Growth hormone increases interleukin-6 produced by human osteoblast-like cells

Physiological levels of GH are necessary for normal bone remodeling. GH treatment increases bone resorption and results in enhanced bone formation. The aim of the present study was to investigate whether the GH-induced increase in bone resorption could be mediated by a regulation of interleukin-6 (IL-6) production by human osteoblast-like cells. Cultures of human osteoblast-like cells were established from trabecular bone. Ribonuclease protection analysis demonstrated a high expression of the IL-6 messenger ribonucleic acid (mRNA) transcript in osteoblast-like cells, bone, and muscle, whereas expression was lower in liver. GH increased IL-6 mRNA levels as well as IL-6 protein released into the culture medium from human osteoblast-like cells in a time- and dose-dependent manner, with a maximal effect at 100 micrograms/L (mRNA, 322 +/- 95% of control; protein, 576 +/- 155% of control). In conclusion, GH increases IL-6 produced by human osteoblast-like cells. This in vitro evidence suggests, for the first time, a mechanistic paradigm by which GH modulates bone resorption.