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Monoclonal antibodies against osteoclasts inhibit bone resorption in vitro
T J Chambers1, K Fuller, J A Darby
1Department of Histopathology, St Georges Hospital Medical School, London, England.
Abstract:
Several recently-derived monoclonal antibodies (mcabs) that bind with a high degree of specificity to membrane antigens of osteoclasts were tested for their effects on the function of giant cells from osteoclastomas. None of the antibodies stimulated bone resorption when incubated with giant cells on bone slices, nor did we find any evidence that the mcabs were able to block calcitonin-inhibition of bone resorption. However, three of the mcabs strongly inhibited bone resorption. This inhibition was unaccompanied by impaired survival or morphological evidence of toxicity, but the same mcabs induced a state of cytoplasmic quiescence we have previously found to be characteristic of the response of osteoclasts to local and systemic inhibitors of osteoclastic bone resorption. These results suggest that the mcabs bind to antigens of functional importance in bone resorption or its regulation, and the similarity between the response of giant cells to mcabs and hormonal inhibitors of bone resorption raises the possibility that the mcabs may bind to and cause activation of surface receptors for one or more of these hormones. Whether this is so or not, the mcabs which influence giant cell function may represent valuable probes for an analysis of the mechanism and regulation of osteoclastic bone resorption.
Insights
Monoclonal antibodies (mcabs) targeting osteoclast membrane antigens were investigated. Three mcabs significantly inhibited bone resorption in giant cells, suggesting potential roles in regulating this process.
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Osteoclasts are crucial for bone resorption.
- Osteoclastomas involve giant cells with osteoclast-like functions.
- Monoclonal antibodies (mcabs) offer specific targeting capabilities.
Purpose of the Study:
- To evaluate the functional effects of novel monoclonal antibodies (mcabs) on osteoclastoma giant cells.
- To determine if these mcabs can modulate bone resorption activity.
- To explore potential mechanisms of action for mcabs influencing osteoclast function.
Main Methods:
- Incubation of osteoclastoma giant cells with mcabs on bone slices.
- Assessment of bone resorption activity.
- Evaluation of cell survival, morphology, and cytoplasmic state.
- Comparison with hormonal inhibitors of bone resorption.
Main Results:
- No mcabs stimulated bone resorption.
- Three mcabs significantly inhibited bone resorption without causing toxicity.
- Inhibited mcabs induced a quiescent cytoplasmic state, similar to hormonal inhibitor responses.
- No evidence of blocking calcitonin-induced inhibition of bone resorption.
Conclusions:
- Specific mcabs can inhibit osteoclastic bone resorption by targeting functional membrane antigens.
- The observed inhibition mechanism may involve interaction with surface receptors, potentially mimicking hormonal regulation.
- These mcabs are valuable tools for studying the mechanisms and regulation of osteoclastic bone resorption.