Prednisone prevents particle induced bone loss in the calvaria mouse model

Abstract

Introduction: Glucocorticoids are essential in the treatment of many chronic inflammatory and malignant diseases but are known to have detrimental effects on bone. This study aimed to investigate the effects of prednisone on osteoclast functioning in vivo in the calvaria particle-induced bone loss mouse model.

Methods: 12-week-old male C57BL6/J mice received subcutaneously implanted prednisone (2.5 mg/d, 60 day release (n = 14)) or placebo pellets (n = 10). Osteolysis of the calvaria bone was induced two weeks later by application of ultra-high-molecular-weight polyethylene- (UHMWPE) particles to the dome (vs sham operation). The extent of osteolysis was determined histologically and by micro-computer tomography.

Results: Prednisone significantly inhibited particle-induced osteolysis in the skull. No significant difference in osteoclast numbers was seen in mice with prednisone vs placebo treatment. Prednisone treatment alone without particle application did not reduce bone mineral density or deterioration in bone microarchitecture parameters.

Conclusions: The calvaria particle-induced bone loss mouse model can be adapted to investigate osteoclast activity in vivo and the effect of prednisone on osteoclasts. In this preventive experimental design, the application of short-term low-dose prednisone has osteoprotective effects without measurable systemic side effects on bone parameters.

Keywords: Bone; Glucocorticoids; In-vivo; Inflammation; Osteoclasts.

Figure 1

3D-Reconstruction. 3D-Reconstruction of micro-CT analysis of the calvaria of (A) placebo treated sham operated mice (B) placebo treated mice with particle induced osteolysis, (C) sham operated mice, treated with prednisone and (D) lack of particle induced osteolysis in mice treated with prednisone.

Figure 2

Skeletal findings in mice treated with/without prednisone, following particle implantation on the cranial dome vs Sham surgery: Cortical bone volume (BV) at the calvaria in mm³ (A), cortical trabecular thickness (Tb.Th) (B), cortical surface (C) and number per HPF (high-power field) at the midline suture, and cortical osteoclast number (OC.Nr.) (D) in mice undergoing sham operation (Sham) or particle application (Particle) with (Prednisone) and without (Placebo) treatment with prednisone pellets are displayed (Mean $\pm$ SD). Further, spinal bone mineral density (BMD) (E), spinal bone volume fraction (VOX-BV/TV) (F), spinal trabecular thickness (G), spinal trabecular number (Tb.Nr.) (H) and spinal trabecular separation (Tb.Sp.) (I) are shown. 20 x = 20-fold magnification. ∗p < 0.05; ∗∗p < 0.01.

Figure 3

Histomorphometry. Histomorphometry (HE-staining) at the suture (calvaria) at 2.5x (upper row), 5.0x (middle row) and 20x (lower row) magnification displaying intact bone in placebo treated and Sham operated animal (A–B), eroded surface after particle application in a placebo treated animal (C–E), (H–I) intact bone in a prednisone treated and Sham operated animal (F–G) and eroded surface after particle application in a prednisone treated animal.