Figure 2

Imageological results of animals in each group. As shown by the sagittal T2WIs at 24 weeks, the IVD at L7–S1 of one animal in the control group was classified as Pfirrmann grade I (red arrow). The structure of the disc is homogeneous with a bright hyperintense white signal intensity and a normal disc height. Similarly, the IVD at L7–S1 of one animal in the microgravity group was classified as grade II (red arrow). The structure of the disc is inhomogeneous with a hyperintense white signal. The distinction between the NP and AF is clear, and the disc height is normal, with or without horizontal gray bands. Grade III (red arrow) in the +Gz group: The structure of the disc is inhomogeneous with an intermediate gray signal intensity. The distinction between the NP and AF is unclear, and the disc height is normal or slightly decreased. Grade IV (red arrow) in the mixed group: The structure of the disc is inhomogeneous, with a hypointense dark gray signal intensity. The distinction between the NP and AF is lost, and the disc height is normal or moderately decreased. As shown by the axial T2WIs, spinal stenosis developed in all of the experimental groups, but not the control group.