Interleukin-1α-dependent regulation of matrix metalloproteinase-9 (MMP-9) secretion and activation in the epithelial cells of odontogenic jaw cysts

Interleukin-1 alpha (IL-1 alpha) and matrix metalloproteinase-9 (MMP-9) are thought to be involved in odontogenic cyst expansion. In this study, we investigated the effects of IL-1 alpha. on the secretion and activation of MMP-9 in odontogenic jaw cysts. An active form of MMP-9 was present in odontogenic keratocyst (6 of 8 cases) fluids more frequently than dentigerous cyst (3 of 10 cases) and radicular cyst (3 of 10 cases) fluids, although proMMP-9 was present in all cyst fluids. Odontogenic keratocyst fragments in explant culture secreted a larger amount of IL-1 alpha than dentigerous cyst and radicular cyst fragments in explant culture, and spontaneously secreted both proMMP-9 and an active form of MMP-9. The fragments of dentigerous cysts and radicular cysts secreted a small amount of proMMP-9, but no active form of MMP-9. Exogenously added recombinant human IL-1 alpha (rhIL-1 alpha) increased the secretion and activation of proMMP-9 in the fragments of dentigerous cysts and radicular cysts. The epithelial cells isolated from odontogenic keratocysts secreted IL-1 alpha and proMMP-9 without stimulation. Under the cultivation on a fibronectin-coated dish, rhIL-1 alpha increased the secretion of proMMP-9 from the epithelial cells in a dose-dependent manner. Moreover, rhIL-1 alpha induced the secretion of proMMP-3 and plasminogen activator urokinase (u-PA) from the epithelial cells, and converted the secreted proMMP-3 to the active form in the presence of plasminogen. The secreted proMMP-9 was also activated in the presence of rhIL-1 alpha and plasminogen. Hence, our results suggest that IL-1 alpha. may up-regulate not only proMMP-9 secretion but also proMMP-9 activation by inducing proMMP-3 and u-PA production in the cyst epithelial cells by autocrine/paracrine regulatory mechanisms.