Dose-dependent effects of strontium on osteoblast function and mineralization

Area of Science:

• Biochemistry
• Cell Biology
• Pharmacology

Background:

• Strontium-ranelate is used for osteoporosis in elderly patients with reduced renal function, increasing risk of strontium accumulation.
• Previous studies in chronic renal failure (CRF) rats showed a dose-related multiphasic effect of strontium (Sr) on bone formation.
• An in vitro model using primary rat osteoblast cultures was employed to confirm in vivo findings.

Purpose of the Study:

• To investigate the in vitro effects of various strontium concentrations on primary rat osteoblast cultures.
• To confirm the dose-dependent multiphasic effects of strontium on bone formation and mineralization.

Main Methods:

• Primary rat osteoblast cultures were exposed to strontium (Sr) at concentrations ranging from 0 to 100 microg/mL.
• Assessed calcium incorporation, alkaline phosphatase activity, nodule formation, and mRNA synthesis of osteoblast-specific genes via RT-PCR.

Main Results:

• Low Sr doses (0.5-1 microg/mL) reduced nodule formation, indicating impaired osteoblast differentiation.
• Normal nodule formation and mineralization occurred at 2-5 microg/mL Sr.
• High Sr doses (20-100 microg/mL) reduced mineralization, suggesting interference with hydroxyapatite formation.
• Alkaline phosphatase activity and calcium incorporation mirrored nodule formation and mineralization patterns, respectively.
• RT-PCR revealed strontium's interference with osteoblast mRNA synthesis.

Conclusions:

• The in vitro model confirmed the multiphasic effect of strontium (Sr) on bone formation observed in CRF rat models.
• Low Sr concentrations affect bone formation by interfering with osteoblast differentiation.
• High Sr concentrations interfere with hydroxyapatite formation through physicochemical interactions.