The EDA-deficient mouse has Zymbal's gland hypoplasia and acute otitis externa

In mice, rats, dogs and humans the growth and function of sebaceous glands and eyelid Meibomian glands depend on the ectodysplasin signalling pathway. Mutation of genes encoding the ligand EDA, its transmembrane receptor EDAR, and the intracellular signal transducer EDARADD leads to Hypohidrotic Ectodermal Dysplasia characterised by impaired development of teeth and hair as well as cutaneous glands. The rodent ear canal has a large auditory sebaceous gland, the Zymbal’s gland, whose function in the health of the ear canal and tympanic membrane has not been determined. We report that the EDA deficient Tabby (EdaTa) mouse, the EDAR deficient mouse (EdarOVE1B/OVE1B) and the EDARADD deficient sparse and wavy hair rat (Edaraddswh/swh) have Zymbal’s gland hypoplasia. EdaTa mice also have ear canal hypotrichosis and a 25% prevalence of otitis externa at P21. Treatment with agonist anti-EDAR antibodies rescues Zymbal’s glands and ear canal pilosebaceous units. The aetiopathogenesis of otitis externa involves infection with Gram-positive cocci and dosing pregnant and lactating EdaTa females and pups with Enrofloxacin reduces the prevalence of otitis externa. We infer the deficit of sebum is the principal factor in predisposition to bacterial infection and the EdaTa mouse is a potentially useful microbial challenge model for human acute otitis externa, commonly known as swimmer’s ear.