Up‐Regulation of MUC5AC and MUC5B Mucin Genes in Nasopharyngeal Respiratory Mucosa and Selective Up‐Regulation of MUC5B in Middle Ear in Pediatric Otitis Media with Effusion

Abstract Objectives: Mucins are the major component responsible for the gel‐like properties of mucus secretion. Currently, little is known about the regulation of mucins in otitis media with effusion (OME). We investigated the expression of MUC5AC and MUC5B mucin gene messenger (m)RNAs in middle ear effusions as well as in tissue biopsies of the respiratory mucosa of the nasopharynx by means of reverse‐transcription polymerase chain reaction (RT‐PCR). Study Design: A prospective, controlled, clinical trial. Methods: The study group consisted of 25 children with a diagnosis of OME who were to undergo bilateral ventilation tube insertion with adenoidectomy. A sample of middle ear effusion (n = 50) as well as tissue biopsy from nasopharyngeal respiratory mucosa (n = 25) were obtained from each patient. For the nasopharyngeal mucosal biopsies, two control groups were made up from 30 children with healthy ears who underwent tonsillectomy ± adenoidectomy operation; control A, 15 children with adenoid hypertrophy, and control B, 15 children with healthy nasopharynx. RNAs were extracted from effusion and tissue samples, and semiquantitative RT‐PCR was performed for MUC5AC and MUC5B to investigate their expression. Results: In the middle ear effusions, MUC5B mRNA expression was detected in 48 (96%), whereas MUC5AC mRNA was detected in 8 (16%). On semiquantitative analysis, MUC5AC/glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) and MUC5B/GAPDH mRNA ratios in the study group were significantly increased compared with those in both control groups ( P < .05). Conclusions: The results suggest that the middle ear has a unique mucin gene expression pattern when compared with that of the nasopharynx. Up‐regulation of MUC5B in the ear may play an important role in the pathogenesis of middle ear effusions.