CHARACTERIZATION OF CYTOPLASM-FILLED PROCESSES IN CELLS OF THE INTERVERTEBRAL DISC

We examined cells from the nucleus pulposus and annulus fibrosus of ad ult bovine intervertebral discs; using confocal laser scanning microsc opy on living unfixed tissue. These cells were visualised using chloro methyl fluorescein diacetate, a membrane-impermeant fluorescent dye. T he organisation of cells from the outer annulus was also determined us ing confocal microscopy after fixation and staining the actin-filament s with FITC-phalloidin. We found that cellular processes were a domina nt feature of cells from all regions of the disc including the cells o f the nucleus pulposus and inner annulus. These processes were also vi sible in histological sections of disc examined both at the light and electron microscope level, even though cells from the nucleus and inne r annulus appeared chondrocyte-like, being rounded and enclosed in a c apsule. The function of these processes is at present unknown. We sugg est that they may serve to sense mechanical strain.