Objective: The shape of articular chondrocytes regulates their function, changes in response to mechanical load and is altered in osteoarthritis. We aimed to identify the shape of intervertebral disc cells in pathological and normal tissue.

Design: Immunohistology of human intervertebral discs using cytoskeletal markers to examine disc cell shape.

Subjects: Intervertebral discs from patients with degeneration (n=3), scoliosis (n=3), spondylolisthesis (n=3) and from non-pathological cadaveric spines (n=3).

Outcome measures: (i). Cell shape and (ii). Organisation/ content of cytoskeleton.

Results: In degenerate and normal discs, cells of the anulus fibrosus were generally elongated and bipolar, whilst those of the nucleus pulposus were rounded/oval. However, in localised areas, cells were observed with multiple cytoplasmic processes that extended into the discal matrix. In central regions of scoliotic and, most markedly, spondylolisthetic discs, such cells were more frequent. Their processes were vimentin positive (but F-actin negative) and reached up to 80μm in length. F-actin was clearly present in endothelial cells of blood vessels but absent in disc cells. In contrast, vimentin was expressed by disc cells within the discs’ inner regions, but not towards the outer anulus fibrosus.

Conclusions: The altered shape of disc cells in pathological tissue may reflect areas of abnormal loading. These changes are also likely to affect/reflect altered cell function and therefore have a role to play in the pathological process.