Socrates Papapoulos

Bisphosphonates inhibit the adhesion of breast cancer cells to bone matrices in vitro.

Bisphosphonates are used with increasing frequency in the management of skeletal complications in patients with breast cancer. In this paper, we have investigated whether bisphosphonates, besides their known beneficial effects on tumor-associated osteoclastic resorption, are capable of inhibiting breast cancer cell adhesion to bone matrix. For that we used two in vitro models for bone matrix (cortical bone slices and cryostat sections of trabecular bone from neonatal mouse tails). Four bone matrix-bound nitrogen-containing bisphosphonates (pamidronate, olpadronate, alendronate, and ibandronate) inhibited adhesion and spreading of breast cancer cells to bone dose-dependently, whereas etidronate and clodronate had little or no effect. Strikingly, the relative order of potency of the bisphosphonates in inhibiting the adhesion of cancer cells to cortical and trabecular bone corresponded to their relative antiresorptive potencies in vivo as well as their ranking in in vitro bone resorption assays with predictive value for their clinical efficacy. It appears that nitrogen-containing bisphosphonates alter selectively the adhesive properties of the extracellular bone matrix preventing the attachment of breast cancer cells to it. Besides the beneficial effects of bisphosphonates on tumor-induced osteoclastic resorption, the previously unrecognized effect presented in this paper makes these agents suitable for earlier pharmacologic intervention in patients with breast cancer at risk of developing bone metastases.

Inducible production of nitric oxide in osteoblast-like cells and in fetal mouse bone explants is associated with suppression of osteoclastic bone resorption.

Nitric oxide (NO) has been suggested to be involved in the regulation of osteoclast activity. Since osteoblasts, through the release of various factors, are the main regulators of osteoclastic resorption, first we have investigated whether osteoblast-like cells and fetal mouse long bone explants are able to produce NO. Second, we have assessed the effect of NO on osteoclastic resorption in whole bone cultures. In this study we show that primary rat osteoblast-like cells as well as the clonal rat osteoblast-like cell line UMR-106, stimulated with IFN-gamma together with TNF-alpha and LPS, produce NO, measured as nitrite production. IL-1 alpha enhanced while TGF-beta 2 inhibited TNF-alpha + IFN-gamma + LPS-stimulated NO production in UMR-106 cells dose dependently. Both the cytokines, however, had no effect when given alone. The competitive inhibitor of NO production, NG-monomethyl-arginine (L-NMMA), and cycloheximide abolished the increase in nitrite production induced by TNF-alpha + IFN-gamma + LPS, while hydrocortisone had no effect, as previously reported for chondrocytes. Calciotropic hormones had either no effect [1,25(OH)2D3] or had a small inhibitory effect (parathyroid hormone) on stimulated NO production. Furthermore, we found that in cultured fetal mouse long bone explants the combination of TNF-alpha + IFN-gamma + LPS as well as the NO donor sodium nitroprusside could inhibit osteoclastic resorption, measured as 45Ca release. The inhibition of resorption was prevented by concurrent administration of L-NMMA. Histological evaluation revealed that the TNF-alpha + IFN-gamma + LPS-induced inhibition of 45Ca release was associated with a decrease in the number of tartrate-resistant acid phosphatase-positive osteoclasts. We propose that the NO production by osteogenic cells (osteoblasts and chondrocytes) may represent an important regulatory mechanism of osteoclastic activity especially under pathological conditions characterized by release of bone-resorbing inflammatory cytokines.

Diagnosis and management of osteoporosis in postmenopausal women: Clinical guidelines

The authors, all physicians involved in clinical research on bone and practicing clinicians, propose practical guidelines for identifying persons with osteoporosis or those at high risk of developing the disease and for managing patients who may benefit from therapy. These guidelines are based on an analysis of peer-reviewed articles published before November 1998. A flowchart of women who might benefit from treatment is provided, including clinical presentation (recent fracture of the spine, hip, or other bone or no fracture; risk factors for osteoporosis); relevant investigations (bone mineral density measurement and laboratory tests required for the differential diagnosis); and therapeutic management (general measures such as calcium and vitamin D supplementation and specific pharmacologic interventions such as estrogen, bisphosphonates, intranasal calcitonin, raloxifene, fluoride salts, and other compounds that have been assessed in randomized clinical trials). The strongest evidence for antifracture efficacy (reduction of vertebral and nonvertebral fracture risk) was observed with alendronate.

Binding and antiresorptive properties of heterocycle-containing bisphosphonate analogs : Structure-activity relationships

To define structure-activity relationships for bisphosphonate activity, we examined the bone binding and antiresorptive properties of heterocycle-containing analogs of risedronate, a pyridylbisphosphonate, in cultures of mouse fetal bone explants. Our studies indicated that hydroxybisphosphonates with the nitrogen molecule in the pyridyl ring were very potent inhibitors of osteoclastic resorption. Changing the place of the nitrogen in the ring structure of risedronate or its methylation did not significantly alter antiresorptive potency in relation to risedronate. Extension of the R2 chain, however, reduced efficacy. In binding experiments, we found that all heterocyclic bisphosphonates with a hydroxyl group in R1 had comparable affinity for bone mineral and inhibited calcium incorporation into bone explants to a similar extent. The affinity of a risedronate analog without R1 was markedly reduced. We also examined the properties of a risedronate analog (NE-10790) belonging to the group of phosphonocarboxylates in which one of the phosphonate groups is substituted by a carboxyl group. NE-10790 had strongly reduced binding affinity, but still retained some antiresorptive activity. Interestingly, the continuous presence of NE-10790 in cultures of fetal mouse metacarpal bones increased its antiresorptive efficacy by about 40-fold compared with 24 h preincubation, whereas, under the same conditions, the potency of high-affinity hydroxybisphosphonates did not change or only slightly increased. This may be explained by the differences in pharmacokinetic behavior between compounds of high and of low affinity for bone mineral. These data show that, as with alkylbisphosphonates, heterocycle-containing bisphosphonates with a nitrogen functionality in the R2 chain are potent antiresorptive agents and a hydroxyl substitution in the R1 chain confers high affinity for bone mineral, probably due to tridentate configuration. The group of phosphonocarboxylates, with strongly reduced bone affinity, provides an interesting therapeutic option.

Interleukin 17 synergises with tumour necrosis factor α to induce cartilage destruction in vitro

Background: Interleukin 17 (IL17) is produced by activated T cells and has been implicated in the development of bone lesions and cartilage degradation in rheumatoid arthritis (RA). Objective: To determine whether IL17, alone or together with tumour necrosis factor α (TNFα), induces cartilage destruction in vitro. Methods: Fetal mouse metatarsals stripped of endogenous osteoclast precursors were used to study the effect of IL17 on cartilage degradation independently of osteoclastic resorption. Cartilage destruction was analysed histologically by Alcian blue staining. Results: IL17 alone, up to 100 ng/ml, had no effect on the cartilage of fetal mouse metatarsals. IL17 (≥0.1 ng/ml), however, induced severe cartilage degradation when given together with TNFα (≥1 ng/ml). The cytokine combination decreased Alcian blue staining, a marker of proteoglycans, throughout the metatarsals and induced loss of the proliferating and early hypertrophic chondrocyte zones. TNFα alone also decreased Alcian blue staining, but not as dramatically as the cytokine combination. In addition, it did not induce loss of chondrocyte zones. Treatment with inhibitors of matrix metalloproteinase (MMP) activity and nitric oxide synthesis showed that MMP activity played a part in cartilage degradation, whereas nitric oxide production did not. Conclusions: IL17, together with TNFα, induced cartilage degradation in fetal mouse metatarsals in vitro. IL17 may, therefore, participate in the development of cartilage destruction associated with RA by enhancing the effects of TNFα and may provide a potential therapeutic target.

Sclerostin in Mineralized Matrices and van Buchem Disease

Sclerostin is an inhibitor of bone formation expressed by osteocytes. We hypothesized that sclerostin is expressed by cells of the same origin and also embedded within mineralized matrices. In this study, we analyzed (a) sclerostin expression using immunohistochemistry, (b) whether the genomic defect in individuals with van Buchem disease (VBD) was associated with the absence of sclerostin expression, and (c) whether this was associated with hypercementosis. Sclerostin was expressed by cementocytes in mouse and human teeth and by mineralized hypertrophic chondrocytes in the human growth plate. In individuals with VBD, sclerostin expression was absent or strongly decreased in osteocytes and cementocytes. This was associated with increased bone formation, but no overt changes in cementum thickness. In conclusion, sclerostin is expressed by all 3 terminally differentiated cell types embedded within mineralized matrices: osteocytes, cementocytes, and hypertrophic chondrocytes.

The prevalence of low bone mineral density in dutch perimenopausal women : The Eindhoven perimenopausal osteoporosis study

Abstract: The aim of this study was to estimate the prevalence of osteopenia and osteoporosis in perimenopausal women, and to assess determinants of low bone mineral density (BMD). All women born between 1941 and 1947 (aged between 46 and 54 years) living in the city of Eindhoven were invited to participate in the study; 5896 white Dutch women, representing 73% of the total number of Dutch women in this age group, were studied. Of these, 24% were using estrogen preparations and 19% had undergone hysterectomy, with or without oophorectomy. All women were interviewed and bone mineral density (BMD) of the lumbar spine was measured by dual-energy X-ray absorptiometry (DXA). Osteopenia and osteoporosis were defined according to the criteria proposed by a WHO working group. In the population studied the prevalence of osteopenia and osteoporosis was 27.3% and 4.1%, respectively. With progression from premenopause to menopause, the prevalence of osteoporosis increased from 0.4% to 12.7%, and that of osteopenia from 14.5% to 42.8%. An increased risk for low BMD (osteopenia and osteoporosis) was associated with age, menopausal status and smoking, while alcohol consumption, high body mass index (BMI) and use of estrogens had a protective effect. This study of a large population-based cohort of perimenopausal women revealed a high prevalence of low bone mass and, therefore, a higher risk for osteoporotic fractures. The data further suggest that, when issues on the long-term efficacy and safety of preventive treatments are resolved, it may be possible to identify women at higher risk who are most likely to benefit from screening strategies.

New insights into the role of vitamin D and calcium in osteoporosis management: an expert roundtable discussion.

ABSTRACT Background: Adequate vitamin D and calcium nutrition play a critical role in the maintenance of musculoskeletal health and are considered the first step in osteoporosis treatment. Roundtable discussion: In February 2008 Merck Sharp & Dohme sponsored a 2-day, evidence-based expert panel on the benefits of vitamin D for the patient with osteoporosis and the role of vitamin D in combination with antiresorptive therapy for the management of osteoporosis. One of the primary objectives of the meeting was to review new data on the optimal serum 25-hydroxyvitamin D [25(OH)D]levels. The symposium was attended by 29 researchers and clinicians from Europe and the Middle East. The discussion focused on optimizing vitamin D and calcium nutrition and reducing falls and fractures in osteoporotic patients. Conclusions: Current evidence and expert opinion suggests that optimal serum 25(OH)Dconcentrations should be at least 50u2009nmol/L (20u2009ng/mL) in all individuals. This implies a population mean close to 75u2009nmol/L (30u2009ng/mL). In order to achieve this level, vitamin D intake of at least 20u2009µg daily is required. There is a wider therapeutic window for vitamin D than previously believed, and doses of 800u2009IU per day, regardless of sun exposure, season or additional multivitamin use, appear to present little risk of toxicity. Apart from fracture and fall prevention, optimization of vitamin D status may also have additional general health benefits. Based on newly emerging data regarding calcium supplementation, and recommendations for increased vitamin D intake, the current recommendations for calcium intake in postmenopausal women may be unnecessarily high. In addition to vitamin D and calcium, treatment of patients with osteoporosis at high risk of fractures should also include pharmacologic agents with proven vertebral and non-vertebral fracture efficacy.

Patients with Primary Hyperparathyroidism Have Lower Circulating Sclerostin Levels than Euparathyroid Controls

OBJECTIVEnIn vitro and in vivo studies in animal models have shown that parathyroid hormone (PTH) inhibits the expression of the SOST gene, which encodes sclerostin, an osteocyte-derived negative regulator of bone formation. We tested the hypothesis that chronic PTH excess decreases circulating sclerostin in humans.nnnDESIGNnWe studied 25 patients with elevated serum PTH concentrations due to primary hyperparathyroidism (PHPT) and 49 patients cured from PHPT after successful parathyroidectomy (PTx; euparathyroid controls (EuPTH)).nnnMETHODSnWe measured plasma PTH and serum sclerostin levels and the serum markers of bone turnover alkaline phosphatase, P1NP, and β-CTX.nnnRESULTSnAs expected by the design of the study, mean plasma PTH was significantly higher (P<0.001) in PHPT patients (15.3 pmol/l; 95% confidence interval (CI): 11.1-19.5) compared with that of EuPTH controls (4.1 pmol/l; 95% CI: 3.6-4.5). PHPT patients had significantly lower serum sclerostin values compared with those in EuPTH subjects (30.5 pg/ml; 95% CI: 26.0-35.1 vs 45.4 pg/ml; 95% CI: 40.5-50.2; P<0.001) and healthy controls (40.0 pg/ml; 95% CI: 37.1-42.9; P=0.01). Plasma PTH concentrations were negatively correlated with serum sclerostin values (r=-0.44; P<0.001). Bone turnover markers were significantly correlated with PTH, but not with sclerostin.nnnCONCLUSIONnPatients with PHPT have significantly lower serum sclerostin values compared with PTx controls with normal PTH concentrations. The negative correlation between PTH and sclerostin suggests that SOST is downregulated by PTH in humans.

Report on osteoporosis in the European community: Current status and recommendations for the future

The morbidity and mortality attributable to osteoporotic fractures and their high financial costs are well documented. In recent years there has been significant progress in our knowledge of the causes, diagnosis and treatment of osteoporosis but these have not always been fully exploited by health care systems and much remains to be learned. Although awareness of the enormous suffering and medical, social and financial burden created by osteoporosis has grown, insufficiently high priority is currently given to the disease by governments and health care providers. This has resulted in inadequate provision of diagnostic facilities in many European Union member states and failure to provide optimal care for all individuals suffering from osteoporosis. To address these concerns, a Working Party of experts from the European Union member states was set up by the European Commission Directorate General V to produce a report on osteoporosis. The Report on Osteoporosis in the European Community provides a detailed analysis of the epidemiology, pathogenesis and clinical management of the disease throughout the European Union with particular emphasis on prevention in the future. The report examines differences between member states with regard to prevalence and incidence of osteoporotic fractures, future demographic changes, nutrition, diagnostic resources and patient support groups. A number of specific recommendations are made that are primarily targeted at improving prevention of osteoporosis and reallocating health care resources to meet the growing demands in the future. This paper provides a summary of the contents of the report and concludes with the recommendations of the Working Party.