Osteogenic protein-1 is most effective in stimulating nucleus pulposus and annulus fibrosus cells to repair their matrix after chondroitinase ABC-induced in vitro chemonucleolysis.

BACKGROUND CONTEXT: Chondroitinase ABC (C-ABC) is used in chemonucleolysis to degrade, with great specificity, the chondroitin sulfate and dermatan sulfate chains of proteoglycans (PGs). A recent study showed that osteogenic protein-1 (OP-1) is very effective in stimulating the production and formation of the extracellular matrix by rabbit intervertebral disc cells.
PURPOSE: To test the hypothesis that the repair of the extracellular matrix of the intervertebral disc after chemonucleolysis by C-ABC can be stimulated by exposure to a low dose of a growth factor, OP-1. STUDY
DESIGN: An alginate bead cell culture system was used to monitor the effects of OP-1 on the repair of damaged matrices after in vitro chemonucleolysis with C-ABC.
METHODS: Rabbit nucleus pulposus (NP) or annulus fibrosus (AF) cells cultured for 2 weeks in alginate gel were briefly exposed to low concentrations of C-ABC and then cultured in the presence or absence of OP-1. The control group was cultured without enzyme treatment for the same period in the absence of OP-1. At each time point, the contents of DNA and proteoglycan accumulation and proteoglycan synthesis were measured.
RESULTS: NP or AF cells cultured in alginate beads, which were digested with C-ABC and then treated with OP-1, recover PG content more rapidly than those cultured in the absence of OP-1. The major contributor to the superior matrix repair in the cells treated with OP-1 was an up-regulation of proteoglycan synthesis.
CONCLUSIONS: OP-1 was effective in stimulating matrix repair by NP and AF cells after their matrices were nearly totally depleted of sulfated glycosaminoglycans. The use of OP-1 after chemonucleolysis might help the disc to regain biomechanical strength, weakened by enzyme digestion, by stimulating matrix metabolism.