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Alendronate reduces adhesion of human osteoclast-like cells to bone and bone protein-coated surfaces
S Colucci1, V Minielli, G Zambonin
1Istituto di Anatomia Umana Normale P.zza G. Cesare, 70124 Bari, Italy.
Abstract:
Bisphosphonates (BPs) are potent inhibitors of bone resorption and are therapeutically effective in disease of increased bone turnover, but their mechanism(s) of action remain to be elucidated. Using as experimental model human osteoclast-like cell lines derived from giant cell tumors of bone, extensively characterized for their osteoclast features, we investigated the adhesive properties of osteoclasts on bone slices and on different proteins of the extracellular matrix in the presence of BPs. Adhesion assays using bone slices pretreated with ALN, at the established active concentration, showed that, although the morphology of osteoclasts plated onto pretreated bone slices was not modified, the number of adherent cells was reduced by the treatment of about 50% vs. controls. The effect of ALN on the adhesion of osteoclast-like cells onto specific extracellular matrix proteins, such as bone sialoprotein-derived peptide, containing the RGD sequence, conjugated to BSA (BSP-BSA) and fibronectin (FN), was also tested. In the case of FN the treatment with ALN of protein-coated wells did not modify the percentage of cell adhesion compared with the control, whereas onto BSP-BSA the presence of ALN significantly reduced adhesion of about 40-45%, suggesting that the inhibitory effect of ALN on cell adhesion could probably be due to the interference with receptors specifically recognizing bone matrix proteins as alphaVbeta3 integrins. Furthermore, ALN induced Ca-mediated intracellular signals in osteoclasts, triggering a 2-fold increase in intracellular calcium concentration.
Insights
Bisphosphonates (BPs) inhibit osteoclast adhesion to bone matrix proteins like BSP-BSA, potentially via alphaVbeta3 integrins. Alendronate (ALN) also increases intracellular calcium in osteoclasts.
Area of Science:
- Bone Biology
- Pharmacology
- Cell Biology
Background:
- Bisphosphonates (BPs) are effective in treating bone diseases by inhibiting bone resorption.
- The precise mechanisms of action for BPs, particularly their effects on osteoclast function, require further elucidation.
- Osteoclast activity is crucial for bone turnover and is a target for therapeutic intervention.
Purpose of the Study:
- To investigate the effects of bisphosphonates (BPs) on osteoclast adhesion to bone and extracellular matrix proteins.
- To explore the potential role of specific matrix proteins and cell surface receptors in BP-mediated effects.
- To examine the impact of BPs on intracellular signaling pathways within osteoclasts.
Main Methods:
- Utilized human osteoclast-like cell lines derived from giant cell tumors of bone.
- Performed adhesion assays using bone slices and extracellular matrix proteins (BSP-BSA, fibronectin) treated with alendronate (ALN).
- Measured intracellular calcium concentration changes in osteoclasts following ALN treatment.
Main Results:
- Alendronate (ALN) significantly reduced osteoclast adhesion to bone slices by approximately 50%.
- ALN treatment decreased osteoclast adhesion to bone sialoprotein-BSA (BSP-BSA) by 40-45% but did not affect adhesion to fibronectin.
- ALN induced a two-fold increase in intracellular calcium concentration in osteoclasts, mediated by calcium signaling.
Conclusions:
- Bisphosphonates, exemplified by ALN, interfere with osteoclast adhesion to specific bone matrix proteins, suggesting interaction with receptors like alphaVbeta3 integrins.
- The findings indicate that BPs may exert their anti-resorptive effects not only by inhibiting bone resorption but also by modulating osteoclast adhesion and intracellular signaling.
- Understanding these mechanisms provides insights into the therapeutic efficacy of BPs in bone diseases characterized by increased bone turnover.