Mapping the Response of Human Osteocytes in Native Matrix to Mechanical Loading Using RNA Sequencing.

Area of Science:

• Bone Biology
• Mechanobiology
• Molecular Biology

Background:

• Osteocytes, the most abundant bone cells, are crucial for bone's mechanical adaptation by sensing loads and initiating chemical responses.
• Their embedded location within the mineralized matrix limits in vivo study, necessitating advanced in vitro models.
• A novel 3D mechanical loading model for human osteocytes in their native matrix was recently developed.

Purpose of the Study:

• To identify genes differentially expressed in human primary osteocytes within their native matrix following mechanical loading.
• To map the mechanoresponsive gene expression profile using RNA sequencing.
• To investigate the role of specific genes, such as RNF213, in bone mechanical adaptation.

Main Methods:

• Human fibular cortical bone explants from 10 donors were subjected to mechanical loading (2000 or 8000 μɛ) or no load.
• Explants were cultured for 0, 6, or 24 hours post-loading.
• RNA sequencing was performed for differential gene expression analysis, with validation by real-time PCR.

Main Results:

• Mechanical loading resulted in 28 differentially expressed genes at 6 hours and 19 genes at 24 hours post-culture.
• Eleven genes related to bone metabolism were identified, including EGR1, FAF1, H3F3B, PAN2, RNF213, SAMD4A, TBC1D24, EGFEM1P, HOXD4, SNORD91B, and SNX9.
• RNF213 gene expression was significantly decreased by mechanical loading, confirmed by real-time PCR.

Conclusions:

• Mechanically loaded osteocytes exhibit differential expression of 47 genes, with 11 linked to bone metabolism.
• Decreased RNF213 expression suggests a potential role in bone mechanical adaptation, possibly through regulating angiogenesis.
• Further investigation is required to elucidate the functional significance of these differentially expressed genes in bone mechanotransduction.