Mapping the osteocytic cell response to fluid flow using RNA-Seq.

Area of Science:

• Biomedical Engineering
• Cell Biology
• Molecular Biology

Background:

• Bone adaptation to mechanical forces is mediated by osteocytes, specialized bone cells.
• Osteocytes sense mechanical stimuli like fluid shear stress, triggering signaling pathways that regulate bone turnover.
• Gene expression changes are crucial for these mechano-responsive signaling pathways.

Purpose of the Study:

• To investigate the utility of RNA sequencing (RNA-Seq) for characterizing mechano-responsive gene regulation in osteocytes.
• To compare RNA-Seq findings with previous gene microarray data in fluid-flow stimulated MLO-Y4 cells.
• To identify both known and novel fluid flow-sensitive gene transcripts in osteocytes.

Main Methods:

• MLO-Y4 osteocyte-like cells were subjected to oscillating fluid shear stress.
• RNA was extracted and analyzed using RNA sequencing (RNA-Seq).
• Gene expression data was compared with previous microarray analyses.

Main Results:

• RNA-Seq detected 55 fluid flow-regulated gene transcripts, similar in number to microarray analysis.
• RNA-Seq demonstrated a greater dynamic range, with more transcripts showing significant fold-changes.
• Novel flow-sensitive transcripts, including Ccl2, were identified, alongside known targets like Nos2 and Ptgs2.
• Inferred inflammatory responses and implicated HIF-1α and AMPK signaling pathways.

Conclusions:

• RNA-Seq provides a more comprehensive and dynamic characterization of the osteocyte transcriptome under mechanical stimulation than microarrays.
• This advanced technique enhances the understanding of signaling pathways involved in bone adaptation and mechanotransduction.
• The identification of novel flow-sensitive genes opens new avenues for research into bone cell biology.