Moderate Fluid Shear Stress Could Regulate the Cytoskeleton of Nucleus Pulposus and Surrounding Inflammatory Mediators by Activating the FAK-MEK5-ERK5-cFos-AP1 Signaling Pathway

Figure 1

(a) The structure and function of intervertebral disc: compressive stress (C) produced hydrostatic pressure (P) in nucleus pulposus, then transferred the stress to the fibrous ring, and induced formation of tensile stress (T) in the fibrous ring tissue, induced counterforce of nucleus pulposus by fibrous ring (Z). (b) The proteoglycan was wrapped in a network of collagen fibers (the coarse line of the peripheral zebra). Proteoglycan was composed of a central chain (part of the dotted line) formed by hyaluronic acid. The clustered proteoglycan composed of the core protein (red line) and the glucan sulfate (solid line) was attached to the central chain. (c) Proteoglycan was hydrophilic swelling until pressure balanced with the tensile tension in the collagen fibers, the compress stress on the disc would squeeze part of the water out of the disc, then increased concentration of proteoglycan and increased potential energy of expansion inhibited further compression of nucleus pulposus. Once the compress stress was disappeared, the water returned to the tissue, the new balance was achieved, and the formation of fluid shear stress happened. (d) The blue arrow repressed proteoglycan, and the red arrow repressed collagen fiber. (g) Schematic diagram of fluid shear force device.

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