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.