Compactin suppresses bone resorption by inhibiting the fusion of prefusion osteoclasts and disrupting the actin ring in osteoclasts

β-Caryophyllene and Statins in Bone Fracture Healing - A Narrative Review

Bone fractures are a leading cause of morbidity and healthcare expenditure globally. The complex healing process involves inflammation, cartilage formation, mineralization, and bone remodeling. Current treatments like immobilization, surgery, and bone grafting, though effective, pose significant challenges, such as prolonged recovery and high costs. Emerging therapies such as biological agents, pharmacological treatments, and physical stimulation techniques are also associated with high costs, side effects, and practical applicability limitations. There is a critical need for alternative therapies that are cost-effective, safe, and easy to use. Recent studies suggest the potential of β-caryophyllene (BCP) and statins in promoting bone healing. BCP, a naturally occurring anti-inflammatory and antioxidant compound found in essential oils, enhances osteoblast activity and inhibits osteoclastogenesis. Statins, known for their cholesterol-lowering effects, also promote bone formation and reduce bone resorption through multiple biochemical pathways. Both BCP and statins have shown promising results in preclinical studies, enhancing bone density and promoting fracture healing. This review explores the individual and potential synergistic effects of BCP and statins on bone fracture healing. It highlights the complementary mechanisms of these agents: BCP's anti-inflammatory and osteogenic properties and statins' ability to inhibit osteoclast activity and promote angiogenesis. Combining BCP and statins could offer a multifaceted approach to enhance fracture healing, reduce complications, and improve patient outcomes. While individual effects are supported preclinically, further studies investigating synergies, formulations, and clinical translation are needed to develop this promising novel therapeutic approach for improving fracture repair outcomes.

Preoperative Statin Exposure Reduces Periprosthetic Fractures and Revisions following Total Knee Arthroplasty

The purpose of this study is to examine patients undergoing primary total knee arthroplasty (TKA) with and without prior history of statin use. We specifically evaluated (1) 90-day to 2-year periprosthetic fractures, (2) revisions, and (3) respective risk factors. We queried a national, all-payer database for patients undergoing primary TKA between 2010 and 2020. Chronic statin exposure was then identified and defined as more than three prescriptions filled within 1 year prior to TKA (statin users). A control cohort of patients undergoing TKA without the prior history of statin use was then created (statin naïve). Cohorts were matched 1:1 based on age range, Charlson Comorbidity Index, sex, diabetes, obesity, and tobacco use, yielding 579,136 patients. Multivariate logistic regression was performed to evaluate the risk factors for periprosthetic fractures and revisions, adjusted for demographics and comorbidities. Statin users had a lower incidence of periprosthetic fractures from 90 days to 2 years compared with the statin naïve (p < 0.001). Similarly, statin users had a lower incidence of revisions at 90 days to 2 years (p < 0.001). Using the statin-naïve cohort as a reference, statin use was independently associated with decreased odds of periprosthetic fractures and revisions. Statin use was associated with a reduced risk of periprosthetic fractures and revisions. These results may mitigate postoperative risks though statin therapy is currently not recommended for fracture-related benefits alone.

Simvastatin therapy in higher dosages deteriorates bone quality: Consistent evidence from population-wide patient data and interventional mouse studies

BACKGROUND

Combining mouse experiments with big data analysis of the Austrian population, we investigated the association between high-dose statin treatment and bone quality.

METHODS

The bone microarchitecture of the femur and vertebral body L4 was measured in male and ovariectomized female mice on a high-fat diet containing simvastatin (1.2 g/kg). A sex-specific matched big data analysis of Austrian health insurance claims using multiple logistic regression models was conducted (simvastatin 60-80 mg/day vs. controls; males: n = 138,666; females: n = 155,055).

RESULTS

High-dose simvastatin impaired bone quality in male and ovariectomized mice. In the trabecular femur, simvastatin reduced bone volume (µm³: ♂, 213 ± 15 vs. 131 ± 7, p < 0.0001; ♀, 66 ± 7 vs. 44 ± 5, p = 0.02) and trabecular number (1/mm: ♂, 1.88 ± 0.09 vs. 1.27 ± 0.06, p < 0.0001; ♀, 0.60 ± 0.05 vs. 0.43 ± 0.04, p = 0.01). In the cortical femur, bone volume (mm³: ♂, 1.44 ± 0.03 vs. 1.34 ± 0.03, p = 0.009; ♀, 1.33 ± 0.03 vs. 1.12 ± 0.03, p = 0.0002) and cortical thickness were impaired (µm: ♂, 211 ± 4 vs. 189 ± 4, p = 0.0004; ♀, 193 ± 3 vs. 169 ± 3, p < 0.0001). Similar impairments were found in vertebral body L4. Simvastatin-induced changes in weight or glucose metabolism were excluded as mediators of deteriorations in bone quality. Results from mice were supported by a matched cohort analysis showing an association between high-dose simvastatin and increased risk of osteoporosis in patients (♂, OR: 5.91, CI: 3.17-10.99, p < 0.001; ♀, OR: 4.16, CI: 2.92-5.92, p < 0.001).

CONCLUSION

High-dose simvastatin dramatically reduces bone quality in obese male and ovariectomized female mice, suggesting that direct drug action accounts for the association between high dosage and increased risk of osteoporosis as observed in comparable human cohorts. The underlying pathophysiological mechanisms behind this relationship are presently unknown and require further investigation.

IFN-β mediates the anti-osteoclastic effect of bisphosphonates and dexamethasone

Zoledronic acid (Zol) is a potent bisphosphonate that inhibits the differentiation of monocytes into osteoclasts. It is often used in combination with dexamethasone (Dex), a glucocorticoid that promotes the resolution of inflammation, to treat malignant diseases, such as multiple myeloma. This treatment can result in bone pathologies, namely medication related osteonecrosis of the jaw, with a poor understanding of the molecular mechanism on monocyte differentiation. IFN-β is a pro-resolving cytokine well-known as an osteoclast differentiation inhibitor. Here, we explored whether Zol and/or Dex regulate macrophage osteoclastic differentiation via IFN-β. RAW 264.7 and peritoneal macrophages were treated with Zol and/or Dex for 4-24 h, and IFN-β secretion was examined by ELISA, while the IFN stimulated gene (ISG) 15 expression was evaluated by Western blotting. RANKL-induced osteoclastogenesis of RAW 264.7 cells was determined by TRAP staining following treatment with Zol+Dex or IFN-β and anti-IFN-β antibodies. We found only the combination of Zol and Dex increased IFN-β secretion by RAW 264.7 macrophages at 4 h and, correspondingly, ISG15 expression in these cells at 24 h. Moreover, Zol+Dex blocked osteoclast differentiation to a similar extent as recombinant IFN-β. Neutralizing anti-IFN-β antibodies reversed the effect of Zol+Dex on ISG15 expression and partially recovered osteoclastic differentiation induced by each drug alone or in combination. Finally, we found Zol+Dex also induced IFN-β expression in peritoneal resolution phase macrophages, suggesting these drugs might be used to enhance the resolution of acute inflammation. Altogether, our findings suggest Zol+Dex block the differentiation of osteoclasts through the expression of IFN-β. Revealing the molecular pathway behind this regulation may lead to the development of IFN-β-based therapy to inhibit osteoclastogenesis in multiple myeloma patients.

Effects of Atorvastatin on Periodontitis of Rats Subjected to Glucocorticoid-Induced Osteoporosis

BACKGROUND

Atorvastatin (ATV) has shown pleiotropic effects on bone tissue, and osteoporosis can aggravate periodontitis. Thus, the effects of ATV on experimental periodontitis (EP) in rats subjected to glucocorticoid-induced osteoporosis (GIOP) was assessed.

METHODS

Male Wistar rats were divided into the following groups: 1) naive; 2) EP; 3) GIOP + EP; and 4) ATV. Groups GIOP + EP and ATV received 7 mg/kg dexamethasone intramuscularly once per week for 5 weeks, and the others received saline (SAL). Groups EP, GIOP + EP, and ATV were submitted to EP by ligature around the maxillary left second molars for 11 days. Group ATV received 27 mg/kg ATV orally, and the others received SAL 30 minutes before EP. Periodontium was analyzed by macroscopy, microtomography, and histopathology; by immunohistochemical examination of receptor activator of nuclear factor-κB ligand (RANKL), osteoprotegerin (OPG), wingless (WNT) 10b, dickkopf-related protein 1 (DKK-1), and β-catenin; and by enzyme-linked immunosorbent assay analysis of myeloperoxidase (MPO), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, IL10, reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT). Leukogram, liver and kidney enzymes, and bone-specific alkaline phosphatase (BALP) serum levels were evaluated.

RESULTS

ATV decreased bone loss, reduced MPO, TNF-α, IL-1β, IL-6, and IL-8, and increased IL-10, GSH, SOD, and CAT levels. ATV reduced RANKL and DKK-1 and increased OPG, WNT10b, and β-catenin expressions and BALP activity.

CONCLUSION

ATV reduced inflammation, oxidative stress, and bone loss in rats with EP and GIOP, with participation of the WNT signaling pathway.

Simvastatin-doped pre-mixed calcium phosphate cement inhibits osteoclast differentiation and resorption

Simvastatin, a cholesterol lowering drug, has been shown to have positive effects on fracture healing and bone regeneration based on its dual effect; bone anabolic and anti-resorptive. In this study the focus has been on the anti-resorptive effect of the drug and its impact on the degradation of acidic calcium phosphate cement. The drug was added to the pre-mixed acidic cement in three different doses (0.1, 0.25 and 0.5 mg/g cement) and the release was measured. Furthermore the effect of the loaded cements on osteoclast differentiation and resorption was evaluated by TRAP activity, number of multinucleated cells, gene expression and calcium ion concentration in vitro using murine bone marrow macrophages. The simvastatin did not affect the cell proliferation while it clearly inhibited osteoclastic differentiation at all three doses as shown by TRAP staining, TRAP activity and gene expression. Consistent with these results, simvastatin also impaired resorption of cements by osteoclasts as indicated by reduced calcium ion concentrations. In conclusion, our findings suggest that simvastatin-doped pre-mixed acidic calcium phosphate cement inhibits the osteoclastic mediated resorption of the cement thus slowing down the degradation rate. In addition with simvastatin's bone anabolic effect it makes the cement-drug combination a promising bone graft material, especially useful for sites with compromised bone formation.

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.

Adseverin plays a role in osteoclast differentiation and periodontal disease-mediated bone loss

Osteoclast differentiation and function are highly dependent on the assembly and turnover of actin filaments, but little is known about the roles of actin binding proteins in these processes. Adseverin (Ads), a member of the gelsolin superfamily of actin capping and severing proteins, regulates actin filament turnover and can regulate the turnover of cortical actin filaments of chromaffin cells during exocytosis. Using a conditional Ads knockout mouse model, we confirmed our previous finding in cultured cells that Ads plays a role in osteoclastogenesis (OCG) and actin cytoskeletal organization in osteoclasts. Here we show that Ads is required for osteoclast formation and that when alveolar bone resorption is experimentally induced in mice, genetic deletion of Ads prevents osteoclast-mediated bone loss. Further, when Ads-null osteoclasts are cultured, they exhibit defective OCG, disorganized podosome-based actin filament superstructures, and decreased bone resorption. Reintroduction of Ads into Ads-null osteoclast precursor cells restored these osteoclast defects. Collectively, these data demonstrate a unique and osteoclast-specific role for Ads in OCG and osteoclast function.

Influence of vitamin D status on the effect of statins on bone mineral density and bone turnover markers in postmenopausal women

OBJECTIVE

This study sought to assess whether the association between statin use and bone mineral density (BMD) and bone turnover markers is modulated by serum 25-hydroxyvitamin D (25OHD) levels in postmenopausal women. Design, Participants, and Settings: Approximately 1422 postmenopausal women were recruited from the Camargo Cohort after excluding those with any known medical disorder or drug that might affect bone metabolism. Participants were categorized into four groups: 25OHD levels of 20 ng/mL or less and not taking statins (group 1; n = 492); 25OHD levels greater than 20 ng/mL and on statins (group 2; n = 143); 25OHD levels of 20 ng/mL or less and using statins (group 3; n = 112); and 2OHD levels greater than 20 ng/mL and non-statin use (group 4; n = 675). Multivariate analyses were performed to compare BMD and bone turnover markers between groups.

RESULTS

Women in group 2 had an adjusted femoral neck and total hip BMD higher than women in group 1 (P < .0001 and P = .003, respectively). A trend toward a significant difference was observed regarding lumbar BMD (P = .08). Serum aminoterminal propeptide of type 1 collagen and C-terminal telopeptide of type 1 collagen levels were lower in group 2 than in group 1, in crude and adjusted models, although only serum C-terminal telopeptide of type 1 collagen difference was significant (P = .009).

CONCLUSIONS

Women on statins and serum 25OHD levels above 20 ng/mL have greater BMD and less bone resorption than those without either of the factors. Differences, however, are not significant in women with only one of them. Vitamin D and statins seem to interact positively in their effects on bone metabolism.

Statins, bone metabolism and treatment of bone catabolic diseases

The discovery that statins had bone anabolic properties initiated many investigations into their use for treatment of bone catabolic diseases, such as osteoporosis. This paper reviews the molecular basis of statin's role in bone metabolism, and animal and human studies on the impact of systemic statins on osteoporosis-induced bone fracture incidence and healing, and on bone density. Limitations of systemic statins are described along with alternative dosing strategies, including local applications and bone-targeting systemic preparations. The principal findings of this review are: (1) traditional oral dosing with statins results in minimal efficacy in the treatment of osteoporosis; (2) local applications of statins show promise in the treatment of accessible bony defects, such as periodontitis; and (3) systemically administered statins which can target bone or inflammation near bone may be the safest and most effective strategy in the treatment of osseous deficiencies.

Stimulation of osteoclast formation by RANKL requires interferon regulatory factor-4 and is inhibited by simvastatin in a mouse model of bone loss

Diseases of bone loss are a major public health problem. Here, we report the novel therapeutic action of simvastatin in osteoclastogenesis and osteoprotection, demonstrated by the ability of simvastatin to suppress osteoclast formation in vitro and in vivo. We found that in vitro, IRF4 expression is upregulated during osteoclast differentiation induced by RANKL (receptor activator of nuclear factor-κB ligand), while simvastatin blocks RANKL-induced osteoclastogenesis and decreases expression of NFATc1 (nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1), IRF4 and osteoclast markers. We also show that IRF4 acts in cooperation with NFATc2 and NF-κB on the promoter region of NFATc1 to accelerate its initial transcription during the early stage of osteoclastogenesis. Moreover, our study using IRF4 siRNA knockdown directly demonstrates the requirement for IRF4 in NFATc1 mRNA transcription and its necessity in RANKL-induced osteoclast differentiation. Our results suggest that the reduction in osteoclastogenesis is partly due to the inhibition of IRF4 production in RANKL-induced osteoclast differentiation. To investigate the in vivo effects of simvastatin in RANKL-treated mice, we examined the bone mineral density (BMD) of a mouse model of bone loss, and found that simvastatin significantly reduced bone loss by suppressing osteoclast numbers in vivo, even in the presence of high concentrations of RANKL. These results suggest that the depletion of osteoclasts is not due to the reduction in RANKL produced by osteoblasts in vivo. The results are consistent with the hypothesis that simvastatin blocks RANKL-induced IRF4 expression in osteoclastogenesis. We propose that the expression of IRF4 by osteoclasts could be a promising new therapeutic target in bone-loss diseases.

Mechanisms of bone anabolism regulated by statins

Osteoporosis is a common disease in the elderly population. The progress of this disease results in the reduction of bone mass and can increase the incidence of fractures. Drugs presently used clinically can block the aggravation of this disease. However, these drugs cannot increase the bone mass and may result in certain side effects. Statins, also known as HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase inhibitors, have been widely prescribed for CVD (cardiovascular disease) for decades. Nonetheless, several studies have demonstrated that statins exert bone anabolic effect and may be helpful for the treatment of osteoporosis. Several experiments have analysed the mechanisms of bone anabolism regulated by statins. In the present paper, we review the mechanisms of promoting osteogenesis, suppressing osteoblast apoptosis and inhibiting osteoclastogenesis.

Bone turnover markers in statin users: a population-based analysis from the Camargo Cohort Study

OBJECTIVE

To analyze the effects of statin use on bone turnover markers (BTM), in participants from a large population-based cohort.

SUBJECTS AND METHODS

Cross-sectional study that included 2431 subjects (1401 women and 930 men) from the Camargo Cohort. We analyzed the differences in serum BTM between statin or non-statin users, by means of a generalized linear model, adjusted for a wide set of covariates and stratified by diabetes status. We also studied the effect of the type of statin, dose, pharmacokinetic properties, and length of treatment, on BTM.

RESULTS

Five hundred subjects (21%) were taking statins (273 women and 227 men). Overall, they had lower levels of aminoterminal propeptide of type I collagen (PINP) and C-terminal telopeptide of type I collagen (CTX) than non-users (p<0.0001). BTM levels were significantly lower in diabetic women using statins, than in female non-statin users with diabetes. In men, we found similar results, but only for CTX. All the statins users had lower levels of BTM than non-users, except subjects taking fluvastatin that showed slightly higher values. In the whole sample, no differences between dose or drug-potency were noted regarding BTM. When comparing with non-statin users, only subjects taking lipophilic statins had lower BTM levels (p<0.0001). Serum CTX levels were lower in women using statins for more than 3 vs. 1-3 years (p=0.006).

CONCLUSIONS

In a large population-based cohort, serum BTM were lower in participants taking statins than in non-users, and this effect was modulated by diabetes status. Overall, this decrease in BTM was more evident in subjects receiving the more lipophilic statins, especially when using for more than 3 years.

Bisphosphonate- and statin-induced enhancement of OPG expression and inhibition of CD9, M-CSF, and RANKL expressions via inhibition of the Ras/MEK/ERK pathway and activation of p38MAPK in mouse bone marrow stromal cell line ST2

Osteoclast differentiation is influenced by receptor activator of the NF-κB ligand (RANKL), macrophage colony-stimulating factor (M-CSF), and CD9, which are expressed on bone marrow stromal cells and osteoblasts. In addition, osteoprotegerin (OPG) is known as an osteoclastogenesis inhibitory factor. In this study, we investigated whether bisphosphonates and statins increase OPG expression and inhibit the expression of CD9, M-CSF, and RANKL in the bone marrow-derived stromal cell line ST2. We found that bisphosphonates and statins enhanced OPG mRNA expression and inhibited the expression of CD9, M-CSF, and RANKL mRNA. Futhermore, bisphosphonates and statins decreased the membrane localization of Ras and phosphorylated ERK1/2, and activated the p38MAPK. This indicates that bisphosphonates and statins enhanced OPG expression, and inhibited the expression of CD9, M-CSF, and RANKL through blocking the Ras/ERK pathway and activating p38MAPK. Accordingly, we believe that its clinical applications will be investigated in the future for the development of osteoporosis therapy.

Heart drugs that affect bone

There have been important developments in our understanding of the mechanisms underlying the development of osteoporosis, and several of these mechanisms also underlie atherosclerosis. Drugs given to treat cardiovascular disease may impact on bone health in either a beneficial or a harmful way. There is evidence that nitrates are beneficial to bone, but evidence for the benefit of statins, thiazide diuretics, and β-blockers is weaker. By contrast, it is likely to be that some drugs such as loop-acting diuretics are harmful to bone, whereas evidence for harm caused by drugs such as warfarin is weaker. These observations point towards opportunities for new drug development for bone diseases, and possibly the development of treatments that will benefit more than one disease.

Statins and the joint: multiple targets for a global protection?

OBJECTIVES

Evidence exists that the pleiotropic properties of the hydroxy-methyl-glutaryl Coenzyme A reductase inhibitors (statins) are not restricted to the cardiovascular system, as they can also favorably affect the joints, with intriguing implications for the treatment of many rheumatic diseases. In the view of the increasing interest on this topic, we here review the current state of the art.

METHODS

The PubMed database was searched for articles published between 1966 and 2010 for key words referring to statins and joint diseases. All relevant English-written articles were reviewed.

RESULTS

Many pivotal studies clearly demonstrated that HMG-CoA reductase inhibitors exert a wide spectrum of beneficial effects on the 3 main compartments of the joint, ie, the synovium, the cartilage, and the subchondral bone. Such (1) anti-inflammatory, (2) immunomodulating, and (3) anabolic effects strongly support a potential role of these drugs in the treatment and/or the prevention of the most important chronic joint diseases. However, although the majority of the in vivo studies with statins on animal models of inflammatory and degenerative joint diseases showed a marked protective activity substantially confirming the in vitro experiments, data arising from clinical trials are less probative and more conflicting.

CONCLUSIONS

Statins display multiple joint-protective effects. Since oral administration of statins could result in a relatively low drug bioavailability to the joints, alternative routes of administration of the drug (transdermal, intra-articular) and/or specific delivery systems should be developed to establish the entire therapeutic potential of statins in this clinical setting.

Effects of mevastatin on grafted bone in MRL/MpJ mice

Statins, lipid-lowering drugs, have been reported to influence bone metabolism. However, the available information about their effects on bone formation and resorption in vivo is still limited. The present study was undertaken to determine whether the topical administration of mevastatin could increase the bone mass of isografted bone. The tibiae were bilaterally dissected from a donor MRL/MpJ mouse and transplanted subcutaneously in the dorsal region of a recipient mouse. One grafted tibia was topically infused for either 1, 2, 3, or 4 weeks with mevastatin, using an osmotic minipump at a dose of 2.5 pmol/hr. The other tibia was infused with 0.9% NaCl (control). Our three results were: (1) Topical mevastatin stimulated bone formation and numerous cuboidal osteoblasts appeared on the surface of newly formed bone. Bone mineral density and bone area in mevastatin-treated bone were significantly increased. (2) Topical mevastatin increased the number of osteoclasts. (3) The expression of bone morphogenetic protein-2 (BMP-2) mRNA and receptor activator of NF-kB ligand (RANKL) mRNA were upregulated in mevastatin-treated bone. These results suggest that the topical infusion of mevastatin increases bone mass of isografted bone by increasing bone turnover and, at least in part, by promoting the expression of BMP-2 and RANKL mRNA.

A phase II clinical trial does not show that high dose simvastatin has beneficial effect on markers of bone turnover in multiple myeloma

Several studies have evaluated the impact of low dose statin (20-80 mg/day) on bone metabolism with inconclusive results despite promising data of preclinical studies. In this study, we investigated the effect of high dose simvastatin (HD-Sim) on biochemical markers of bone turnover and disease activity in six heavily pretreated patients with multiple myeloma (MM). These patients were treated with simvastatin (15 mg/kg/day) for 7 days followed by a rest period of 21 days in two 4-week cycles. Endpoints were changes in the level of biochemical markers of (i) osteoclast activity (tartrate resistant acid phosphatase, TRACP); (ii) bone resorption (collagen fragments CTX and NTX); (iii) bone formation (osteocalcin and aminoterminal propeptide of type I collagen PINP); (iv) cholesterol; (v) regulators of bone metabolism [osteoprotegerin (OPG) and Dickkopf-1 (DKK-1)] and (vi) disease activity (monoclonal proteins or free light chains in serum). TRACP activity in serum and levels of collagen fragments (NTX) in urine increased for all patients temporarily during the 7 days of treatment with HD-Sim indicating that osteoclasts may have been stimulated rather than inhibited. The other markers of bone metabolism showed no change. None of the patients showed any reduction in free monoclonal light chains or monoclonal proteins in serum during treatment with HD-Sim. In spite of the fact that bone turn over effects of HD-Sim may have been blunted by concomitant treatment of patients with other drugs we observed a transient increase in markers of osteoclast activity. This sign of a transient stimulation of osteoclast activity suggests that HD-Sim may be harmful rather than beneficial for MM patients. For this reason and because of gastro-intestinal side effects the study was stopped prematurely.

Local application of statin promotes bone repair through the suppression of osteoclasts and the enhancement of osteoblasts at bone-healing sites in rats

OBJECTIVE

We investigated whether the local administration of simvastatin affected both the cellular events and the bone formation at surgically created bone defects in rat.

STUDY DESIGN

Simvastatin (or a vehicle) was injected into a rat bony defect for 3 consecutive days from the day of surgery. Five or ten days after the injection, new bone tissue was collected, and the gene expressions of bone-related proteins were examined. For the histomorphometry, new bone area was measured.

RESULTS

At day 5, the statin group demonstrated significantly larger new bone area. The number of tartrate-resistant acid phosphatase-positive multinucleated cells in the statin group was less than in the control group. In the statin group, the expressions of both alkaline phosphatase and bone morphogenetic protein 2 mRNA significantly increased. In contrast, the expression of cathepsin K was significantly suppressed in the statin group. Although the levels of both RANK and osteoprotegerin were not affected by statin, the expression of RANKL was depressed. At day 10, there were no significant differences among the groups in either histomorphometric or reverse-transcription polymerase chain reaction analyses.

CONCLUSION

New bone area increased under the influence of simvastatin; however, the effect did not continue when the administration was terminated. Osteoclast suppression may be the consequence of RANKL depression.

The identification of an osteoclastogenesis inhibitor through the inhibition of glyoxalase I

Osteoclasts, bone-resorptive multinucleated cells derived from hematopoietic stem cells, are associated with many bone-related diseases, such as osteoporosis. Osteoclast-targeting small-molecule inhibitors are valuable tools for studying osteoclast biology and for developing antiresorptive agents. Here, we have discovered that methyl-gerfelin (M-GFN), the methyl ester of the natural product gerfelin, suppresses osteoclastogenesis. By using M-GFN-immobilized beads, glyoxalase I (GLO1) was identified as an M-GFN-binding protein. GLO1 knockdown and treatment with an established GLO1 inhibitor in osteoclast progenitor cells interfered with osteoclast generation, suggesting that GLO1 activity is required for osteoclastogenesis. In cells, GLO1 plays a critical role in the detoxification of 2-oxoaldehydes, such as methylglyoxal. M-GFN inhibited the enzymatic activity of GLO1 in vitro and in situ. Furthermore, the cocrystal structure of the GLO1/M-GFN complex revealed the binding mode of M-GFN at the active site of GLO1. These results suggest that M-GFN targets GLO1, resulting in the inhibition of osteoclastogenesis.

Parathyroid Hormone Stimulates Osteoblastic Expression of MCP-1 to Recruit and Increase the Fusion of Pre/Osteoclasts

The clinical findings that alendronate blunted the anabolic effect of human parathyroid hormone (PTH) on bone formation suggest that active resorption is involved and enhances the anabolic effect. PTH signals via its receptor on the osteoblast membrane, and osteoclasts are impacted indirectly via the products of osteoblasts. Microarray with RNA from rats injected with human PTH or vehicle showed a strong association between the stimulation of monocyte chemoattractant protein-1 (MCP-1) and the anabolic effects of PTH. PTH rapidly and dramatically stimulated MCP-1 mRNA in the femora of rats receiving daily injections of PTH or in primary osteoblastic and UMR 106-01 cells. The stimulation of MCP-1 mRNA was dose-dependent and a primary response to PTH signaling via the cAMP-dependent protein kinase pathway in vitro. Studies with the mouse monocyte cell line RAW 264.7 and mouse bone marrow proved that osteoblastic MCP-1 can potently recruit osteoclast monocyte precursors and facilitate receptor activator of NF-kappaB ligand-induced osteoclastogenesis and, in particular, enhanced fusion. Our model suggests that PTH-induced osteoblastic expression of MCP-1 is involved in recruitment and differentiation at the stage of multinucleation of osteoclast precursors. This information provides a rationale for increased osteoclast activity in the anabolic effects of PTH in addition to receptor activator of NF-kappaB ligand stimulation to initiate greater bone remodeling.

Antiresorptive agents and osteoclast apoptosis

Antiresorptive agents have proven to be effective therapies for the treatment of bone diseases associated with excessive osteoclast activity. Decreased osteoclast formation, inhibition of osteoclast actions, and reduced osteoclast survival represent mechanisms by which antiresorptive agents could act. The goals of this article are to present the evidence that antiresorptive agents can decrease osteoclast survival through apoptosis, to review the mechanisms by which they are thought to activate the apoptotic process, and to consider whether the actions on apoptosis fully account for the antiresorptive effects. As background, the apoptotic process will be briefly summarized together with the evidence that factors that promote osteoclast survival affect steps in the process. Following this, therapeutic agents that are both antiresorptive and can stimulate osteoclast apoptosis will be discussed. Other bone therapeutic agents that are either antiresorptive or apoptotic, but not both, will be described. Finally, newer antiresorptive compounds that elicit apoptosis and could represent potential therapeutic agents will be noted.

Chloroform extract of deer antler inhibits osteoclast differentiation and bone resorption

It has been reported that deer antler extract has anti-bone resorptive activity in vivo. However, little is known about the cellular and molecular mechanism of this effect. In this study, we investigated the effects of deer antler extracts on osteoclast differentiation and bone-resorption in vitro. Chloroform extract (CE-C) of deer antler inhibited osteoclast differentiation in mouse bone marrow cultures stimulated by receptor activator of NF-kappaB ligand (RANKL) and macrophage-colony stimulating factor (M-CSF). CE-C suppressed the activation of extracellular signal-regulated kinase (ERK), protein kinase B (PKB/Akt) and inhibitor of kappa B (I-kappaB) by RANKL in osteoclast precursor cells. It also inhibited the bone resorptive activity of differentiated osteoclasts that was accompanied by disruption of actin rings and induction of the apoptosis. These results demonstrate deer antler extract may be a useful remedy for the treatment of bone-resorption diseases such as osteoporosis.

Anabolic agents and the bone morphogenetic protein pathway

A major unmet need in the medical field today is the availability of suitable treatments for the ever-increasing incidence of osteoporosis and the treatment of bone deficit conditions. Although therapies exist which prevent bone loss, the options are extremely limited for patients once a substantial loss of skeletal bone mass has occurred. Patients who have reduced bone mass are predisposed to fractures and further morbidity. The FDA recently approved PTH (1-34) (Teriparatide) for the treatment of postmenopausal osteoporosis after both preclinical animal and clinical human studies indicated it induces bone formation. This is the only approved bone anabolic agent available but unfortunately it has limited use, it is relatively expensive and difficult to administer. Consequently, the discovery of low cost orally available bone anabolic agents is critical for the future treatment of bone loss conditions. The intricate process of bone formation is co-ordinated by the action of many different bone growth factors, some stored in bone matrix and others released into the bone microenvironment from surrounding cells. Although all these factors play important roles, the bone morphogenetic proteins (BMPs) clearly play a central role in both bone cartilage formation and repair. Recent research into the regulation of the BMP pathway has led to the discovery of a number of small molecular weight compounds as candidate bone anabolic agents. These agents may usher in a new wave of more innovative and versatile treatments for osteoporosis as well as orthopedic and dental indications.

Expression of the actin stress fiber-associated protein CLP36 in the human placenta

Differentiation processes in the trophoblast comprise polarization, cell fusion and migration. All these processes involve dramatic reorganizations of cytoskeletal proteins such as intermediate filaments or actin. Due to very restricted knowledge on cytoskeletal changes in trophoblast, we analyzed the protein expression of an actin stress fiber-associated protein, the carboxy-terminal LIM domain protein (CLP36). CLP36 belongs to the enigma family of proteins, binds to alpha-actinin and is involved in the cytoskeletal reorganization and signal transduction of a variety of cells. CLP36 protein was found to be exclusively expressed in the cytotrophoblast layer. Colocalization of CLP36 with Mib-1 revealed that CLP36 protein expression is restricted to proliferative and early post-proliferative trophoblast cells. Blockage of syncytial fusion by culture of villous explants in the presence of caspase 8 inhibitors further supported this notion since CLP36 was only found in the basal and proliferative layer of the multilayered cytotrophoblast. We present evidence for the exclusive protein expression of CLP36 in proliferative and early post-proliferative trophoblast cells. Pathological pregnancy syndromes such as preeclampsia are driven by alterations of trophoblast differentiation and turnover, where it needs to be elucidated whether CLP36 is involved in these alterations.

Effects of garlic oil on postmenopausal osteoporosis using ovariectomized rats: comparison with the effects of lovastatin and 17β-estradiol

The purpose of this study was to examine the antiosteoporosis effects of garlic oil in an ovariectomized (Ovx) rat model of osteoporosis and to compare its efficacy with lovastatin (a synthetic hypocholesterolemic drug) and 17beta-estradiol (a potent antiosteoporotic agent). Animals were divided into five groups: sham-operated control, ovariectomized, ovariectomized supplemented with lovastatin, ovariectomized supplemented with garlic oil and ovariectomized supplemented with 17beta-estradiol. In our study, the development of a high rate of bone turnover and osteoporosis in the ovariectomized animals were confirmed by significant alterations of serum alkaline phosphatase activity, serum tartrate-resistant acid phosphatase activity, urinary excretion of calcium, phosphate, hydroxyproline and urinary calcium to creatinine ratio, when compared with the sham-operated control group. Supplementation of these animals with either garlic oil or lovastatin or 17beta-estradiol, in addition to their hypocholesterolemic effect, could counterbalance all these changes. The results revealed that all three compounds significantly protected the hypogonadal bone loss as reflected by higher bone densities and higher bone mineral contents than the ovariectomized group of animals. The results emphasize that, like 17beta-estradiol, the hypocholesterolemic compounds garlic oil and lovastatin are also effective in suppressing bone loss owing to estrogen deficiency and their efficacy in the order of lower to higher is garlic < lovastatin < 17beta-estradiol.

Hydroxymethylglutaryl-coenzyme A reductase inhibitors and osteoporosis: a meta-analysis

Studies determining the association between hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) and bone metabolism are mixed. We conducted a systematic review to assess the potential impact of statins on fractures, bone mineral density and bone markers. We searched Medline, Embase, the Cochrane Library, and Federal Research in Progress (FEDRIP). Inclusion criteria consisted of human studies with measurable outcomes, which were rated as good or fair according to the United States Preventive Services Task Force (USPSTF) criteria. The effects of statins on bone mineral density (BMD), bone markers and fracture risk were independently extracted by two reviewers and were combined by use of a random-effects model. The 31 analyzed studies included 24 observational studies and seven randomized controlled trials. Overall, statin use was associated with fewer hip fractures (OR 0.60, 95% CI 0.45-0.78) and improved hip BMD (Z score 0.12, 95% CI 0.05-0.19), with a non-significant reduction in vertebral fractures and no effect on vertebral BMD. In subgroup analysis of studies that involved only women there was a reduction in hip fractures (OR 0.75, 95% CI 0.60-0.95) and improvement in hip BMD (Z score 0.11, 95% CI 0.04-0.18). Vertebral BMD was unchanged, and only one study reported on vertebral fractures, finding improvement. Statins had only small effects on bone markers, with a decrease in alkaline phosphatase [standardized mean difference (SMD) -0.18, 95% CI -0.34 to -0.01], an increase in NTX (SMD 0.39, 95% CI 0.07-0.71), with no effect on osteocalcin or CTX. The statistically significant improvement in hip fracture risk was seen only in case-control trials, not in either the eight prospective trials or the two randomized controlled trials (RCTs). Statins may have a beneficial impact on bone metabolism and fracture risk; randomized controlled trials are needed to explore this association.

Inhibitory effects of mevastatin and a geranylgeranyl transferase I inhibitor (GGTI-2166) on mononuclear osteoclast formation induced by receptor activator of NF kappa B ligand (RANKL) or tumor necrosis factor-alpha (TNF-alpha)

We have previously reported that the statin mevastatin (compactin) reversibly inhibits the fusion of TRAP-positive mononuclear preosteoclasts (pOCs) into multinucleated osteoclasts and disrupts the actin ring in mature osteoclasts through the inhibition of protein prenylation. Protein geranylgeranylation, specifically, is known to be required for pOC fusion and for the function and survival of mature osteoclasts. However, it has not been determined whether protein geranylgeranylation is involved in early differentiation of osteoclasts (pOC formation). The current study shows that statins and the geranylgeranyl transferase I inhibitor GGTI-2166 inhibit the pOC formation induced by RANKL or TNF-alpha in cultures of both mouse marrow-derived macrophage-colony-stimulating factor (M-CSF) dependent monocytes (MD cells) and the mouse monocyte cell line RAW 264.7 (RAW cells). Mevastatin, 0.1-0.6 microM, inhibited the formation of pOCs induced by receptor activator of nuclear factor-kappaB ligand (RANKL) or tumor necrosis factor (TNF-alpha) in both cell cultures. The inhibitory effects of mevastatin were overcome by the addition of mevalonate, farnesyl pyrophosphate or geranylgeranyl pyrophosphate. GGTI-2166 inhibited TRAP activity induced by RANKL or TNF-alpha in both cell cultures and prevented the incorporation of [3H]all-trans geranylgeraniol into prenylated proteins in RAW cells. However, the farnesyl transferase inhibitor FTI-2153 did not inhibit TRAP activity although FTI prevented the incorporation of [14C]mevalonate into farnesylated proteins in RAW cells. Clostridium difficile cytotoxin B (toxin B) inhibited pOC formation induced by RANKL or TNF-alpha in both cell cultures. The inhibitory effects of statins and GGTI-2166 on pOC formation may result from the inhibition of the geranylgeranylation of G-proteins, such as Rho or Rac, suggesting that the geranylgeranylation of these proteins is involved in the early differentiation of progenitor cells into pOCs.

HMG-CoA reductase inhibitors and the risk of vertebral fracture

Statins inhibit an enzyme in the mevalonate pathway and therefore may affect bone. In this first study on both symptomatic and nonsymptomatic vertebral fractures in the elderly (N = 3469), we show that long-term statin use is significantly associated with a 50% lower vertebral fracture risk. Randomized trials on statins and fractures, carried out in populations at risk for fractures, are needed.

INTRODUCTION

Statins are cholesterol-lowering agents that could potentially affect bone. Previous studies on statin use and fracture risk reported contradictory results and did not include both symptomatic and nonsymptomatic vertebral fractures.

MATERIALS AND METHODS

To examine the association between statin use, vertebral fractures, and lumbar spine BMD, we performed a prospective population-based cohort study in men and women (N = 3469) > or =55 years of age. These individuals had both baseline and follow-up spinal X-rays available. Statin use was obtained from detailed computerized pharmacy data, and the total number of days of exposure before second X-ray was calculated. A multivariate logistic regression model was fitted to calculate odds ratios and CIs.

RESULTS

During a mean follow-up of 6.5 years, 176 incident vertebral fractures occurred. There were 508 statin users and 16 exposed cases. The adjusted relative risk for incident vertebral fracture in users of statins (compared with nonusers) was 0.58 (95% CI, 0.34-0.99). The relative risk decreased on higher cumulative use to 0.52 (95% CI, 0.28-0.97) for use for more than 365 days during the study period. Use of (the hydrophilic statin) pravastatin and use of nonstatin cholesterol-lowering drugs was not significantly associated with vertebral fracture risk. Statin use was not significantly associated with lumbar spine BMD.

CONCLUSION

Statin use is associated with a lower risk of vertebral fracture. Randomized clinical trials in a population at risk for fracture are needed to examine this association.

Inhibition of osteoclast differentiation and bone resorption by a novel lysophosphatidylcholine derivative, SCOH

Osteoclasts are multinucleated cells formed by multiple steps of cell differentiation from progenitor cells of hematopoietic origin. Intervention in osteoclast differentiation is considered as an effective therapeutic approach to the treatment for bone diseases involving osteoclasts. In this study, we found that the organic compound (S)-1-lyso-2-stearoylamino-2-deoxy-sn-glycero-3-phosphatidylcholine (SCOH) inhibited osteoclast differentiation. The inhibitory effect of SCOH was observed in mouse bone marrow cell cultures supported either by coculturing with osteoblasts or by adding macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor kappaB ligand (RANKL). M-CSF and RANKL activate the ERK, Akt, and NF-kappaB signal transduction pathways, and SCOH suppressed this activation. SCOH also inhibited the bone resorptive activity of differentiated osteoclasts. It attenuated bone resorption, actin ring formation, and survival of mature osteoclasts. Reduced activation of Akt and NF-kappaB and decreased induction of XIAP were observed in mature osteoclasts treated with SCOH. Thus, this novel phosphatidylcholine derivative may be useful for treating bone-resorption diseases.

Statins inhibit osteoblast migration by inhibiting Rac-Akt signaling

Cell migration is a key event in repair and remodeling of skeletal tissues, but the mechanism of osteoblast migration has not been resolved. Statins, which are inhibitors of 3-hydroxy-3-methylglutaryl CoA reductase, increase bone. However, the effect of statins on osteoblast migration remains to be clarified. We investigated the effect of fluvastatin and mevastatin on platelet-derived growth factor (PDGF)-induced migration of osteoblastic MC3T3-E1 cells. PDGF promoted osteoblast migration, while the statins inhibited PDGF-induced migration, and mevalonate and geranylgeranylpyrophosphate but not farnesylpyrophosphate abolished the effect of statins. Dominant-negative Rac severely inhibited PDGF-induced osteoblast migration and reduced Akt phosphorylation. Further, fluvastatin reduced Akt phosphorylation and dominant-negative Akt inhibited PDGF-induced osteoblast migration. These results demonstrate that statins inhibit PDGF-induced osteoblast migration and Rac-Akt signaling plays an important role in the osteoblast migration, and suggest that statins restrain Rac function by inhibiting geranylgeranylation of Rac, which leads to the reduction in Akt activation and osteoblast migration.

HMG-CoA reductase inhibitors in osteoporosis: do they reduce the risk of fracture?

Osteoporosis affects a large number of people in industrialised countries. It has clinical and public-health impacts, most importantly due to subsequent fractures. Osteoporotic fractures are one of the most common causes of disability and are associated with enormous healthcare expenditure. The majority of existing treatment options for osteoporosis only inhibit bone resorption and prevent excessive bone loss but are not capable of stimulating bone formation. However, several recent in vitro and in vivo studies in animals demonstrated that HMG-CoA reductase inhibitors stimulate the production of bone morphogenetic protein (BMP-2), which is a potent regulating protein in osteoblast differentiation and activity. This suggests that HMG-CoA reductase inhibitors may have an anabolic effect on bones, making them a potentially interesting treatment option for osteoporosis. Additionally, several studies in humans showed that some HMG-CoA reductase inhibitors may have a beneficial effect on bone turnover and may lead to an increase in bone mineral density. Consequently, several observational studies tried to evaluate whether use of HMG-CoA reductase inhibitors is associated with a decreased risk of fractures. Even though not all results of these epidemiological studies, using different designs in different study populations, were entirely consistent, they provided substantial evidence that HMG-CoA reductase inhibitor use may decrease the bone fracture risk by approximately 50%. On the other hand, reanalysis of two randomised controlled trials of HMG-CoA reductase inhibitor therapy, designed to assess cardiovascular outcomes, could not show that patients treated with HMG-CoA reductase inhibitors had a lower fracture risk in comparison with placebo-treated patients. Therefore, to conclusively assess the potential of HMG-CoA reductase inhibitors in the prevention and treatment of osteoporosis, randomised controlled trials need to be performed to address this conflicting issue. Until the results of such trials are available, practitioners should prescribe the drugs that have been proven to reduce the risk of osteoporotic fractures.

The calcineurin/nuclear factor of activated T cells signaling pathway regulates osteoclastogenesis in RAW264.7 cells

Although best known for its role in T lymphocyte activation, the calcineurin/nuclear factor of activated T cells (NFAT) signaling pathway is also known to be involved in a wide range of other biological responses in a variety of different cell types. Here we have investigated the role of the calcineurin/NFAT signaling pathway in the regulation of osteoclast differentiation. Osteoclasts are bone-resorbing multinucleated cells that are derived from the monocyte/macrophage cell lineage after stimulation with a member of the tumor necrosis factor family of ligands known as receptor activator of nuclear factor-kappaB ligand (RANKL). We now report that inhibition of calcineurin with either the immunosuppressant drugs cyclosporin A and FK506, or the retrovirally mediated ectopic expression of a specific calcineurin inhibitory peptide, all potently inhibit the RANKL-induced differentiation of the RAW264.7 monocyte/macrophage cell line into mature multinucleated osteoclasts. In addition, we find that NFAT family members are expressed in RAW264.7 cells and that their expression is up-regulated in response to RANKL stimulation. Most importantly, we find that ectopic expression of a constitutively active, calcineurin-independent NFATc1 mutant in RAW264.7 cells is sufficient to induce these cells to express an osteoclast-specific pattern of gene expression and differentiate into morphologically distinct, multinucleated osteoclasts capable of inducing the resorption of a physiological mineralized matrix substrate. Taken together, these data define calcineurin as an essential downstream effector of the RANKL-induced signal transduction pathway leading toward the induction of osteoclast differentiation and furthermore, indicate that the activation of the NFATc1 transcription factor is sufficient to initiate a genetic program that results in the specification of the mature functional osteoclast cell phenotype.

Are Cardiovascular Disease and Osteoporosis Directly Linked?

For years, osteoporosis and cardiovascular disease were thought to be two independent consequences of aging; however, mounting evidence supports an association between these diseases. Recently, a widespread class of cholesterol-lowering drugs known as statins have demonstrated (in rodents and cell cultures) the ability to induce bone formation. This finding is significant since current therapies are limited to the prevention or slowing down of bone loss rather than (enhancing/improving) bone formation. In humans, the ability of statins to generate new bone has not been consistent; however, several investigations have demonstrated a dramatic decrease in fracture risk. Although it has been proposed that statins induce new bone via increased bone morphogenetic protein-2, other conditions affected by statins such as dyslipidaemia, vascular calcification, endothelial dysfunction and impaired nitric oxide expression, may also contribute to the cardiovascular and bone health paradigm. Furthermore, the role of physical activity and its influence on cardiovascular and bone health, especially in postmenopausal women, may contribute to the discrepancy of findings in human data. In summary, it remains to be determined if statins contribute to bone health via improvements in vascular health or by pleiotropic properties unique to their pharmacology. This review provides information on our current understanding of the bone and cardiovascular association, as well as on novel areas of research to further our current understanding of these conditions.

Destruxins, cyclodepsipeptides, block the formation of actin rings and prominent clear zones and ruffled borders in osteoclasts

Bone-resorbing osteoclasts exhibit polarized morphological structures such as actin rings, clear zones, and ruffled borders. To gain insight into the mechanism of bone-resorbing activity of osteoclast and to discover new types of anti-resorptive agents, we have screened for natural compounds that inhibit the bone-resorbing activity of osteoclast-like multinucleated cells (OCLs). Destruxin B (DestB) and E (DestE), cyclodepsipeptides, were found to inhibit pit formation without affecting osteoclast differentiation and survival. Destruxins reversibly induced morphological changes in OCLs in a dose-dependent manner (DestB, 0.2-1 microM; DestE, 0.01-0.05 microM) and inhibited pit formation. Destruxin-induced morphological changes were accompanied by disruption of the actin rings in OCLs. The formation of actin rings in OCLs after adhesion was also inhibited by destruxins. Electron microscopical analysis revealed that destruxin-treated OCLs on dentine slices have no prominent clear zones and ruffled borders. The effective concentrations of destruxins on the morphological changes were almost the same as those that inhibited bone resorption in organ culture system. These results suggest that the anti-resorptive effects of destruxins result from induction of a disorder of the morphological structures in polarized OCLs.

HMG CoA reductase inhibitors and the skeleton: a comprehensive review

Recent studies suggest that the mevalonate pathway plays an important role in skeletal metabolism. HMG CoA reductase inhibitors ("statins"), which inhibit a key enzyme in the mevalonate pathway, are widely used for the treatment of hyperlipidemia. In vitro and animal studies demonstrate that statins stimulate the production of BMP-2, a potent regulator of osteoblast differentiation and activity, suggesting that statins may have an anabolic effect on bone. Statin use in most, but not all observational studies is associated with a reduced risk of fracture, particularly hip fracture, even after adjustment for the confounding effects of age, weight and other medication use. This beneficial effect has not been observed in clinical trials designed to assess cardiovascular endpoints. The effects of statins on bone mass and bone turnover are controversial, but increased bone mass and reduced bone turnover have been observed in controlled studies. Further studies of the skeletal effects of statins are needed, particularly their effects on surrogate markers such as bone mass, bone turnover, and microarchitecture, to determine the optimal formulation, dosing and route of administration. Clinical trials with fracture endpoints are needed before statins can be recommended as therapeutic agents for osteoporosis.

Effects of a selective cyclooxygenase-2 inhibitor, celecoxib, on bone resorption and osteoclastogenesis in vitro

The effects of an important new anti-inflammatory agent, the selective cyclooxygenase-2 inhibitor celecoxib, on bone resorption and osteoclastogenesis elicited by the inflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), the endotoxin lipopolysaccharide (LPS), and the systemic hormones 1alpha,25-dihydroxyvitamin D(3) and parathyroid hormone were examined in vitro. Bone resorption was evaluated by measuring calcium released into the culture medium in a neonatal mouse calvarial bone organ culture. Osteoclastogenesis was evaluated by measuring tartrate-resistant acid phosphatase activity in the cells in cocultures of bone marrow cells and osteoblastic cells and in macrophage-colony-stimulating factor-dependent bone marrow cell cultures. Celecoxib (0.1 microM) completely inhibited the calcium release induced by IL-1beta, TNF-alpha, and LPS. The resorptive effect of 1alpha,25-dihydroxyvitamin D(3) was inhibited partially by celecoxib. In contrast, celecoxib did not inhibit the calcium release elicited by parathyroid hormone or prostaglandin E(2). Celecoxib (0.1 microM) also markedly inhibited osteoclastogenesis induced by these stimulators of bone resorption except for PGE(2) in the coculture system, whereas it failed to inhibit osteoclastogenesis in macrophage-colony-stimulating factor-dependent bone marrow cell cultures. These results indicate that, under certain conditions, cyclooxygenase-2-dependent prostaglandin synthesis is critical for the bone resorption induced by IL-1beta, TNF-alpha, and LPS, and for the osteoclastogenesis induced by these pro-inflammatory molecules and calciotropic hormones. The prevention of prostaglandin synthesis by inflammatory cytokines in bone cells could contribute to the efficacy of celecoxib in preventing bone loss in rheumatoid arthritis.