Inflammatory Lesions of Cochlea in Murine Cytomegalovirus-Infected Mice with Hearing Loss

We sought to determine the distribution of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and lymphocytes in the cochlea of mice infected with murine cytomegalovirus (MCMV). For this purpose, 16 newborn mice were divided equally into model and control (uninfected) groups. In model group, 10 μl of MCMV was injected into the brain of each mouse whereas in control group, 10 μl of physiological saline was injected. Fourteen days after the injection of MCMV, the auditory brainstem response audiometry was performed. Later, the mice were killed and the acoustic capsule samples were collected for polymerase chain reaction analysis, histopathological and immunohistochemical studies. Compared with control mice, the incubation period was longer (F = 13.797; P = 0.003) and the amplitude was lower (F = 5.095; P = 0.043) in model group mice. It indicated that the intracerebral injection of MCMV caused hearing loss in mice. Histopathological examination of cochleas revealed increased levels of lymphocytic infiltration in the membrana vestibularis. Higher levels of TNF-α and IL-6 in scala tympani were detected by immunohistochemical staining. Taken together, the hearing loss in mice could be related with the inflammatory changes occurring in cochlea after inception of MCMV infection.