Amyloid beta peptide is elevated in osteoporotic bone tissues and enhances osteoclast function

作者：Li, Shangfu; Liu, Bin; Zhang, Liangming; Rong, Limin^*

来源：Bone, 2014, 61: 164-175.

DOI：10.1016/j.bone.2014.01.010

• Osteoporosis
• Amyloid beta peptide
• Amyloid precursor protein
• Bone mineral density
• Osteocyte
• Osteoclast

Purpose: Epidemiological studies show that patients with Alzheimer's disease (AD) have an increased risk of developing osteoporotic hip fracture. However, whether abnormal amyloid beta peptide (A beta) deposition, one of the pathological hallmarks of AD, also occurs in osteoporosis and the relationship between A beta and human osteoporosis remain unknown. This study addressed these issues. @@@ Methods: Forty-five female patients (osteoporosis 21, osteopenia 16 and normal 8) with osteoporotic/traumatic vertebral compression fractures were enrolled and A beta 42 and amyloid precursor protein (APP) levels assessed in the biopsy specimens of vertebral trabecular bone using immunohistochemistry (IHC) staining and semi-quantitative evaluation assays. Spearman rank correlation analysis was applied to explore the association between A beta 42/APP levels and the corresponding bone mineral density (BMD). Moreover, immunofluorescent assays and laser scanning confocal microscopy assays were used to examine the expression patterns of A beta 42/APP in patient bone tissues and osteocytes. Additionally, eight female patients with osteoporotic/traumatic femoral neck fractures, including two control patients were selected and A beta 42 and APP were identified in the femoral necks by RT-PCR and Western blotting (WB) assays. Next, a rat model of ovariectomy-induced osteoporosis was created and we evaluated A beta 42 and APP expression differences in the proximal tibia by IHC and RT-PCR and WB assays in comparison with a sham-operation group. Finally, the RAW264.7 cell line and human bone marrow monocyte (hBMMC) derived osteoclasts and human A beta 42 co-culture assays were performed to investigate the effect of A beta 42 on osteoclasts cell viability, number, differentiation and activation by the Cell Counting Kit-8 assay, tartrate resistant acid phosphatase staining assay, RT-PCR assay measuring the lyric gene expression and hydroxyapatite resorption assay respectively. @@@ Results: The mRNA and protein expression levels of A beta 42 and APP were elevated remarkably in the osteoporotic bone tissues both from human and ovariectomized rats when compared with the age-/sex-matched controls. Moreover, the expression levels had a negative correlation with corresponding BMD in patients (R-A beta 42 = -0.617, p < 0.0001; R-App = -0.531, p = 0.0002). In addition, A beta 42 was located mainly in the membrane and cytoplasm of osteocytes and in the extracellular matrix, while APP was largely located in the membrane of the osteocytes. Finally, A beta 42 can potently enhance osteoclasts differentiation and activation but had no effect on osteoclasts cell viability or number (dose- and time-dependency did not exist and oligomerization of A beta 42 was not a prerequisite in the osteoclastogenesis assay). @@@ Conclusions: A beta is relevant to human osteoporosis and may have an important role in the pathogenesis of osteoporosis.

• 出版日期2014-4
• 单位中山大学