Macrophage secretory products influence the survival of statoacoustic neurons

Prior studies have shown that macrophages are recruited to sites of injury or infection in the sensory organs of the inner ear, but the effects of macrophages and their cytokine secretory products on the sensory structures of the ear are not known. In the present study, cultures of dissociated statoacoustic neurons were incubated with selected macrophage secretary products and the numbers of surviving neurons after 48 h in vitro were quantified. Results indicate that two macrophage secretary products, interleukin 1 and fibroblast growth factor 2, can enhance the survival of statoacoustic neurons, while another cytokine, tumour necrosis factor-alpha can diminish the survival of those neurons. Also, numerous macrophages were present in both cytokine-treated and control cultures. The findings suggest that macrophages may influence the survival of the sensory neurons of the inner ear.