Effects of chymopapain on intervertebral disc and cartilage. (Ultrastructural study)

A direct ultrastructural study was carried out with a view to determining the changes brought about in vitro by chymopapain on the intervertebral disc and the vertebral growth plate. The tissues studied were: (A) fragments of protruded nucleus pulposus and extruded disc tissue; (B) portions of human and rabbit annulus fibrous; (C) fragments of rabbit vertebral growth plate. The fragments of tissue were incubated with chymopapain for three, six and twenty-four hours and were then fixed. In the protruded nucleus pulposus and extruded disc tissue, chymopapain produced disappearance of the electron-dense granules (which are presumably proteoglycans) and of the electron-dense granular material of the intercellular matrix. The enzyme probably also has an injurious action on the chondrocytes, but does not affect the fibrils and collagen fibres. Its action is also conditioned by the dimensions of the fragment of tissue incubated. If this is large, only the peripheral portion is completely digested. The action of the enzyme on the annulus fibrosus and the vertebral growth plate is similar to that on the nucleus pulposus. The present study indicates that the clinical effects of chymopapain are due to digestion of the proteoglycan granules and the electron-dense granular material of the herniated nucleus pulposus. These effects appear to be correlated with the collagen fibre content of the tissue, in the sense that the greater the collagen content, the more tissue mass remains unaffected.