μCT measurements.

μCT scanning and analysis was performed using a Scanco μCT-40 scanner, as previously reported (18, 63, 64). Settings used for the in vitro scans are as follows: 70 kVp 114uA, 8W with an integration time of 200 ms with a voxel size of 12 μm³ for femurs from 12-week-old mice, and a voxel size of 10.5 μm³ for femurs from 7-month-old mice. For the femoral trabecular region, we analyzed 70 slices, beginning 50 slices from the distal growth plate. Femoral cortical bone was measured using 80 continuous CT slides located at the femoral midshaft. We used the thresholding approach described by Bouxsein et al. (65), which is recommended by Scanco and includes a visual inspection and comparison of preview and slice-wise grayscale 2D images. The same threshold value was used for all measurements.