Keratinocyte growth factor and its receptor expression in chronic otitis media with and without cholesteatoma

Chronic suppurative otitis media (CSOM) with and without cholesteatoma is regarded as chronic inflammation of the middle ear and mastoid mucosa that can be associated with the presence of granulation tissue and infection, which can lead to ossicular damage and hearing loss, but it is commonly known that cholesteatoma behaves aggressively. Both lesions appear to contain a predominant population of inflammatory cells, among which proinflammatory cytokines secreting keratinocyte growth factor (KGF) and its receptor (KGFR). No clear difference was demonstrated between these entities. The purpose of this study was to investigate the potential influence of KGF and KGFR in increased epithelial-cell proliferation of chronic otitis media (COM) with cholesteatoma in contrast to COM without cholesteatoma (CSOM), particularly in the granulative form, and to compare the rate of proliferation activity of epithelial cells using the Ki-67 epithelial proliferation marker expression.

We analyzed 105 ears with cholesteatoma vs. 53 ears with CSOM without cholesteatoma using our KGF and KGFR variables, and the ratio of proliferating epithelial cells using Ki-67. The percentage of the specimens expressing KGF and KGFR was compared between the two groups for statistical significance using the Pearson's chi-square test. Immunohistochemical staining was conducted and the proportion of the cells staining positive for the nuclear antigen Ki-67 was evaluated in a quantitative and visual way, using light microscopes.

KGF was positive in 88.57% of cholesteatoma and was positive in 41.51% CSOM without cholesteatoma specimens (cholesteatoma vs. CSOM, p=0.001). The positive rate of KGFR in the CSOM group was 33.96% compared to those in cholesteatoma, which was 60.95%. Compared to the cholesteatoma specimens, a significantly smaller number of Ki-67 labeling index was detected in CSOM specimens.

Our results indicated that the abnormal behavior of the cholesteatoma epithelium seems to be induced by the paracrine interaction between KGF and KGFR. Furthermore, we found that cholesteatoma expressing both KGF and KGFR had high Ki-67 index, which correlated with its aggressiveness. These findings suggest that excessive KGF and KGFR synthesis may contribute to the hyperproliferative state in cholesteatoma and could explain the pathological difference between cholesteatoma and CSOM.