MMP28 and intervertebral disk degenerative disorder: MMP28 was not induced, however, by exposure of cells to a number of other cytokines, including basic fibroblast growth factor, epidermal growth factor, granulocyte-macrophage colony-stimulating factor, hepatocyte growth factor, IFNγ, IL-1β (a proinflammatory cytokine also involved in disc degeneration), platelet-derived growth factor, transforming growth factor beta (TGFβ), vascular endothelial growth factor, or insulin-like growth factor 1.