MUC5AC expression in human middle ear epithelium of patients with otitis media

Abstract

Objective: To compare levels of middle ear (ME) MUC5AC expression in patients with otitis media (OM) with patients without OM. Mucin gene 5AC has been identified as a major secretory mucin in the ME and is fundamentally important in the development of ME mucoid effusions, hearing loss and also provides ME mucosal protection and bacterial clearance.

Design: Case control.

Setting: Tertiary, academic, pediatric otolaryngology practice.

Patients: Patients 9 months to 7 years old undergoing routine tympanostomy tube (TT) insertion for recurrent otitis media (RecOM) or chronic otitis media with effusion (COME) were compared with control patients without a history of OM undergoing cochlear implantation.

Methods: During routine TT placement or cochlear implantation, a 1-mm biopsy sample of the ME epithelium was obtained. RNA was extracted, and real-time reverse transcriptase-polymerase chain reaction was used to quantify levels of MUC5AC expression.

Results: Twenty-three patients with OM (12 with RecOM and with 11 COME) were evaluated using 5 controls. Mean age was not different between groups. In the RecOM group, mean expression of MUC5AC was 25.92 times greater than in controls. In the COME group, the mean expression was 155.40 times greater than in controls.

Conclusions: Levels of MUC5AC expression in the human ME are significantly increased in patients with RecOM and COME compared with controls. This study demonstrates MUC5AC gene changes in patients with OM and highlights the need for greater understanding of the molecular responses in OM; particularly that of mucin. A thorough exploration of these factors will provide opportunities to develop novel interventions for the extremely common problem of OM.

Figure 1

MUC5AC was amplified from human middle ear mucosa biopsy. M: standard DNA marker, size in bp as marked on the left; lane 1: A 176 bp MUC5AC PCR fragment amplified from RecOM-50 sample; lane 2: NlaIII restriction digestion yielded correct product of 130 and 46 bp fragments.

Figure 2

MUC5AC transcript levels in middle ear mucosa from different study groups as measured by quantitative PCR. The error bar displayed is the standard error of the mean.

Figure 3

Middle ear fluids (MEF) from otitis media patients were examined for MUC5AC protein. Equal amount of total protein from each sample was assayed by indirect ELISA as described in methods. Protein extraction from gastric stomach served as a positive control. All MEF tested positive for MUC5AC.