relevant for population studies in Asian and other ethnic groups worldwide. doi:10.1016/j.bone.2010.09.213 209 Assessment of bone marrow oxygenation based on T 2 * and T 2 changes following oxygen inhalation David K.W. Yeung 1 , James Griffith 1 , Yi-xiang Wang 1 , Jing Yuan 1 , Queenie Chan 2 , Heather T. Ma 1 1 Imaging and Interventional Radiology, The Chinese University Of Hong Kong, Hong Kong, China 2 Philips Healthcare, Wan Chai, China Background: Osteoporosis affects 1 in 4 women and 1 in 8 men over 50 years. Despite that the risk factors and biological processes leading to bone loss have been well studied, little is known about the mechanisms that initiate bone loss in the first place. Osteocytes, marrow adipocytes and hematopoietic cell lines share a common precursor in the marrow mesenchymal stem cell (MSC) which can variably differentiate along osteoblastic, adipocytic or hematopoietic cell lines. The level of oxygenation within bone marrow may affect the pattern of MSC differentiation. On the other hand, a shift in the pattern of MSC differentiation might be observed indirectly by a change in the demand for oxygen in the bone marrow. Therefore, the development of an MR-based technique to study marrow oxygena- tion non-invasively might be helpful to further our understanding on marrow physiology and bone formation. Objective: MR relaxometry (T 2 * and T 2 ) techniques have been shown to be useful in osteoporosis studies. Patients with osteoporosis have prolonged marrow T 2 * due to reduced magnetic field inhomogeneities in less dense trabecular bone. Accumulation of fatty marrow in osteoporotic bone is believed to increase the marrow T 2 of subjects with reduced BMD. Deox- yhemoglobin is paramagnetic and breathing carbogen or pure oxygen lowers deoxyhemoglobin concentration and increases both T 2 * and T 2 of water in blood and in the tissue surrounding blood vessels. Our aim in this study was to verify whether oxygen inhalation has a measurable effect on bone marrow T 2 * and T 2 relaxation times. Materials and methods: Seven healthy volunteers (4 M/3 F; mean age 35 years) were examined in the supine position on a 3.0T MRI scanner. Air or 100% oxygen was delivered via a tight-seal full-face mask at a rate of 15 L/min. A 10 mm thick axial image was acquired from each vertebral body L3, L4 and L5 for relaxation measurements before (T 2 * air and T 2 air) and after 5 min of oxygen inhalation (T 2 * oxygen and T 2 oxygen). For a given vertebral body, the same region of interest was drawn on the T 2 * and T 2 maps to obtain mean T 2 * air, T 2 * oxygen, T 2 air and T 2 oxygen. Paired t-test was used to evaluate differences T 2 * air vs. T 2 * oxygen and T 2 air vs. T 2 oxygen with differences considered significant at p < 0.05. Results: Twenty-one pairs of T 2 * and T 2 values before and after breathing oxygen were obtained from the 3 vertebral bodies of all 7 subjects. On average, T 2 * increased by11.7% as compared to 7.9% for T 2 . Pair t-test showed that there were significant differences in T 2 * (p =0.002) and T 2 (p <0.0001) values when breathing air or oxygen. Conclusion: T 2 * changes after breathing carbogen or oxygen have been used to study tumor vascular architecture. Our results were the first to report that similar effects can be observed in the human bone marrow. Oxygen- rich blood transported into the marrow cavity reduced the amount of deoxyhemoglobin in the marrow vasculature and surrounding tissues thereby prolonging marrow T 2 * and T 2 . Apart from susceptibility differences at the marrow-bone boundaries influencing T 2 * decay, iron-rich red bone marrow might also play a role. T 2 * change (11.7%) was higher than T 2 change (7.9%) after oxygen inhalation probably due to higher oxygen demand (and blood supply) in the red marrow as compared to fatty marrow. Further studies involving subjects with different BMD are necessary to confirm our initial results. doi:10.1016/j.bone.2010.09.214 212 Effects of Formulat Bushenzhuanggu on the biochemical markers of bone metabolism and the bone mineral density in ovariectomized rats Yan Liu, Hong Chang The Hospital of Inner Mongolia Medical College, China Objective: To investigate the effects of Formulat Bushenzhuanggu on the biochemical markers of bone metabolism, the bone mineral density and the pharmacological mechanism. Methods: The ovar- iectomized rat model was used. The bone mineral density and the biochemical markers of the rats, including E 2 , ALP and BGP in serum were investigated. The results were compared among the model group, sham-operated group and the diethylstilbestrol (DE) group. Results: The concentrations of ALP and BGP in Formulat Bushenz- huanggu and DE groups of each dosage were significantly higher than that of the sham-operated group (p < 0.05) and lower than that of the model group (p < 0.05), and the concentration of E 2 was lower (p>0.05). The levels of DPD and PTH were lower than those of the model group (p < 0.05). The bone mineral density in the femur was significantly higher in every medication group than that in the model group. Conclusion: P Formulat Bushenzhuanggu is effective in inhibiting bone resorption, delaying the bone loss in ovariectomized rats and has the preventive and therapeutic effect on osteoporosis. doi:10.1016/j.bone.2010.09.215 214 A novel peptide for a drug delivery system to preferentially target bone formation sites Heng Wu, Ge Zhang, Bao Sheng Guo, Tang Tao, Gang Li, Kwong Man Lee, Leung Kim Hung, Ling Qin Chinese University of Hong Kong, Hong Kong, China Objective: At present, there is still lack of a drug delivery system specifically targeting bone formation site to understand clinical translation for bone formation. Aspartate–serine–serine (DSS) 6 was found to effectively bind to amorphous calcium phosphonate in vitro. Interestingly, amorphous calcium phosphonate is the major character- istic of the bone formation surface. Therefore, the objective of our study is to explore and evaluate the (DSS) 6 -containing peptide as a novel molecule for targeting a bone formation site. Methods: The binding of Fluorescein (FITC) labeled peptides to hydroxyapatite (HA) with different crystallinity was investigated in vitro and (Aspartic acid) 8 (Asp 8 ), a common bone-targeted molecule, was employed as a control. Human osteoblasts were cultured under osteogenic conditions and treated with Asp 8 or (DSS) 6 and the binding to surface of mineralizing nodules was visualized by fluorescence microscopy. Xylenol Orange was administrated to the mice to label the bone formation sites. At 24 h after administration of FITC-labeled peptides, the mice were sacrificed and the femurs were taken out for processing of un-decalcified tissue sections. The appearance incidence of FITC and its fluorescence intensity at bone formation sites was examined. Results: In HA binding assay, FITC-labeled (DSS) 6 exhibited strong binding to HA with low crystallinity. By contrast, FITC-labeled Asp 8 showed significant advantages in high crystalline HA, which indicated that (DSS) 6 favorably binded to HA with low crystallinity. The cell Abstracts / Bone 47 (2010) S385–S458 S413