Evaluation of pre-osteoblastic cell line behaviors under low shear stress conditions†

The bone is a dynamic tissue that undergoes continuous remodeling through the activities of osteoclasts, osteoblasts, and osteocytes, influenced by mechanical stimuli via mechano-transduction. While relatively high shear stress levels (>1 Pa) have been extensively studied for their positive effects on pre-osteoblast and osteoblast cells' function, the influence of relatively low shear stress (<1 Pa) remains largely unexplored. This study investigates the effects of low shear stress (0.01 Pa and 0.1 Pa) on the pre-osteoblastic cell line's behaviors using a specially designed shear stress generating microchannel system. First of all, numerical analysis was conducted to optimize microchannel parameters for generating the desired shear stress levels, leading to the design of a microchannel that ensures sufficient internal volume for cell viability. The results from CCK-8 and ALP activity assays demonstrated that low shear stresses significantly enhanced pre-osteoblast proliferation while inhibiting differentiation to osteoblasts over time. Furthermore, immunofluorescence and SEM imaging revealed that pre-osteoblastic cell lines exposed to low shear stress exhibited a contracted morphology and increased alignment, suggesting that shear stress promotes proliferation by facilitating mitotic rounding. These findings underscore the importance of low shear stress in pre-osteoblast behavior, providing valuable insights for bone tissue engineering and regenerative medicine strategies aimed at mimicking physiological interstitial fluid flow.