study was to assess the effects of alendronate (ALN) on bone remodeling following tooth extraction in a dog model.

MATERIAL AND METHODS

For the study, fifteen male Beagles dogs of approximately 12 months of age were used. Mesial roots of four mandibular premolars were endodontically treated, and the distal roots were removed. ALN concentrations of 0.5, 1, and 2 mg/mL were topically applied for 15 min, while a sterile saline was used as a negative control. After the healing period of 1, 2, and 8 weeks, the samples were analyzed by micro-CT and histology.

RESULTS

Treatment with ALN increased vertical distance between the lingual and the buccal crestal bones. While the ALN-treated sockets had preserved more lingual bone areas, control sockets showed better preservation of the buccal bone areas. ALN treatment resulted in more osteoid formation within the extraction sockets compared with the control. Higher bone volume was found in ALN groups than in the control at 2-week and 8-week healing periods, reaching the significant difference only for the extraction sockets pooled for the ALN treatment.

CONCLUSIONS

Although ALN treatment could not prevent buccal bone resorption following tooth extraction in dogs, it proved beneficial for the preservation of the lingual bone and formation of new bone within the socket. There was no clear relation between the ALN dosages and the alterations within the extraction sockets.

CLINICAL RELEVANCE

ALN affects bone remodeling of the extraction socket. The optimal concentration remains to be determined in future studies.

Antimicrobial photodynamic therapy improves the alveolar repair process and prevents the occurrence of osteonecrosis of the jaws after tooth extraction in senile rats treated with zoledronate

This study evaluated the effects of antimicrobial photodynamic therapy (aPDT) in the alveolar repair of rats with major risk factors for bisphosphonate-related osteonecrosis of the jaws (BRONJ). Senile rats received 0.45 ml of vehicle (VEH and VEH/aPDT) or 0.45 ml of zoledronate (ZOL and ZOL/aPDT) every three days for seven weeks. After three weeks of treatment, the first lower left molar was extracted. VEH/aPDT and ZOL/aPDT were submitted to aPDT on the extraction site at 0, 2 and 4 days postoperatively. Euthanasia was performed 28 days postoperatively and the extraction site was evaluated by clinical, histological, histometric, histochemical and immunohistochemical analysis. ZOL showed tissue repair impairment; lower percentage of newly formed bone tissue (NFBT); higher percentage of non-vital bone tissue (NVBT); fewer mature collagen fibers and increased immunolabeling for tumor necrosis factor (TNFα), interleukin (IL)-1β and IL-6. ZOL/aPDT showed clinical and histological characteristics of the extraction site, percentage of NFBT and percentage of mature collagen fiber similar to VEH. Percentage of NVBT and immunolabeling for inflammatory cytokines in ZOL/aPDT was lower than in ZOL. Immunolabeling for tartarato-resistant acid phosphatase (TRAP) was lower in ZOL and ZOL/aPDT. aPDT in the dental extraction site improves tissue repair process and prevents the occurrence of BRONJ-like lesions after tooth extraction.

Nitrogen Containing Bisphosphonates Impair the Release of Bone Homeostasis Mediators and Matrix Production by Human Primary Pre-Osteoblasts

Bisphosphonates (BPs) represent the first-line treatment for a wide array of bone disorders. Despite their well-known action on osteoclasts, the effects they induce on osteoblasts are still unclear. In order to shed light on this aspect we evaluated the impact of two nitrogen containing bisphosphonates, Alendronate (ALN) and Zoledronate (ZOL), on human primary pre-osteoblasts. At first, we showed an inhibitory effect on cell viability and alkaline phosphatase activity starting from µM concentrations of both drugs. In addition, an inhibitory trend on mineralized nodules deposition was observed. Then low doses of both ALN and ZOL rapidly increased the release of the pro-inflammatory mediators TNFα and IL-1β, while increased DKK-1 and Sclerostin, both inhibitors of osteoblastogenesis. Finally, ALN and 10^-7M ZOL decreased the expression of type I Collagen and Osteopontin, while both drugs slightly stimulated SPARC production. With these results, we would like to suggest a direct inhibitory action on bone-forming cells by nitrogen containing bisphosphonates.

Decreased microRNA-182-5p helps alendronate promote osteoblast proliferation and differentiation in osteoporosis via the Rap1/MAPK pathway

Osteoporosis (OP) is a serious health problem that contributes to osteoporotic structural damage and bone fragility. MicroRNAs (miRNAs) can exert important functions over bone endocrinology. Therefore, it is of substantial significance to clarify the expression and function of miRNAs in bone endocrine physiology and pathology to improve the potential therapeutic value for metabolism-related bone diseases. We explored the effect of microRNA-182-5p (miR-182-5p) on osteoblast proliferation and differentiation in OP rats after alendronate (ALN) treatment by targeting adenylyl cyclase isoform 6 (ADCY6) through the Rap1/mitogen-activated protein kinase (MAPK) signaling pathway. Rat models of OP were established to observe the effect of ALN on OP, and the expression of miR-182-5p, ADCY6 and the Rap1/MAPK signaling pathway-related genes was determined. To determine the roles of miR-182-5p and ADCY6 in OP after ALN treatment, the relationship between miR-182 and ADCY6 was initially verified. Osteoblasts were subsequently extracted and transfected with a miR-182-5p inhibitor, miR-182-5p mimic, si-ADCY6 and the MAPK signaling pathway inhibitor U0126. Cell proliferation, apoptosis and differentiation were also determined. ALN treatment was able to ease the symptoms of OP. miR-182-5p negatively targeted ADCY6 to inhibit the Rap1/MAPK signaling pathway. Cells transfected with miR-182 inhibitor decreased the expression of ALP, BGP and COL I, which indicated that the down-regulation of miR-182-5p promoted cell differentiation and cell proliferation and inhibited cell apoptosis. In conclusion, the present study shows that down-regulated miR-182-5p promotes the proliferation and differentiation of osteoblasts in OP rats through Rap1/MAPK signaling pathway activation by up-regulating ADCY6, which may represent a novel target for OP treatment.

Bisphosphonates hinder osteoblastic/osteoclastic differentiation in the maxillary sinus mucosa-derived stem cells

OBJECTIVES

Although bisphosphonates (BPs) are known to be associated with osteonecrosis of the maxilla, the precise effects of BPs on bone metabolism in human maxillary sinus mucosal cells (HMSMCs) are not yet known. The purposes of this study were to examine the effects of the BPs zoledronate (ZOL) and alendronate (ALN) on osteoblastic and osteoclastic differentiation in HMSMCs and to investigate the signaling pathways involved.

MATERIALS AND METHODS

The effects of ZOL and ALN were assessed for osteoblast differentiation by alkaline phosphatase (ALP) activity, alizarin red staining, and RT-PCR for genes encoding Runx2 and osterix. Receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclast differentiation in bone marrow macrophages (BMMs) was also examined.

RESULTS

ZOL and ALN both suppressed osteoblastic differentiation, as evidenced by their effects on ALP activity, mineralization nodule formation, and the mRNA expression levels of osteoblastic transcript factors. The RANKL/osteoprotegerin ratio in HMSMCs was increased by ALN, whereas ZOL had the opposite effect. Conditioned medium obtained from ALN-treated HMSMCs stimulated osteoclast formation and upregulated NFATc1 expression, whereas conditioned medium from ZOL-treated cells did not. ALN was more cytotoxic and stimulated apoptosis more strongly than ZOL. BPs decreased the protein levels of the non-canonical Wnt signaling protein Wnt5a and calmodulin-dependent kinase II. Moreover, recombinant human Wnt5a reversed the effects of BPs on osteoblastic and osteoclastic differentiation.

CONCLUSION

This study is the first demonstration that BPs exert negative effects on osteoblastic and osteoclastic processes via the non-canonical Wnt pathway in HMSMSCs.

CLINICAL RELEVANCE

It suggests that patients taking BPs during the period of maxillary sinus lifting and amentation should be given special attention.

Would Be Prophylactic Administrations of Low Concentration of Alendronate an Alternative for Improving the Craniofacial Bone Repair? A Preliminary Study Focused in the Period of Cellular Differentiation and Tissue Organization

BACKGROUND

Alendronate (ALN) is a nitrogen-bisphosphonate that may induce an anabolic effect on craniofacial bone repair when administrated in low doses. Based on this premise, this study analyzed the influence of prophylactic low doses of ALN on bone healing in defects created in rabbit mandible.

METHODS

A 5 × 2-mm diameter deep defect was created in the calvaria of 28 rabbits. Fourteen of these rabbits received previously 50 μg/kg of 1% sodium ALN for 4 weeks, while the other rabbits received only 0.9% physiological saline solution (control). Animals were euthanized at 15 and 60 days postsurgery (n = 7), and the data were analyzed using histomorphometry and immunohistochemistry using the anti-CD34, bone morphogenetic protein -2 (BMP-2), and transforming growth factor (TGF)-β1 antibodies.

RESULTS

On the 15th day postsurgery, the specimens that received previous treatment with ALN demonstrated large vascular lumen and intense positivity to CD34 either concentrated in endothelium or cells spread among the reparative tissue. These results coincided with intense positivity for BMP-2+ cells and TGF-β1 that was concentrated in both cells and perivascular area. In contrast, the control group revealed scarce cells that exhibited CD34, BMP-2+, and the TGF-β1 was restricted for perivascular area on well-formed granulation tissue. These patterns of immunohistochemical result, especially found on the 15th day of analysis, seem to be responsible for the development of larger quantities of bone matrix in the specimens that receive ALN on the 60th day postsurgery.

CONCLUSION

These preliminary results showed that the prophylactic administration of low doses of ALN might be an alternative to craniofacial bone craniofacial bone repair because it increases the immunopositivity for TGF-β1 and consequently improves the CD34+ and BMP-2+ cells on reparative sites.

Prolonged use of alendronate alters the biology of cranial repair in estrogen-deficient rats' associated simultaneous immunohistochemical expression of TGF-β1+, α-ER+, and BMPR1B

OBJECTIVES

TGF-β1 is a cytokine that may induce both osteoneogenesis through Runx-2 or fibrosis via the transcription of α-smooth muscle actin (α-SMA). Because it has been previously known that alendronate increases the level of TGF-β1 and that under the usual condition of bone metabolism the estrogen may prevent the fibrotic effect of TGF-β1, the aim of this study was to evaluate if alendronate alters the cellular differentiation process post calvarial surgery in estrogen-deficient specimens.

MATERIALS AND METHODS

A transosseous defect that was 5 mm in diameter was created on the calvarium of each of 32 female rats with previous ovarian-salpingo-oophorectomy. All defects were treated with autografts, and 16 rats received the administration of 1 mg/kg of alendronate three times a week until euthanasia on the 15th and 60th day post surgery. Histomorphometric and immunohistochemical analyses of the expression of TGF-β1, estrogen receptor alpha nuclear (α-ER), α-SMA, BMPR1B, and Runx-2 were performed, and ELISA was used to measure the level of estrogen.

RESULTS

All animals demonstrated low levels of estrogen post ovarian-salpingo-oophorectomy. The histological results demonstrated larger bone matrix deposition in specimens treated with alendronate on the 15th day post surgery. The result was associated with a higher co-expression of TGF-β1, BMPR1B, and Runx-2 when compared with the control group. In addition, on the 60th day post surgery, the increase of bone matrix deposition from 15th to 60th day was discrete in specimens treated with alendronate compared with the control group. This result coincided with the intense simultaneous expression of TGF-β1, α-ER, and α-SMA, whereas the expression of BMPR1B and Runx-2 decreased.

CONCLUSION

The prolonged administration of alendronate altered the cranial repair in ovarian-salpingo-oophorectomized specimens due to the simultaneous occurrence of low estrogen and the presence of TGF-β1+/α-ER+ inducing the presence of α-SMA⁺, whereas BMPR1B and Runx-2 were suppressed.

CLINICAL RELEVANCE

The prolonged administration of alendronate alters osteoneogenesis and induces an unusual microenvironment in the bone that seems to imitate the physiological tissue damage that culminates in the loss of the functional layer of endometrium.

Immune cell profile of dental pulp tissue treated with zoledronic acid

AIM

To characterize the pulp immune cell profile in the teeth of rats treated with zoledronic acid (ZA).

METHODOLOGY

Male Wistar rats (n = 6 per group) received four intravenous infusions of ZA at doses of 0.04, 0.20 or 1.00 mg kg^-1 ZA or saline (control). On the 70th experimental day, they were euthanized. The first right molar was examined microscopically and submitted to toluidine blue reaction and immunohistochemical for CD68, tumour necrosis Factor (TNF)-α, interleukin (IL)-1β, inducible nitric oxide synthase (iNOS), nuclear factor kappa B (NF-kB) and IL-18 binding protein (IL-18 bp). The presence of ectasic/dilated vessels and inflammatory cells was analysed, and mast cells and mononuclear CD68-positive cells were counted along with the intensity of immunostaining (0-3) for inflammatory markers in odontoblasts and nonodontoblasts pulp cells. The Kruskal-Wallis/Dunn's test (scores or quantitative data) and the chi-squared test (categorical data) were used (GraphPad Prism 5.0, P < 0.05).

RESULTS

There was no differences in the number of animals exhibiting dilated/ectasic blood vessels (P = 0.242) and inflammatory cells (P = 0.489) or in the number of mast cells (P = 1.000). However, there was an increase in mononuclear CD68-positive cells (P = 0.026), immunostaining of TNF-α (P = 0.020), IL-1β (P = 0.027) and iNOS (P = 0.001) in odontoblasts, and IL-1β (P = 0.013) in nonodontoblast pulp cells dose-dependently. NFkB (nucleus and cytoplasm) and IL-18 bp did not differ between groups.

CONCLUSION

ZA modified the immune cell profile in the dental pulp, increasing the number of macrophages and expression of pro-inflammatory markers independent of NFkB.

Design and Biological Evaluation of Delivery Systems Containing Bisphosphonates

Bisphosphonates have found application in the treatment of reoccurrence of bone diseases, breast cancer, etc. They have also been found to exhibit antimicrobial, anticancer and antimalarial activities. However, they suffer from pharmacological deficiencies such as toxicity, poor bioavailability and low intestinal adsorption. These shortcomings have resulted in several researchers developing delivery systems that can enhance their overall therapeutic effectiveness. This review provides a detailed overview of the published studies on delivery systems designed for the delivery of bisphosphonates and the corresponding in vitro/in vivo results.

Effect of low-level laser therapy on bisphosphonate-treated osteoblasts

BACKGROUND

This study investigates the effect of alendronate-treated osteoblasts, as well as the effect of low-level laser therapy (LLLT) on the alendronate-treated osteoblasts. Bisphosphonate decreases the osteoblastic activity. Various treatment modalities are used to enhance the bisphosphonate-treated osteoblasts; however, there were no cell culture studies conducted using a low-level laser.

METHODS

Human fetal osteoblastic (hFOB 1.19) cells were treated with 50 μM alendronate. Then, they were irradiated with a 1.2 J/cm2 low-level Ga-Al-As laser (λ = 808 ± 3 nm, 80 mW, and 80 mA; spot size, 1 cm2; NDLux, Seoul, Korea). The cell survivability was measured with the MTT assay. The three cytokines of osteoblasts, receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), and macrophage colony-stimulating factor (M-CSF) were analyzed.

RESULTS

In the cells treated with alendronate at concentrations of 50 μM and higher, cell survivability significantly decreased after 48 h (p < 0.05). After the applications of low-level laser on alendronate-treated cells, cell survivability significantly increased at 72 h (p < 0.05). The expressions of OPG, RANKL, and M-CSF have decreased via the alendronate. The RANKL and M-CSF expressions have increased, but the OPG was not significantly affected by the LLLT.

CONCLUSIONS

The LLLT does not affect the OPG expression in the hFOB cell line, but it may increase the RANKL and M-CSF expressions, thereby resulting in positive effects on osteoclastogenesis and bone remodeling.

Effect of Clodronate on Antigenic Profile, Growth, and Differentiation of Osteoblast-Like Cells

PURPOSE

To evaluate the role of osteoblasts in bisphosphonate-related osteonecrosis of the jaw (BRONJ) by studying the effects of different concentrations of clodronate, a non-nitrogen-containing bisphosphonate, on osteoblast growth, differentiation, and antigenic profile.

MATERIALS AND METHODS

Osteoblast-like cells (MG63) were incubated in culture medium with different doses of clodronate. Their proliferative capacity was determined with a spectrophotometric technique (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium assay). Flow cytometry was used to study the antigenic profile. Cell differentiation was evaluated by nodule formation and alkaline phosphatase (ALP) activity was measured by spectrophotometric assay.

RESULTS

Clodronate had a significant stimulatory effect on osteoblast-like cell (MG63) proliferation (P < .05). A significant decrease in the expression of CD54, CD80, CD86, and HLA-DR membrane antigens versus controls was observed after 24 hours of treatment with the different clodronate doses assayed (P < .05). A significant decrease (P = .004) in ALP activity was found after 24 hours of treatment with the lowest dose (10(-9) mol/L), and a significant decrease in calcium deposition was found after 15 and 21 days of treatment (P < .05).

CONCLUSION

Clodronate increases the proliferation of MG63 osteoblast-like cells and decreases their differentiation capacity, generally at low doses, and modulates the expression of costimulatory molecules associated with immune function. Clodronate exerts its effect on osteoblasts by altering their physiology and impairing their repair capacity, which could be related to the development of BRONJ. However, further research is warranted to elucidate fully the mechanisms by which bisphosphonates can produce this disease.

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.

Combined effect of bisphosphonate and recombinant human bone morphogenetic protein 2 on bone healing of rat calvarial defects

Background

This study aimed to investigate new bone formation using recombinant human bone morphogenetic protein 2 (rhBMP-2) and locally applied bisphosphonate in rat calvarial defects.

Methods

Thirty-six rats were studied. Two circular 5 mm diameter bony defect were formed in the calvaria using a trephine bur. The bony defect were grafted with Bio-Oss® only (group 1, n = 9), Bio-Oss® wetted with rhBMP-2 (group 2, n = 9), Bio-Oss® wetted with rhBMP-2 and 1 mM alendronate (group 3, n = 9) and Bio-Oss® wetted with rhBMP-2 and 10 mM alendronate (group 4, n = 9). In each group, three animals were euthanized at 2, 4 and 8 weeks after surgery, respectively. The specimens were then analyzed by histology, histomorphometry and immunohistochemistry analysis.

Results

There were significant decrease of bone formation area (p < 0.05) between group 4 and group 2, 3. Group 3 showed increase of new bone formation compared to group 2. In immunohistochemistry, collagen type I and osteoprotegerin (OPG) didn’t show any difference. However, receptor activator of nuclear factor κB ligand (RANKL) decreased with time dependent except group 4.

Conclusion

Low concentration bisphosphonate and rhBMP-2 have synergic effect on bone regeneration and this is result from the decreased activity of RANKL of osteoblast.

Effects of alendronate on osteoclast formation and activity in vitro

INTRODUCTION

Root resorption is a common complication after replantation following traumatic dental avulsion. Endodontic therapy combined with local and intracanal medications aims to avoid osteoclastic activity. In such cases, the application of alendronate (ALN), a bisphosphonate widely used for the treatment of bone disorders, could be of clinical relevance. This study evaluated alendronate biocompatibility on periodontal ligament cells as well as its effects on an in vitro osteoclastogenesis model.

METHODS

Alendronate cytotoxicity (10(-3) to 10(-9) mol/L) in human periodontal ligament fibroblasts, human osteogenic sarcoma cells, and murine osteoclastic precursors (RAW 264.7) was analyzed using cell number determination, cell viability, and proliferation assays. ALN (10(-6) to 10(-12) mol/L) effects on RANKL-induced osteoclastogenesis of RAW cells were assessed by tartrate-resistant acid phosphatase (TRAP) staining and activity and real-time polymerase chain reaction.

RESULTS

ALN at higher concentrations was cytotoxic for all cell types, inhibiting significantly the proliferation of human osteogenic sarcoma cells and human periodontal ligament fibroblasts (≥10(-5) mol/L). TRAP activity and expression of the osteoclast markers TRAP and cathepsin K by RAW-derived osteoclasts decreased significantly with ALN at low concentrations, reaching the maximum effect at 10(-10) mol/L.

CONCLUSIONS

We showed that ALN at very low concentrations is an effective inhibitor of RANKL-generated osteoclasts, without causing cytotoxic effects on their precursors or periapical cells. ALN at such concentrations might be useful to prevent replacement resorption in avulsed teeth.

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.

Effects of zoledronic acid on physiologic bone remodeling of condylar part of TMJ: a radiologic and histomorphometric examination in rabbits

Objective. The purpose of the present study is to evaluate the effects of systemically administered zoledronic acid (ZA) on the physiological bone remodeling and the microarchitectural parameters of the condylar part of TMJ in a rabbit model. Study Design. Thirty skeletally mature male New Zealand white rabbits were randomly divided into two groups. The experimental group was administered an intravenous, single dose of 0.1 mg/kg ZA diluted with 15 mL of saline in a 15-minute perfusion with an infusion pump. The control group was administered only saline infusion for 15 minutes. All rabbits were sacrificed on the 21st postoperative day. Radiodensitometric and histomorphometric examinations were performed on the harvested mandibular condyles. The data were analyzed statistically. Results. Radiodensitometric findings showed that ZA treatment resulted in a significant increase in the mineralization of mandibular condyle. This result was supported by the histomorphometric findings. Conclusion. The present study has revealed that a temporary delay in the physiological bone remodeling using single dose of ZA increases bone mineral content and makes the microarchitecture of the mandibular condyle more compact. These effects may be regarded as base data and considered in numerous clinical situations including TMJ.

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.

Healing of the bone with anti-fracture drugs

INTRODUCTION

Fracture healing is a complex process that leads to the restoration of tissue integrity through bone repair and represents a unique physiological characteristic of bone. Developing a better understanding of a fracture is essential to plan best noninvasive treatment for the patient. In osteoporosis, the patient who suffers of a fragility fracture is recommended to initiate a treatment with compounds active in preventing other low-energy skeletal trauma. Pharmaceutical industries are developing controlled clinical trials aiming to evaluate the capability of osteoporosis drugs to accelerate fracture healing.

AREAS COVERED

In preparing this review, a search was made with key words encompassing 'osteoporosis anti-fracture drugs and bone repair/healing', 'antiresorptives and bone repair/healing', 'bone-forming agents and bone repair/healing', and 'osteoporosis/anti-fracture drugs in fractures'. The results published in the area of the use of registered anti-fracture drugs to improve fracture repair and the efforts made to recommend measures for clinical outcomes in fracture healing acceleration are described in this report.

EXPERT OPINION

At present, the use of systemic pharmacological agents active to improve fracture healing by the clinicians is controversial and clinicians and scientists must do a better job in determining the methods of assessment for fracture healing.

Low concentrations of zoledronic acid are better at regulating bone formation and repair

The purpose of this study was to investigate optimal concentrations of zoledronic acid (ZA) in terms of their effect on the proliferation, differentiation, and mineralization of primary osteoblasts (OBs) and fibroblasts (FBs). Primary OBs and FBs isolated from patients with clinical osteogenesis imperfecta (OI) and developmental dysplasia of the hip (DDH) were treated in vitro with serial concentrations of ZA ranging from 10(-3) M to 10(-13) M. An MTT ((3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)) colorimetric assay, flow cytometry, alkaline phosphatase (ALP) determination activity, and alizarin red staining were used to measure the proliferation, differentiation, and mineralization of cells. The MTT assay indicated that high concentrations of ZA may be toxic to cultured cells. No obvious inhibition was observed with a ZA concentration of 10(-7) M to 10(-10) M. Proliferation was evident with a ZA concentration below 10(-11) M (p < 0.05). Flow cytometry analysis revealed that cell cycle was arrested at G1/G0 stage with a ZA concentration ranging from 10(-10) M to 10(-8) M. ZA did not enhance ALP activity at a concentration of 10(-8) M or 10(-10) M. Alizarin red staining indicated the mineralization of primary OBs with a low concentration of ZA (10(-12) M). In conclusion, this in vitro study indicated that ZA-mediated cell proliferation was dose-dependent and that ZA did not inhibit cell proliferation at concentrations below 10(-8) M. These findings suggest low concentrations of ZA have more of an effect on cell differentiation and mineralization, so low concentrations are better at regulating bone formation and repair.

Comparison of effects of clodronate and zoledronic acid on the repair of maxilla surgical wounds - histomorphometric, receptor activator of nuclear factor-kB ligand, osteoprotegerin, von Willebrand factor, and caspase-3 evaluation

BACKGROUND

The aim of this study was to compare clodronate and zoledronic acid regarding their influence on the repair of surgical wounds in maxillae (soft tissue wound and tooth extraction) and their relation to osteonecrosis.

MATERIAL AND METHODS

Thirty-four Wistar rats were allocated into three groups according to the treatment received: (i) 12 animals treated with zoledronic acid, (ii) 12 animals treated with clodronate and (iii) 10 animals that were given saline solution. All animals were subjected to tooth extractions and surgically induced soft tissue injury. Histological analysis of the wound sites was performed by means of hematoxylin-eosin (H&E) staining and immunohistochemical staining for receptor activator of nuclear factor-kB ligand (RANKL), osteoprotegerin (OPG), von Willebrand factor, and caspase-3.

RESULTS

The zoledronic acid group showed higher incidence of non-vital bone than did the clodronate group at the tooth extraction site. At the soft tissue wound site, there were no significant differences in non-vital bone between the test groups. RANKL, OPG, von Willebrand factor, and caspase-3 did not show significant differences between the groups for both sites of surgical procedures.

CONCLUSION

Both of the bisphosphonates zoledronic acid and clodronate are capable of inducing maxillary osteonecrosis. Immunohistochemical analysis suggests that the involvement of soft tissues as the initiator of osteonecrosis development is less probable than has been pointed out.

Biomimetic coating of bisphosphonate incorporated CDHA on Ti6Al4V

Bi-functional coatings of carbonated calcium deficient hydroxyapatite (CDHA) on Ti alloys were developed by using a biomimetic coating process. The bi-functionality was achieved by loading alendonate sodium (AS), an approved bisphosphonate drug used for the treatment of osteoporosis, into the inner layers of CDHA coatings. Three possible methods of loading AS into CDHA coatings were systematically studied and compared. The results indicated that the co-precipitation method had greater benefits and can modify the release profile of AS by incorporating AS in the inner layers of the coatings. As a preliminary study, the influences of applied AS dosage to CDHA coatings were evaluated using XRD and SEM. In vitro tests indicated that the AS content on CDHA coatings played a significant role, and optimum AS content in local area is beneficial for osteoblast cells proliferation. It is expected that the CDHA-AS coatings via the co-precipitation approach have potential for bone tissue engineering applications.

BISPHOSPHONATE-INDUCED MAXILLOFACIAL OSTEONECROSIS IN OSTEOPOROTIC INDIVIDUALS

Bisphosphonate-related osteonecrosis of the maxillae may be an important complication of long-term osteoporosis treatment. The possibility of osteonecrosis of the maxillae in patients exposed to nitrogenated bisphosphonates was first described in 2003. Since then, case reports and retrospective studies have demonstrated higher percentages of occurrence of osteonecrosis in patients who have used or are using bisphosphonates. Although this complication may be spontaneous, invasive oral procedures have a role as risk factors associated with dental procedures such as tooth extractions and other bone operations. In addition, tooth infections and periodontal disease have been reported to be the main risk factors for development of bisphosphonate-induced osteonecrosis of the maxillae. For this reason, dentists, general clinicians, orthopedists, geriatricians and oral-maxillofacial surgeons need to be aware of this problem and work in a multidisciplinary environment, thereby stimulating early diagnosis and prevention of further potential cases.

Osteonecrosis of the posterior mandible after implant insertion: a clinical and histological case report

BACKGROUND

In the past few years, the occurrence of an oral lesion, called osteonecrosis of the jaw (ONJ), has been increasingly reported in patients undergoing treatment with bisphosphonates (BPs); however, few published histological studies of ONJ can be found in the literature.

PURPOSE

The aim of the present case was to report an occurrence of ONJ after implant insertion.

MATERIALS AND METHODS

Multiple myeloma was diagnosed to a 65-year-old female. After 5 years of treatment with intravenous clodronate, two dental implants were inserted in the mandibular molar region. No preexisting bone lesions were present at a preoperative panoramic radiography. Before implant insertion, the patient had suspended the treatment with clodronate for 3 months. Four months after the implant insertion, a breakdown of the oral mucosa covering the implants occurred with a purulent discharge; periapical radiolucency was present around both implants. An en-block resection on the alveolar bone including the two implants was performed. No signs of recurrence of the lesion were observed after a follow-up of 20 months.

RESULTS

At the interface of one of the implants, a gap was observed between bone and implant. This bone was nonvital, and many osteocyte lacunae were empty. Moreover, this bone appeared to be partially demineralised. No newly formed bone or osteoblasts were present. Bone trabeculae were observed, on the other hand, within the apical implant threads of the other implant. A close connection was observed between this bone and the implant surface.

DISCUSSION

The histological findings showed some areas with osseointegration in patients undergoing BP treatment for malignant disease; however, any invasive procedure can determine the onset of osteonecrosis.

CONCLUSION

In conclusion, there is certainly a temporal association between BP use and development of ONJ, but a correlation does not necessarily mean causation. Moreover, generalizations about this complex relationship cannot be made on the basis of a single case report. In patients undergoing intravenous treatment, clinicians must be aware of the increased risk of implant failure and, probably, implant insertion should be avoided at all until more conclusive data are available.

Bisphosphonates inhibit phosphorylation of signal transducer and activator of transcription 3 and expression of suppressor of cytokine signaling 3: implications for their effects on innate immune function and osteoclastogenesis

OBJECTIVE

This study tested the effects of bisphosphonates (BPs) on the suppressor of cytokine signaling 3 (SOCS3) protein in macrophages. SOCS3 has been shown to regulate cell differentiation and survival; however, its potential role in mediating the effects of BPs has not been explored.

STUDY DESIGN

The cell viability of murine RAW 267.4 macrophages was assessed after culturing with control medium or media containing increasing concentrations of 2 BPs (ibandronate or clodronate) for 24, 48, and 72 hours. The phosphorylation status of signal transducer and activator of transcription 3 (STAT3) and the expression of SOCS3 protein levels were determined by Western blot analysis.

RESULTS

In control cultures, STAT3 phosphorylation and STAT3 and SOCS3 protein levels increased within 5 minutes after the addition of fresh medium. This increase was inhibited in cultures treated with both BPs. Macrophage cell viability also decreased after BP treatment.

CONCLUSIONS

These data demonstrate that, in addition to their effects on macrophage viability, BPs can decrease STAT3 and SOCS3 expression, which are important modulators of immune responses and bone homeostasis.

Bisphosphonates and pathologic complete response to taxane- and anthracycline-based neoadjuvant chemotherapy in patients with breast cancer

BACKGROUND

Several studies have suggested that bisphosphonates have an antitumor effect. In the current study, the authors sought to evaluate whether the use of bisphosphonates increased the rate of pathological complete response (pCR) in patients with breast cancer.

METHODS

The authors identified 1449 patients with breast cancer who were receiving taxane- and anthracycline-based neoadjuvant chemotherapy between 1995 and 2007 at The University of Texas MD Anderson Cancer Center. Patients who received bisphosphonates for osteopenia or osteoporosis while receiving chemotherapy were also identified. The primary outcome was the percentage of patients achieving a pCR. Groups were compared using the chi-square test. A multivariable logistic regression model was fit to examine the relation between the use of bisphosphonates and pCR. An exploratory survival analysis using the Kaplan-Meier method was performed; groups were compared using the log-rank test.

RESULTS

Of the 1449 patients included, 39 (2.7%) received bisphosphonates. Those receiving bisphosphonates were older (P < .001) and less likely to be obese (P = .04). The pCR rate was 25.4% in the bisphosphonate group and 16% in the nonbisphosphonate group (P = .11). In the multivariable model, patients treated with bisphosphonates tended to have higher rates of pCR (odds ratio, 2.18; 95% confidence interval, 0.90-5.24); however, the difference was not found to be statistically significant. With a median follow-up of 55 months (range, 3 months-145 months), no differences in disease recurrence or survival were observed.

CONCLUSIONS

The use of bisphosphonates at the time of neoadjuvant chemotherapy was not found to be associated with a statistically significant increase in the rates of pCR. The observed estimates suggest a positive effect; however, the small percentage of patients receiving bisphosphonates likely affected the power to detect a statistically significant difference.

Pamidronate, farnesyl transferase, and geranylgeranyl transferase-I inhibitors affects cell proliferation, apoptosis, and OPG/RANKL mRNA expression in stromal cells of giant cell tumor of bone

Giant cell tumor (GCT) is the most common nonmalignant primary bone tumor reported in Hong Kong. It usually affects young adults between the ages of 20 and 40. This tumor is well known for its potential to recur following treatment. To date no effective adjuvant therapy exists for GCT. Our project aimed to study the effects of pamidronate (PAM), farnesyl transferase inhibitor (FTI-277), geranylgeranyl transferase inhibitor (GGTI-298), and their combinations on GCT stromal cells (SC). Individual treatment with PAM, FTI-277, and GGTI-298, inhibited the cell viability and proliferation of GCT SC in a dose-dependent way. Combination of FTI-277 with GGTI-298 caused synergistic effects in reducing cell viability, and its combination index was 0.49, indicating a strong synergism. Moreover, the combination of FTI-277 with GGTI-298 synergistically enhanced cell apoptosis and activated caspase-3/7, -8, and -9 activities. PAM induced cell-cycle arrest at the S-phase. The combination of PAM with GGTI-298 significantly increased OPG/RANKL mRNA ratio and activated caspase-3/7 activity. Our findings support that the combination of bisphosphonates with GGTIs or FTIs with GGTIs may be used as potential adjuvants in the treatment of GCT of bone.

Effects of zoledronic acid on healing of mandibular fractures: an experimental study in rabbits

PURPOSE

The purpose of the present study was to evaluate the effects of systemically administered zoledronic acid (ZA) on mandibular fracture healing in a rabbit model using radiodensitometric, biomechanical, histologic, and histomorphometric methods.

MATERIALS AND METHODS

A total of 36 skeletally mature male New Zealand white rabbits were used. The rabbits were randomly divided into 2 groups. A mandibular corpus fracture was created experimentally in all 36 rabbits. The experimental group was administered an intravenous, single dose of 0.1 mg/kg ZA, and the control group was administered only saline infusion during the procedure. All rabbits were sacrificed on the 21st postoperative day. Digital radiodensitometric analysis, a 3-point bending test, and histologic and histomorphometric examinations were performed on the harvested hemimandibles. The data were analyzed statistically.

RESULTS

Biomechanical testing data showed that ZA treatment resulted in a significant increase in the healed bone strength. This result was supported by the radiologic, histologic, and histomorphometric findings.

CONCLUSIONS

The results of the present study have revealed that systemic administration of ZA accelerates and improves the bone healing of mandibular fractures.

Small interfering RNA knocks down the molecular target of alendronate, farnesyl pyrophosphate synthase, in osteoclast and osteoblast cultures

Farnesyl pyrophosphate synthase (FPPS), an enzyme in the mevalonate pathway, is the inhibition target of alendronate, a potent FDA-approved nitrogen-containing bisphosphonate (N-BP) drug, at the molecular level. Alendronate not only inhibits osteoclasts but also has been reported to positively affect osteoblasts. This study assesses the knockdown effects of siRNA targeting FPPS compared with alendronate in both osteoclast and osteoblast cultures. Primary murine bone marrow cell-induced osteoclasts and the preosteoblast MC3T3-E1 cell line were used to assess effects of anti-FPPS siRNA compared with alendronate. Results show that both FPPS mRNA message and protein knockdown in serum-based culture is correlated with reduced osteoclast viability. FPPS siRNA is more potent than 10 μM alendronate, but less potent than 50 μM alendronate on reducing osteoclast viability. Despite FPPS knockdown, no significant changes were observed in osteoblast proliferation. FPPS knockdown promotes osteoblast differentiation significantly but not cell mineral deposition. However, compared with 50 μM alendronate dosing, FPPS siRNA does not exhibit cytotoxic effects on osteoblasts while producing significant effects on ostoblast differentiation. Both siRNA and alendronate at tested concentrations do not have significant effects on cultured osteoblast mineralization. Overall, results indicate that siRNA against FPPS could be useful for selectively inhibiting osteoclast-mediated bone resorption and improving bone mass maintenance by influencing both osteoclasts and osteoblasts in distinct ways.

The effects of risedronate and exercise on osteoporotic lumbar rat vertebrae and their sensory innervation

STUDY DESIGN

Investigation of sensory innervation of rat osteoporotic lumbar vertebrae using in vitro and in vivo models.

OBJECTIVE

To investigate (1) sensory innervation of osteoporotic rat vertebrae, (2) effects of risedronate on sensory neurons, (3) effects of osteoporosis treatment on bone mineral densities (BMDs) and the sensory innervation.

SUMMARY OF BACKGROUND DATA

Osteoporotic patients without fractures sometimes experience vague low back pain of unknown origin. The mechanisms of osteoporosis treatments against the pain are unclear.

METHODS

(1) The expression of calcitonin gene-related peptide (CGRP) immunoreactive (-ir) or transient receptor potential vanilloid 1 (TRPV1)-ir nerve fibers in vertebrae and dorsal root ganglions (DRG) innervating L3 vertebrae of Sprague Dawley rats labeled with neurotracer were examined in control, sham, and ovariectomized (OVX) rats. (2) Cultured rat neonate DRG neurons in media containing different concentrations of risedronate were immunostained for CGRP, and we measured its activity using axonal length and proportion of CGRP-ir neurons. (3) BMDs and CGRP expression in DRG neurons innervating L3 vertebrae were examined in the following 5 groups: sham (treated with saline), OVX (saline), OVX+EXE (treadmill exercise), OVX+RIS (risedronate), and OVX+RIS+EXE (risedronate and exercise).

RESULTS

(1) A few CGRP-ir or TRPV1-ir nerve fibers were observed in the bone marrow. CGRP or TRPV1 expression in DRG was elevated in the OVX group (P < 0.05). (2) The axonal length and proportion of CGRP-ir neurons were dose-dependently suppressed (P < 0.05). (3) BMDs improved and the CGRP expression decreased in the risedronate-treated groups (P < 0.05), especially in the OVX+RIS+EXE group.

CONCLUSION

Sensory innervation of osteoporotic rat vertebrae showed increased expression of CGRP and TRPV1 in DRG neurons. Risedronate suppressed activity of CGRP-ir neurons in vitro, improved BMD, and decreased CGRP expression, especially together with exercise in vivo.

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.

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.