Roles of Orphan Nuclear Receptor Small Heterodimer Partner in Bone Development: Microcomputed Tomographic Analysis of Bone Microarchitecture in SHP Knockout Mice / 대한골다공증학회지

ABSTRACT

OBJECTIVES: Orphan nuclear receptor small heterodimer partner (SHP) is involved in osteoblastic differentiation. This study was undertaken to demonstrate a role of SHP in in vivo bone development using microcomputed tomographic (microCT) analysis of SHP knockout (KO) mice. MATERIAL & METHODS: Tibia bones were harvested from 1-, 4-, 8- and 20-week-old wild type (WT) and SHP KO mice. The microarchitecture of tibial bone was analyzed using a microCT (Skyscan 1172; Skyscan, Kontich, Belgium). Samples were scanned at a resolution of 17 microm (isotropic). The X-ray was operated with 50 kV, 200 microA of energy, 1.2 sec of exposure time, and a 0.5 mm thick aluminum filter. Projections were acquired over an angular range of 180degrees. For quantification of the bone mineral density (BMD), the microCT was calibrated using 2 standard phantoms with densities of 0.25 and 0.75 g/cm3. The image slices were reconstructed and analyzed using CT analyzer software (CTan, Skyscan). RESULTS: The CT values of tibial trabecular bone were significantly decreased in SHP KO compared to WT at 20-week-old mice determined by microCT; (bone volume / tissue volume [BV/TV, 40%], BMD [80%], and trabecular number [Tb.N, 50%]). However, the CT values were not significantly different between WT and SHP KO in cortical bone. Furthermore, the qualitative indices of trabecular bone such as the structure model index (SMI) and the polar moment inertia (PMI) did not differ between WT and SHP KO mice. CONCLUSION: These microCT results supports that SHP may act as a positive regulator of trabecular bone formation.