Connexin 26 Immunohistochemistry in Temporal Bones With Cochlear Otosclerosis

Hypothesis: Connexin-26 (Cx26) expression is diminished in the spiral ligament of subjects with hearing loss and cochlear otosclerosis (CO). Background: Human temporal bone (HTB) studies have demonstrated that CO is associated with hyalinization of the spiral ligament. We hypothesize that hyalinization is associated with a loss of fibrocytes with a consequent decline in Cx26 expression. Cx26 and Connexin-30 (Cx30) encode gap junction proteins expressed in supporting cells of the organ of Corti, the spiral limbus, stria vascularis, and in fibrocytes of the spiral ligament. These gap junctions are critical for potassium recycling and maintenance of the endocochlear potential. Diminished expression of these proteins would likely be associated with hearing dysfunction. Methods: Histopathology and clinical characteristics of 45 HTB specimens with CO and spiral ligament hyalinization were reviewed. Those with sensorineural or mixed hearing loss but normal or near-normal hair cell counts were analyzed with light microscopy, and Cx26-immunoreactive (IR) signal was qualitatively assessed. Results: H&E staining demonstrated hyalinization in the spiral ligament and loss of type II and type III fibrocytes. Cx26-IR was diminished throughout the cochlea affected with CO compared with normal controls. Conclusions: Cx26-IR reduction in the spiral ligament of subjects with CO likely plays a role in hearing loss.