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Cortical osteoclasts are less sensitive to etidronate than trabecular osteoclasts
D Chappard1, M Petitjean, C Alexandre
1LBTO-Laboratoire de Biologie du Tissu Osseux, Faculté de Médecine, Saint Etienne, France.
Summary
Bed rest increases bone resorption, particularly in trabecular bone. Etidronate therapy effectively reduced trabecular osteoclasts but did not affect cortical osteoclasts or bone mass.
Area of Science:
- Bone biology
- Osteoporosis research
- Pharmacology
Background:
- Spinal cord injury and prolonged bed rest can lead to acute osteoporosis.
- This bone loss is linked to increased osteoclastic resorption, particularly in trabecular bone.
- Bisphosphonates are known for their potent anti-resorptive properties.
Purpose of the Study:
- To investigate the effects of etidronate therapy on bone changes during a 120-day bed rest period.
- To compare the impact of etidronate on cortical versus trabecular bone osteoclasts.
- To assess etidronate's influence on cortical bone mass parameters.
Main Methods:
- 15 healthy subjects underwent a 120-day bed rest period, with some receiving etidronate therapy.
- Transiliac bone biopsies were taken before and after bed rest.
- Cortical thickness, porosity, and osteoclast counts (trabecular and cortical) were analyzed histochemically.
Main Results:
- Bed rest alone did not significantly alter cortical thickness, porosity, or osteoclast numbers.
- Etidronate treatment did not affect cortical bone mass parameters or cortical osteoclast numbers.
- Untreated subjects showed a significant increase in trabecular osteoclasts (+95.2%), while etidronate-treated subjects showed a significant decrease (-78%).
Conclusions:
- Bone cells exhibit heterogeneous responses based on their location (trabecular vs. cortical).
- Etidronate therapy is effective in reducing osteoclast activity in trabecular bone during bed rest.
- Cortical osteoclasts appear unresponsive to etidronate therapy under these conditions.