Effect of CX3CR1 Deficiency on Cochlear Macrophage Function and Age-Related Hearing Loss

Macrophages are recruited to areas of inflammation and degeneration, making them a vital topic concerning the degenerative cochlear disease, presbycusis. The cochlear lateral wall is a major place of inflammation; therefore, it provides sections to study macrophages in differing levels of degeneration. This project examined differences in macrophage numbers between young and aged samples and their three cochlear turns. The fractalkine macrophage receptor protein CX3CR1 also affects cochlear macrophages by recruiting them to these areas of degeneration. In addition to studying changes with age, this project also studied differences in regular, C57BL-6J, samples and CX3CR1 deficient samples. All samples were stained for fluorescence and imaged. These samples, consisting of the three cochlear turns, went through a blind quantification to determine changes in macrophage numbers with age and with a deficiency of CX3CR1. The C57BL-6J samples had a significant increase in macrophage numbers of the cochlear basal turn between the young and aged, while the CX3CR1 deficient samples did not have any significant changes. Comparing the aged samples of the C57BL-6J and CX3CR1 deficient cochlear turns, a significant increase was noted in the cochlear middle turn between the regular samples and the CX3CR1 deficient samples. These results suggest that the CX3CR1 protein may not be essential to the recruitment of macrophages to the cochlear lateral wall. This data and others like it is essential to understanding the cellular pathology underlying presbycusis, and that knowledge is vital in the development of potential therapies and treatments of this disease