The role of interleukin-1 on proteoglycan metabolism of rabbit annulus fibrosus cells cultured in vitro.

The effects of human recombinant interleukin-1 alpha (IL-1 alpha) on proteoglycan (PG) metabolism of rabbit intervertebral disc were investigated morphologically and biochemically using rabbit annulus fibrosus (AF) cells in culture. AF cells could maintain their differentiated phenotype well in our primary culturing condition. In this situation, IL-1 alpha stimulated the cells and induced marked increase of PG release. Dose dependency of IL-1 alpha on PG release was seen in the concentration range between 5-50 U/ml. Caseinolytic activity produced and secreted into the medium by AF cells was assayed and it was found that IL-1 alpha enhanced the enzyme activities in the medium. The effects of IL-1 alpha on PG and DNA synthesis were also studied. Slight depression was observed in PG synthesis but there was no effect on DNA synthesis. These data suggest that IL-1 alpha may play an important role in PG metabolism of intervertebral disc cells, especially in the catabolic pathway of PG.