Warner Chillcott, Amgen, C. Recknor Consulting fees from Zelos, Takeda, Dramatic Health, Novartis, Eli Lilly, Lecture Fees from Amgen, Novartis, Publicis Meetings, M. L. Brandi Grant / Research Support from Amgen, Eli Lilly, NPS, GSK, Roche, Servier, Stroder, Nycomed, Advisory Board Membership of Amgen, MSD, Servier, Eli Lilly, NPS, Nycomed, R. Eastell Grant / Research Support from Novartis, Advisory Board Membership of Novartis, D. Kopperdahl Employee of O.N. Diagnostics, K. Engelke Employee of Synarc, Grant / Research Support from German Research Society, NIH, Paid Instructor for German Osteology Society, T. Fuerst Shareholder of Synarc, Employee of Synarc, H.-S. Radcliffe Employee of Amgen, C. Libanati Shareholder of Amgen, Employee of Amgen, T. Keaveny Shareholder of O.N. Diagnostics, Grant / Research Support from Amgen, Merck, Lilly, Novartis, Advisory Board Membership of Merck, Consulting fees from Merck, Novartis. doi:10.1016/j.bone.2011.03.116 OPC02 Daily nitroglycerin increases bone formation, bone mass, bone structure, and indices of bone strength: A two-year randomized trial S.A. Jamal a , C.J. Hamilton b , R. Eastell c , S.R. Cummings d, ⁎ a Department of Medicine, University of Toronto, Toronto, Canada b Department of Exercise Sciences, University of Toronto, Toronto, Canada c University of Sheffield, Sheffield, UK d San Francisco Coordinating Center, California Pacific Medical Center Research Institute, San Francisco, USA Abstract: Nitric oxide acts on osteoclasts and osteoblasts in vitro. Nitroglycerin (NTG), a nitric oxide donor, prevented bone loss in ovariectomized and steroid-treated mice. Small trials have found that NTG, stimulates bone formation and inhibits bone resorption. Observational studies suggest that intermittent use of nitrates may increase BMD and decrease fracture risk. To determine the effect of NTG on bone turnover, mass, structure and strength, we randomized 243 postmenopausal women with lumbar spine T-scores between 0 and -2.0 to receive 15 mg of NTG ointment or placebo once daily at bedtime for 24 months. Of those randomized, 76% adhered to NTG and 85% to placebo and, overall, 93% completed all 2-year assessments. Bone formation was assessed by serum bone-specific alkaline phosphatase (B- ALP) and resorption by concentrations of N-telopeptide in urine (uNTX). Bone structure and trabecular density in the tibia and radius were measured by pQCT (Norland/Stratec XCT 2000), and indices of bone strength were calculated with the manufacturer's software (Version 6.00). Compared with placebo, daily nitroglycerin increased B-ALP by 21.3% at 1 and 36% at 2 years; it decreased uNTX levels by 31.0% at 12 months and 51% at 2 years (P<0.001 for all). Two years of nitroglycerin increased spine BMD 6.7% (95% CI, 5.2 to 8.2%) and femoral neck BMD 7.0% (5.5 to 8.5%) at 24 months (P<0.001). At the radius and tibia, respectively, NTG increasedtrabecular BMD 11.9% and 8.5%, cortical thickness 13.9% and 24.6%, and periosteal circumference 7.4% and 2.9% (P<0.001 for all comparisons). NTG increased polar section modulus 10.7% and 9.8% and polar moment of inertia 7.3% and 14.5%. Headache was reported by 35% with NTG vs 5% with placebo in the 1st month, but only 5% vs 1% at 1 year. We conclude that daily use of NTG ointment for 2 years uncouples bone formation from bone resorption, forms bone on the periosteal surface, and increases bone density, cortical thickness and indices of bone strength. These results suggest that nitroglycerin may substantially reduce the risk of vertebral and nonvertebral fractures, but this should be tested in a randomized trial. This article is part of a Special Issue entitled ECTS 2011. Disclosure of interest: None declared. doi:10.1016/j.bone.2011.03.117 OPC03 Strontium ranelate positively affects the response of osteocytes to mechanical loading and osteocyte signalling towards osteoclasts A.D. Bakker ⁎ , B. Zandieh-Doulabi, J. Klein-Nulend Oral Cell Biology, ACTA–University of Amsterdam and VU University Amsterdam, Research Institute MOVE, Amsterdam, Netherlands Abstract: Strontium ranelate (SrRan) is a successful treatment for postmenopausal osteoporosis, based on its efficacy in stimulating osteoblasts and inhibiting osteoclasts. Signalling molecules produced by osteocytes in response to mechanical loading, such as nitric oxide (NO) or prostaglandin E 2 (PGE 2 ), mediate the number and activity of osteoblasts and osteoclasts. The aim of this study was to assess the effect of SrRan on paracrine signalling from mechanically stimulated osteocytes towards osteoclasts. MLO-Y4 osteocytes were cultured for 24 h in the presence of SrRan up to 3 mM, and either or not stimulated with 60 min of pulsating fluid flow (PFF). Treatments effects were assessed by quantification of NO (Griess), adenosine tri-phosphate (ATP; Luminescence) and PGE2 (ELISA) in the culture medium, and by quantification of mRNA expression (taqman PCR) of COX2 (key enzyme for PGE 2 production), cx43 (constituent of gap junctions and hemichannels), RANKL, OPG and M-CSF (mediating osteoclast formation). Apoptosis was assessed using Caspase-Glo 3/7 Assay, since apoptotic osteocytes can stimulate osteoclas- togenesis. Medium from SrRan and/or PFF-treated osteocytes was added to cultured mouse bone marrow cells. After 7 days TRACP-positive multinucleated cells (osteoclasts) were counted. SrRan did not affect apoptosis or ATP release by osteocytes. 3 mM SrRan stimulated NO and PGE2 production by osteocytes in both static (1.6 and 2.8-fold, respectively) and PFF-stimulated conditions (1.3 and 2.6-fold, respectively), showing that SrRan enhances osteocyte signalling. SrRan did not affect COX2, cx43 or M-CSF expression at any concentration tested. Conditioned medium from osteocytes treated with 3 mM SrRan inhibited osteoclastogenesis by 1.9-fold compared to conditioned medium from non-treated osteocytes. The combination of 3 mM SrRan and PFF strongly inhibited osteocyte-stimulated osteoclastogenesis (4.3 fold), concomitantly with an enhanced osteocyte OPG/RANKL ratio (2.9-fold). In conclusion, SrRan positively affects paracrine signalling between osteocytes and osteoclasts. The positive effects of SrRan on bone mass may be at least partly explained by improved paracrine signalling by the most abundant cell in bone, the osteocyte. This article is part of a Special Issue entitled ECTS 2011. Disclosure of interest: A. Bakker Grant / Research Support from Servier, France, B. Zandieh- Doulabi Grant/Research Support from Servier, France, J. KleinNulend Grant/Research Support from Servier, France. doi:10.1016/j.bone.2011.03.118 OPC04 Transmenopausal changes in osteocyte lacunar volume in adult human trabecular bone D.B. Kimmel a, ⁎ , M.P. Akhter a , R. Recker a , T. Fong b , J. Coats b a Osteoporosis Research Center, Creighton University, Omaha, NE, USA b Xradia, Inc., Pleasanton, CA, USA Abstract: Osteocytes (Ot) respond to pharmacologic/mechanical stimuli by altering their lacunar volume. Synchrotron radiation (SR) scanning (0.7 μm pixel resolution [PR]) allows 3D imaging of whole Ot lacunae (Ot.La). The smallness of Ot.La causes current laboratory 3D imaging devices difficulty in resolving them in intact bone samples. Here, we quantify the effect of estrogen status on Ot.La volume (Ot.LaV) in various trabecular bone microarchitectural regions with a lab-based 3D imaging instrument that achieves SR-like resolution. Transilial biopsy specimens were taken from opposite sides of a healthy woman before menopause and at one year after her last menses. Each was embedded undecalcified in plastic. Histomorphometry showed seven-fold higher remodeling after menopause. A portion of each specimen remaining after sectioning was trimmed to 2 × 2× 8 mm and scanned at 5 μm PR with a 3D X Ray Microscope. 3D images were reconstructed. Ten volumes of interest (VOIs; 0.9 mm diameter × 0.5 mm long; 4 pre- and 6 post-menopausal) containing trabecular nodes or struts were selected and scanned at ~0.6 μm PR. The 3D image of each VOI was analyzed by segmentation software (Ratoc; Tokyo, JP) for individual Ot.LaV (iOt.LaV). Ot.La were taken as discrete bone tissue voids > 50 and < 500 μm³. All Ot.La of like menopausal status and microarchitectural location were pooled and analyzed by two factor ANOVA. 9093 Ot.La were examined. iOt.LaV was 11% lower in post-menopausal specimen struts than pre-menopausal struts (P<.0001) (Table 1). Ot.LaV did not change in nodes. Struts and nodes differ significantly in their Ot.LaV behavior across menopause. Study of these and other transmenopausal pairs continues. Table 1 Location Pre-Meno iOt.LaV Post-Meno iOt.LaV Struts 170±117 (2 [1848]) 151±107 (4 [3431])* Nodes 172±119 (2 [2394]) 170±109 (2 [1420]) Units(iOt.LaV) =μm 3 ; Mean ± SD; (# of VOIs [total number of Ot.La in sample]). *Diff from Pre-Meno (P < .0001). These data suggest that Ot.LaV in bone tissue decreases with menopause in trabecular struts, but not nodes. Bone tissue with smaller Ot.La could have less ability to intercept propagating microcracks, creating decreased toughness on a sub-microscopic level not detectable by current methods. These results also parallel rat data that indicate smaller Ot. LaV in trabecular bone of OVX than intact rats. Decreased toughness concentrated in trabecular struts may also be an additional reason why struts are preferentially lost with menopause and aging. This article is part of a Special Issue entitled ECTS 2011. Disclosure of interest: D. Kimmel Consulting fees from Xradia, Inc., M. Akhter Consulting fees from Xradia, Inc., R. Recker: None Declared, T. Fong Employee of Xradia, Inc., J. Coats Employee of Xradia, Inc. doi:10.1016/j.bone.2011.03.119 Abstracts / Bone 48 (2011) S86–S90 S87