MMP9 and cholesteatoma: Therefore, the MMP expression levels were tested using Real-time PCR, and the results revealed that the expression levels of MMP-2 (p < 0.01), MMP-8 (p < 0.001) and MMP-9 (p < 0.01) were significantly increased in human acquired cholesteatoma (n = 10) compared with the normal skin (n = 10) (Fig. 4A–C).