• S Kubo, N Tajima, N Katunuma, K Fukuda, and H Kuroki.
• Department of Orthopaedic Surgery, Miyazaki Medical College, Japan.
• Spine. 1999 Jan 15; 24 (2): 120-7.

Study DesignInvestigation of the effects of recombinant human cathepsin L on intervertebral discs and comparison with the effects of chymopapain.ObjectiveTo evaluate the effects of cathepsin L on intervertebral discs as an agent for chemonucleolysis.Summary Background DataCathepsin L is a typical cysteine proteinase that belongs to the papain superfamily. It plays a major role in intracellular proteolysis and is not believed to induce anaphylactic reactions.MethodsIn vivo: Rabbit intervertebral discs were injected with recombinant human cathepsin L, its buffer solution, and chymopapain. After 1, 4, and 16 weeks the animals were killed, and radiologic and histologic examinations were performed. In vitro: The enzymatic actions of recombinant human cathepsin L and chymopapain on human intervertebral disc proteoglycans were examined immunohistochemically using antiproteoglycan antibodies.ResultsIn rabbit models, roentgenography showed that disc spaces treated with cathepsin L and chymopapain had become narrower 1 week after injection. Histologically, loss of safranin-O staining was observed in the anulus fibrosus of discs treated with cathepsin L. After 16 weeks, nucleus pulposus had regenerated with chondrocyte-like cells, and the safranin-O staining characteristics of the matrix also had recovered. In an immunohistochemical study, all components of the proteoglycan stained weakly after chymopapain digestion. After cathepsin L digestion, unsulfated chondroitin and core protein staining was weaker, but the chondroitin 6-sulfate staining was unaffected.ConclusionsCathepsin L seems to be an effective agent for chemonucleolysis. Its enzymatic action on proteoglycan appears to be different from that of chymopapain.

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