Dark horse in osteocyte biology: Glycocalyx around the dendrites is critical for osteocyte mechanosensing.

Osteocytes are considered as the major mechanosensory cells of the bone tissue that control the bone remodeling process. Since osteocytes are buried inside mineralized matrix, they maintain a strong communication network with other cells. Long dendritic processes of the osteocytes act as communication cables, conveying mechanical signals to the neighboring osteocytes and the cells on the bone surface; like osteoblasts and osteoclasts. Gap junctions and hemichannels formed by Connexin (Cx) 43 are observed to be involved in responding to the mechanical stimulus and in communicating the mechano-responsive biochemical signals. The contrast in the arrangement of the osteocyte cell body and the dendrites raises an important question of how these parts of the osteocyte respond to mechanical stimulation. We addressed this issue in our recent report through the stimulation of either osteocyte cell body or dendrites and our findings suggest that the osteocyte dendritic processes are sensitive to mechanical stimulation in comparison to the cell body. Most importantly, we observed that the dendritic processes are capable of conveying the mechanical signals to the cell body. Our findings also suggested that the glycocalyx surrounding the dendrites is required for sensing and conveying the mechanical signals. Degradation of the glycocalyx also leads to poor integrin attachment, thereby, affecting dendritic stiffness. These results suggest that the osteocyte dendritic processes are highly responsive towards mechanical stimulation and the glycocalyx surrounding the dendrites is critical in transducing these mechanical signals.