Intervertebral disc cell mechanics and biological responses to load

Purpose of review: A review is presented on current knowledge of micromechanical factors in the intervertebral disc and their role in modifying cell biology and changes with degeneration. Recent findings: Evidence suggests that substantial biologic remodeling occurs in the intervertebral disc in response to mechanical stimuli, which may contribute to the health or degenerative state of the intervertebral disc. Important differences in cell morphology, mechanics, micromechanical factors, and mechanobiology are noted to occur between cells of the nucleus pulposus and anulus fibrosus. Changes in these features with degeneration are critically understudied, particularly degeneration-associated changes in cell morphology, cell mechanics, and altered physiology with mechanical loading. Summary: Information on the mechanisms that govern cell responses to mechanical stimuli in the intervertebral disc is just emerging. Studies must address determination of the factors that control micromechanical stimuli, but also mechanisms by which mechanics may interact with genetic factors to regulate expression and remodeling of extracellular matrix molecules, cytokines, and mediators of pain and inflammation in degenerating tissue.