Strontium ranelate improving metabolic imbalance in oim mice of osteogenesis imperfecta: The dual mechanism / 第二军医大学学报

ABSTRACT

Objective: To explore the dual effects of strontium ranelate (SrR) on primary osteoblasts and osteoclasts using an osteogenesis imperfecta (OI) model oim mouse. Methods: The osteoblasts were obtained by digesting the calvaria of one-week-old homozygote oim/oim mice and wild type (wt/wt) mice with type I collagenase. The osteoclasts were obtained by inducing the bone marrow mononuclear cells derived from the long bone of oim/oim mice and wt/wt mice aged between five and seven weeks old. SrR with different concentrations (1 mmol/L and 10 mmol/L) was used to stimulate the cells. Quantitative real-time PCR (qRT-PCR) and Western blotting were used to quantify the expression of osteoblast differentiation-related genes (Runt-related transcription factor 2 [Runx2], alkaline phosphatase [ALP] and osteocalcin [OCN]), osteoclast differentiation-related genes (calcitonin receptor [Calcr], tartrate-resistant acid phosphatase [Trap] and cathepsin K [CTSK]), and osteoclast differentiation-related transcription factors (cellular oncogene fos [c-fos] and nuclear factor of activated T-cell c1 [NFATc1]). The osteoblast differentiation and mineralization were evaluated by ALP staining and alizarin red S staining. The osteoclastogenesis and resorption activity of the osteoclasts were evaluated by Trap staining and pit formation assay. The effect of SrR on cell viability of osteoblasts and osteoclasts was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results: qRT-PCR and Western blotting showed that the expression levels of Runx2, ALP, and OCN in oim/oim mice were significantly increased at mRNA and protein levels after stimulation with SrR in a dose-dependent manner (all P<0.05). In comparison, SrR caused significant decreases in Calcr, Trap, CTSK, c-fos, and NFATc1 expression (all P<0.05). ALP staining and alizarin red S staining demonstrated that SrR stimulation significantly increased osteoblast differentiation and mineralization of oim/oim mice (all P<0.05). Trap staining and pit formation assay showed that SrR significantly decreased the formation number of osteoclasts and inhibited the resorption activity of osteoclasts in oim/oim mice (all P<0.05). MTT assay showed that 1 mmol/L and 10 mmol/L SrR had no cell cytotoxicity on osteoblasts or osteoclasts of oim/oim mice. Conclusion: SrR can improve the imbalance of bone metabolism in OI model oim mouse, which might involve the increases in osteoblast differentiation and mineralization and decreases in formation and resorption of the osteoclasts.