Survival-enhancing of spiral ganglion cells under influence of olfactory ensheathing cells by direct cellular contact

The efficacy of cochlear implantation is primarily associated with the quantity and health of the remaining spiral ganglion cells (SGCs). Olfactory ensheathing cells (OECs) are capable of expressing a variety of growth factors and adhesion molecules, playing an important role in enhancing cellular survival. To investigate the effect of OECs on the survival of SGCs, co-cultures of OECs and SGCs were developed in this study. In addition, OECs conditioned medium (OEC-CM) was employed to culture SGCs in contrast with the co-cultures. OECs were identified immunocytochemically by low-affinity nerve growth factor receptor p75 (P75NTR) and glial fibrillary acidic protein (GFAP), while SGCs were stained with neuron-specific markerβIII-tubulin. SGCs survival was assessed in different conditions. To explore the underlying mechanism, growth factors, adhesion molecules and their receptors were investigate using RT-PCR. Our results indicate that the co-cultures of OECs and SGCs can be successfully established and that both OECs and OEC-CM promote SGCs survival in vitro. SGCs survival was most enhanced when co-cultured with OECs. Both Olfactory bulb (OB) and OECs were proved to express BMP-4 and NCAM while BMPR-1A and a7 integrin were also detected in cochlea and SGCs. In conclusion, our results suggest that enhancement in co-cultures is in part due to direct cellular contact. Transplantation of OECs may be a cell-based therapy for the application of neurotrophic factors to the inner ear.