Up-regulation of matrix metalloprotease-9 in middle ear cholesteatoma - correlations with growth factor expression in vivo?

The role of matrix metalloproteases and their regulation in the pathology o f middle ear cholesteatoma is still unclear. Recently we have demonstrated that incubation of keratinocytes with cholesteatoma debris and granulation tissue extracts causes induction of gelatinase B (matrix metalloproteinase- 9, MMP-9) secretion in vitro. Antibodies against a variety of growth factor s revealed some inhibitory effect on MMP-9 induction, caused by debris or g ranulation tissue extracts. In order to investigate the coherence of growth factor expression and matrix metalloproteinase activity in vivo in middle ear cholesteatoma, we performed quantitative gelatin zymographic analysis w ith tissue homogenates of 37 cholesteatoma and nine external ear canal skin (EACS) samples. Furthermore we quantified levels of the cytokines IL-1 alp ha, IL-1 beta, TNF-alpha, TGF-beta and EGF present in tissue extracts, usin g enzyme-linked immunosorbent assays (ELISA), and correlated cytokine conce ntrations with gelatinolytic activities. Zymographic analysis revealed a hi ghly heterogeneous expression of gelatinase A and B in cholesteatoma specim ens. As shown previously, MMP-9, but not MMP-2, was increased in cholesteat oma when compared to EACS samples. ELISA studies revealed a significantly e levated IL-1 alpha level in cholesteatoma. Regression analysis involving ge latinolytic activity and cytokine concentrations in tissue homogenates show ed no statistically significant correlation between expression of gelatinas es and the cytokines IL1-alpha, IL1-beta, TNF-alpha, TGF-beta or EGF. The d iscrepancy between in vitro observations and the situation in vivo is discu ssed critically.