Human B-defensin-1 mRNA is transcribed in tympanic membrane and adjacent auditory canal epithelium

The external auditory canal is less susceptible to infections than the sens itive middle-ear cavity, Since recent research has provided insight to the production of potent antimicrobial peptides from various surface epithelia, we wanted to investigate whether protection of the external auditory canal in part could be explained by the production of human beta-defensin-1 (HBD -1). This particular peptide is known to be constitutively expressed in var ious surface epithelia, such as airway, skin, and urogenital tissues. By re verse transcriptase PCR we demonstrate HBD-1 mRNA in the pars tensa and par s flaccida of the tympanic membrane and in the meatal skin. In situ hybridi zation studies localized the HBD-1 mRNA to the epidermal layer of these tis sues. The HBD-1 transcripts were also evident in the sebaceous glands and i n hair follicles of the meatal skin. In contrast, HBD-1 mRNA was not detect ed in the tympanal epithelium of the eardrum. The widespread presence of mR NA encoding for this broad-spectrum antimicrobial peptide in the meatal ski n and tympanic membrane suggests that HBD-1 participates in the innate anti microbial defense of the external auditory canal and middle-ear cavity.