A paradigm for skeletal strength homeostasis

Area of Science:

• Biomechanical Engineering
• Skeletal Biology
• Cellular Mechanotransduction

Background:

• Skeletal strength is crucial for mechanical function and is determined by mass, geometry, and fatigue.
• Bone cells possess sensor and effector systems to maintain skeletal strength homeostasis.
• Mechanical usage is perceived through deformation and fatigue, signaling cellular responses.

Purpose of the Study:

• To integrate engineering principles with skeletal biology to explain skeletal strength homeostasis.
• To elucidate the mechanisms by which bone cells sense and respond to mechanical loading.
• To describe the roles of modeling and remodeling in maintaining bone strength and integrity.

Main Methods:

• Analysis of skeletal strength determinants (mass, geometry, fatigue damage).
• Description of the bone lining cell-osteocyte complex as the mechanical sensor.
• Explanation of bone modeling and remodeling systems as effectors responding to cellular signals.

Main Results:

• Skeletal strength is actively regulated by bone cells in response to perceived mechanical usage.
• The osteocyte network detects deformation and fatigue, modulating bone cell activity.
• Modeling enhances bone geometry, while remodeling repairs fatigue damage, optimizing skeletal strength.

Conclusions:

• Bone cells dynamically maintain skeletal strength by sensing mechanical loads and initiating adaptive responses.
• Hormones and agents can alter cellular mechanosensing by changing cytoskeletal rigidity, mimicking disuse or hyperuse.
• Understanding these mechanisms is key to developing interventions for skeletal diseases.