THE EFFECT OF SUBSTANCE-P ON PROLIFERATION AND PROTEOGLYCAN DEPOSITION OF CELLS DERIVED FROM RABBIT INTERVERTEBRAL DISC

Study Design. This study is an in vitro investigation of the effects o f substance P on intervertebral disc cell metabolism. Objectives. To d etermine whether the neuropeptide, substance P, affects cells isolated from the intervertebral disc. Summary of the Background Data. Nerve f ibers containing substance P are present in the anulus fibrosus and ma y be released from the nerve terminals as in other tissues. Substance P is mitogenic for a variety of immune and connective tissue cells, an d a fragment of the peptide affects the metabolism of articular chondr ocytes. Methods. Cells were isolated enzymically from the anulus fibro sus of intervertebral disc of 8-week-old rabbits. The effects of subst ance P and the C-terminal pentapeptide fragment SP7-11 on cell prolife ration and proteoglycan deposition were determined by crystal violet a nd Alcian blue staining, respectively. Results. Substance P (10(-11)-1 0(-7) mol/l) had a small stimulatory effect on disc cell proliferation . Proteoglycan deposition in the cell layer increased concomitantly. A greater proliferative effect was observed with substance P fragment 7 -11 or with the addition of the neutral endopeptidase inhibitor, phosp horamidon. Conclusions. Substance P has small mitogenic effects on rab bit intervertebral disc cells in vitro. Further investigation is requi red to establish whether this might have biologic relevance in relatio n to the maintenance or repair of the intervertebral disc.