TNF and cholesteatoma: Therefore, the assumption that MMP2 was expressed in cholesteatomas and the external auditory canal skin still had its worth; that fact that they were raising is that cholesteatomas stimulated by infectious factors produce more MMP2 than the external auditory canal skin, which was then proved by Wilmoth, Schultz and Antonelli, in 2003, who observed in an experimental study that tympanic membranes of lab animals (gerbils) placed in a culture with bacteria toxins (lipopolysaccharides and tumor necrosis alpha factor), expressed greater quantities of metalloproteinases.