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Platelet-activating factor stimulates resorption by rabbit osteoclasts in vitro
Z G Zheng1, D A Wood, S M Sims
1Division of Oral Biology, Faculty of Dentistry, University of Western Ontario, London, Canada.
The American Journal of Physiology
|January 1, 1993
Summary
Platelet-activating factor (PAF) increases osteoclast activity and bone resorption. This suggests PAF
Area of Science:
- Osteoimmunology
- Cellular Biology
- Biochemistry
Background:
- Platelet-activating factor (PAF) is a potent inflammatory mediator.
- Previous studies showed PAF elevates cytosolic free Ca2+ concentration ([Ca2+]i) in isolated rat osteoclasts.
Purpose of the Study:
- To investigate the effects of PAF on osteoclast function and resorptive activity.
- To determine the role of PAF in bone resorption.
Main Methods:
- Isolated neonatal rabbit osteoclasts were used.
- Cytosolic free Ca2+ concentration ([Ca2+]i) was monitored using microspectrofluorimetry.
- Osteoclast retraction and pseudopod dynamics were observed via time-lapse videomicroscopy.
- Resorptive activity was assessed by culturing osteoclasts on dentin slices.
Main Results:
- PAF (10-100 nM) caused a transient elevation of [Ca2+]i in 9 out of 16 osteoclasts.
- PAF induced a transient retraction of osteoclast pseudopods.
- PAF (200 nM) significantly increased both individual resorption pit area and total planar area resorbed on dentin slices.
- Calcitonin, used as a control, decreased resorptive activity.
Conclusions:
- PAF directly activates osteoclastic resorption.
- PAF may contribute to bone and mineralized cartilage resorption in inflammatory conditions like rheumatoid arthritis and periodontitis.