Biological characterization of interleukin-1-like cytokine produced by cultured bone cells from newborn mouse calvaria.

We have investigated the role of interleukin-1 (IL-1) and IL-1-like factor in the regulatory mechanisms of a bone remodeling system. To determine whether the bone cell itself produces IL-1-like cytokine, we examined bone cells cultured from newborn mouse calvaria. Bone cells migrating from fragments of newborn mouse calvaria were used in this study. We also used bone cells obtained by consecutive digestion of the calvaria with enzymes. These bone cells were cultured in fetal calf serum-containing alpha-MEM. IL-1-like cytokine activity was measured by incorporation of [3H]thymidine into C3H/HeJ thymocytes stimulated with PHA. When treated with lipopolysaccharide (LPS) from Escherichia coli 0111 B4, the cultured bone cells produced a significant amount of IL-1-like cytokine. The maximum concentration of IL-1-like cytokine was observed in culture supernatants of the bone cells cultured for 24 hours with the LPS in serum-free medium. The IL-1-like cytokine closely resembles IL-1 in some of its biological characteristics: stimulation of mitogen-induced thymocyte proliferation, stimulation of fibroblast proliferation, pyrogenicity, and molecular weight. These results show that cultured bone cells from newborn mouse calvariae produce an IL-1-like cytokine that closely resembles IL-1.