[Beta-actin changes during hair cell regeneration in the chick basilar papilla]

To investigate the changes of beta-actin and beta-actin mRNA expression during hair cell regeneration in the chick basilar papilla(BP) following gentamicin ototoxicity.

Thirty-six chicks were given muscular injection of gentamicin at dosage of 100 mg/kg.d for 10 consecutive days, and twelve additional chicks received injection of normal saline instead of gentamicin as controls. At 1, 3, 7, 14, 21 and 28 days after the treatment, six chicks in experimental group and two chicks in control group were sacrificed. Basilar papillas were prepared for immunohistochemistry and in situ hybridization study. beta-actin and beta-actin mRNA expression in the damaged region were histologically analyzed by computer image system.

beta-actin immunoreactivity of BP changed significantly after treatment with gentamicin. From the first day to the fourteenth day after gentamincin, beta-actin immunoreactivity turned positive gradually. It approximated the normal response level at the fourteenth day after treatment of gentamincin. Then increasing rate of beta-actin immunoreactivity positive response level slowed from the fourteenth day after the treatment. At seventh day after treatment, beta-actin mRNA expression in BP increased to peak value, which preceded the peak expression of beta-actin in the regenerated hair cells.

Nascent hair cells seem to mature 14 days after hair cell damage, which may play a role in auditory functional recovery.