Data for Differential Gene Expression in Trabecular Bone Osteocytes is Related to the Local Strain and Strain Gradient

Osteocytes regulate the response of osteoclasts and osteoblasts to mechanical loading by differentially expressing signaling molecules through post-translational modification, degradation, and gene transcription. The magnitude and mode of bone tissue deformation that elicits a transcriptional response in osteocytes in situ has been difficult to quantify. We measured SOST, Wnt11, TNF, and FRZB gene expression in osteocytes using RNAScope^® and compared the local tissue level strain and strain gradient – which we used as an indicator of potential poroelastic fluid flow – in the tissue surrounding osteocytes with high vs. low gene expression. On average, the measured expression of all four genes differed between loaded and unloaded explants, with the mean SOST expression level decreasing by 45%. In the loaded explants, gene expression was altered from baseline in about 30% of the osteocytes, and they were surrounded by tissue with higher strain and strain gradient than the 20 to 25% of osteocytes that remained near baseline expression. Both deviatoric strain and dilatational strain gradient were sensitive and specific predictors of the mechanobiological response for individual genes as well as combinations. SOST expression was highly related to strain gradient, providing evidence that osteocytes respond to fluid flow in the lacuna-canalicular system.