A Three-Dimensional Mechanical Loading Model of Human Osteocytes in Their Native Matrix

Area of Science:

• Biomedical Engineering
• Skeletal Biology
• Mechanobiology

Background:

• Osteocytes, crucial mechanosensory cells in bone, regulate bone adaptation via signaling to osteoblasts and osteoclasts.
• Their function is influenced by the native bone matrix, but in vitro models are lacking.
• Understanding osteocyte mechanosensing is vital for bone health research.

Purpose of the Study:

• To develop an in vitro three-dimensional (3D) mechanical loading model for human osteocytes within their native matrix.
• To assess osteocyte viability, sclerostin expression, and microdamage under mechanical loading.
• To provide a tool for investigating osteocyte mechanoresponsiveness in various bone conditions.

Main Methods:

• Human cortical bone explants with embedded osteocytes were cultured.
• A custom apparatus applied three-point bending mechanical loading (sinusoidal displacement).
• Osteocyte viability, sclerostin expression, and microdamage were assessed via histology, micro-CT, and BaSO4 staining post-loading.

Main Results:

• A linear relationship was established between loading magnitude (2302–13,811 µɛ) and applied force (1.6–4.9 N).
• Osteocyte viability remained unaffected by 1600 µɛ loading at 24 hours post-load.
• Sclerostin expression and bone microdamage were not significantly altered by loading up to 8000 µɛ.

Conclusions:

• A novel in vitro 3D mechanical loading model for human osteocytes in their native matrix was successfully developed.
• The model maintains osteocyte viability and can be used to study mechanoresponsiveness.
• This model is suitable for investigating the impact of altered bone matrix composition in metabolic bone diseases on osteocyte function.