CHEMONUCLEOLYSIS WITH HUMAN STROMELYSIN-1

Study Design. Immunohistologic analysis was performed on surgically re moved samples of herniated nucleus pulposus to examine the expression of stromelysin-1. We performed in vitro and in vivo experiments to det ermine whether recombinant human (rh) stromelysin-1 is capable of degr ading nucleus pulposus. Objective. To analyze the production of strome lysin-1 in various types of herniated nucleus pulposus, and to examine the effects of this recombinant protein on nucleus pulposus tissues. Summary of Background Data. The authors previously demonstrated a prog ressive decrease in herniated nucleus pulposus size in some of the tra nsligamentous and sequestration types of herniated nucleus pulposus us ing magnetic resonance imaging. An increased production of stromelysin -1, a cartilage proteoglycan degrading enzyme, in herniated nucleus pu lposus was reported recently. The authors speculated that if stromelys in-1 is involved in the degradation of herniated nucleus pulposus, str omelysin-1 itself may be used as a chemonucleolytic agent. Methods. Im munohistologic analysis using streptoavidin-biotin method was performe d on 20 herniated nucleus pulposus samples to investigate the expressi on of stromelysin-1. Five herniated nucleus pulposus samples were incu bated in a tissue culture medium in the presence or absence of rh stro melysin-1. After 24 hours of incubation, their weight changes were mea sured, and the loss of proteoglycan was assessed by Safranin O stainin g. Rat nucleus pulposus tissues were obtained from coccygeal intervert ebral discs, and autologous subcutaneous transplantation was performed . Rh stromelysin-1 was injected into the grafted materials, and the re duction in size was followed by two-dimensional measurements from the skin surface, using engineer's calipers. Results. Immunohistologic ana lysis demonstrated the production of stromelysin-1 in the granulation tissues of herniated nucleus pulposus. When stromelysin-1 was injected into the murine nucleus pulposus tissues, they reduced in size more r apidly than the control group. In addition, human herniated nucleus pu lposus materials obtained at surgery showed significant weight loss wh en treated with stromelysin-1 in an organ culture system. Safranin O s taining revealed extensive depletion of proteoglycan in these herniate d nucleus pulposus samples.Conclusions. Stromelysin-1 is a possible ke y enzyme in herniated nucleus pulposus resorption, and stromelysin-1 m ay be a good candidate for use in chemonucleolysis. Administration of human stromelysin-1 may physiologically facilitate the resorption proc ess of herniated nucleus pulposus, increase the healing rate, and decr ease complications after chemonucleolysis.