Histological analysis showing morphology of cells in the transition zone of the endplate and the nucleus pulposus.

MMA sections were stained with safranin O/fast green. Cells in the transition zone between the cartilaginous endplates (EP) and nucleus pulposus (NP) (separated by dotted black line) stayed as rounded chondrocyte-like cells (indicated by black arrows) as in hyaline cartilage in CC and CT groups. Some cells in the cartilaginous endplates of the CCT group stayed as chondrocyte-like cells whereas cells right after the endplates zone changed to cells with spindle-shaped nucleus and cell lacunae were lost (indicated by yellow circles). CC: cyclic compression, CT: cyclic torsion, CCT: combined compression torsion. N = 2.