Retinal Muller glial cells (RMG) have a primary role in maintaining the homeostasis of the retina. In pathological situations, RMG execute protective and regenerative effects, but can also contribute to neurodegeneration. Cultured primary RMG have recently been recognized to secrete pro-survival factors for retinal neurons for up to two weeks in culture, but this ability is lost when RMG are cultivated for longer durations. In our study, we investigated RMG supernatants for novel neuroprotective factors using a quantitative proteomic approach. Stable isotope labeling by amino acids in cell culture (SILAC) was used on primary porcine RMG. Supernatants of RMG cultivated for two weeks were compared to supernatants from cells which had already lost their protective capacity. Using this approach, we detected established neurotrophic factors such as transferrin, osteopontin (SPP1), and leukemia inhibitory factor (LIF), and identified C-X-C motif chemokine 10 (CXCL10) as a novel candidate neuroprotective factor. All factors prolonged photoreceptor survival in vitro. Ex-vivo treatment of retinal explants with LIF or CXCL10 demonstrated a neuroprotective effect on photoreceptors (PR). Western blots on CXCL10 and LIF stimulated explanted retina and PR lysates indicated activation of pro-survival Signal Transducer and Activator of Transcription (STAT) signaling and B-cell lymphoma (BCL) pathways. These findings suggest that CXCL10 contributes to the supportive potential of RMG towards retinal neurons.
