Learning Objectives:

Introduction: Middle ear cholesteatoma (MEC), accompanied by chronic inflammatory response is characterized by invasive growth and osteolytic activity.

Aim: Present the cellular and inflammatory pathways in the pathogenesis of cholesteatoma and adjacent tissues.

Material and methods: Congenital, acquired MEC (study groups) and retroauricular skin specimens (control group, CS) were investigated for markers of inflammation using various immunohistochemistry, Western Blot, cell culture and flow cytometry techniques. Studied markers included proliferation and apoptosis of keratinocytes (PCNA, Ki67, p53, p21, APO2.7), angiogenesis and inflammation (TGF-α), proteasomal degradation pathway (low-molecular mass polypeptide-7 subunit of the immunoproteasome (LMP7), and selected molecular signalling (the DNA-binding high-mobility box 1 (HMGB1) in the protein advanced glycation endproducts (RAGE) axis.

Results: The significantly more intense expression of LMP7 and p21-positive cells was seen in MEC. The LMP7(+) cells were observed in MEC matrix and perimatrix. There was no meaningful difference between congenital and acquired MEC with respect to p21 contrary to p53. A statistical significance was obtained for APO2.7-positive cells in MEC epithelium (43.23 ± 4.8%) as compared to CS (29.89 ± 6.2%).

More extensive positive immunohistochemical reaction with anti-TGF-alpha, Ki67 and PCNA was observed in MEC matrix and perimatrix compared with CS.

RAGE expression levels was present in all cholesteatoma tissues (strong in 86 %) vs skin 25% (weak) respectively (p <  0.0001).

Conclusion: Selected markers of apoptosis, proliferation, angiogenesis and inflammatory response are associated with cholesteatoma development. The co-expression of HMGB1 and RAGE in MEC may result in activation of the intracellular signaling pathways. This process may be responsible for faster accumulation of keratin debris, more invasive process, and affect the clinical course and the treatment outcome.