Strontium ranelate promotes osteoblastic cell replication through at least two different mechanisms

Area of Science:

• Cell Biology
• Molecular Biology
• Pharmacology
• Biochemistry

Background:

• Osteoblastic cell replication is crucial for bone health and is influenced by various factors.
• Strontium ranelate is a treatment for osteoporosis, but its precise cellular and molecular mechanisms of action are not fully understood.
• The calcium-sensing receptor (CaSR) has been proposed as a target, but alternative pathways require investigation.

Purpose of the Study:

• To investigate the signaling pathways mediating osteoblastic cell replication induced by strontium ranelate.
• To compare the effects of strontium ranelate with calcium chloride (CaCl2) on cell proliferation and signaling.
• To identify specific molecular targets and mechanisms responsible for strontium ranelate's mitogenic effects.

Main Methods:

• Utilized preosteoblastic MC3T3-E1 and pluripotent mesenchymal C3H10T1/2 cell lines.
• Administered strontium ranelate and CaCl2, assessing cell number changes.
• Performed immunoblot analysis to detect activation of signaling proteins (ERK, PKC, PKD, p38).
• Employed specific inhibitors to functionally analyze signaling pathway involvement.

Main Results:

• Strontium ranelate, but not CaCl2, dose-dependently increased MC3T3-E1 cell number.
• Both strontium ranelate and CaCl2 affected C3H10T1/2 cell proliferation similarly.
• Strontium ranelate induced delayed activation of ERK, PKC, and PKD in MC3T3-E1 cells, unlike the rapid effect of CaCl2.
• In C3H10T1/2 cells, strontium ranelate triggered both rapid and delayed signaling, including p38 activation.
• PKC/PKD pathway inhibition blocked strontium ranelate-induced replication in MC3T3-E1 cells; p38 inhibition affected C3H10T1/2 cells.
• ERK pathway inhibition reduced basal replication but not strontium ranelate-induced responses in either cell type.

Conclusions:

• Strontium ranelate stimulates osteoblastic cell replication via at least two distinct mechanisms.
• One mechanism may involve direct interaction with CaSR, triggering signals like p38 in C3H10T1/2 cells.
• A second, potential mechanism involves the delayed activation of signaling pathways, suggesting autocrine growth factor release.