The 18 kDa Translocator Protein (Peripheral Benzodiazepine Receptor) Expression in the Bone of Normal, Osteoprotegerin or Low Calcium Diet Treated Mice

The presence of the translocator protein (TSPO), previously named as the mitochondrial or peripheral benzodiazepine receptor, in bone cells was studied in vitro and in situ using RT-qPCR, and receptor autoradiography using the selective TSPO ligand PK11195

Quantification of [³H]PK11195 binding in mice with altered bone turnover.

<p>The regional binding in the sub-growth plate spongiosa is quantitatively expressed as tissue equivalent activities (Bq/mg; N = 4/group). A significant difference (*) is observed between animals with OPG and low calcium diet treatments (p = 0.01, one-way ANOVA with Tukey's multiple comparison test). Error bar = standard deviation.</p

TSPO mRNA expression in bone.

<p>(A) Lanes 1 and 5 show 100 bp DNA ladders. TSPO mRNA is detected in the whole bone tissue of a normal mouse (lane 4). Restriction enzyme assay was used to confirm the specificity of the result. PCR products of expected band sizes are produced from the digestion by NcoI (lane 2) and PvuII (lane 3). (B) shows the expressions of TRAP, (C) the expression of ALP and (D) the expression of TSPO mRNA in primary osteoclast and osteoblast cultures and in skeletal muscle (N = 3). OB = primary osteoblast culture from calvaria; OC = primary osteoclast culture from spleen cells treated with M-CSF/RANKL. Error bar = standard deviation.</p

The gelatin phantom to simulate partial volume loss and spillover effect <i>in vivo</i>.

<p>The dashed line represents the centre of the microPET axial field of view and is positioned 4 mm from the interface between the region containing 8 MBq and the region containing 15 MBq of activity. The red box shows the region affected by spillover effect. The blue boxes are the areas affected by partial volume losses due to the small volume of the structure.</p

[¹⁸F]fluoride uptake measured by microPET.

<p>[¹⁸F]fluoride uptake is expressed in SUV for left femur (A), right femur (B) and both femurs together (C) (N = 4/group). Error bar = standard deviation. A significant group difference between OPG-treated and low calcium diet animals can be seen in the pooled bone data. However, the differences are small and not consistent if right and left femurs are compared separately (<i>right and left femurs</i>: OPG-treated = 22.4±1.9; low calcium diet = 24.73±1.76, p = 0.023; <i>left femur</i>: OPG-treated = 21.91±1.74; low calcium diet = 24.76±1.47, p = 0.046; <i>right femur</i>: OPG-treated = 22.89±2.18; low calcium diet = 24.7±2.25, p = 0.293).</p

Steps for defining the sub-growth plate spongiosa as the ROI in a bone autoradiograph.

<p>(A) The growth plate is readily identified as a landmark. (B) shows the consistent expansion of 400 µm around the initially defined landmark structure of the growth plate (C) and the resultant delineation of the sub-growth plate spongiosa.</p

Partial volume loss in a small region of interest.

<p>The middle portion of the narrow end of the glass Pasteur pipette is a region with high partial volume loss and corresponds to planes 7 to 16 in the activity profile (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030623#pone-0030623-g008" target="_blank">Figure 8B</a>). The wide end of the glass Pasteur pipette is a large volume with minimal partial volume loss and corresponds to planes 58 to 67 in the activity profile (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030623#pone-0030623-g008" target="_blank">Figure 8B</a>). The percentage of partial volume losses are more pronounced when the overall activity in the phantom is low, i.e. 68% loss in the 1 MBq-phantom compared to 54% loss in the 8 MBq-phantom.</p