Retinal ganglion cells induce stem cell-derived neuroprotection via IL-12 to SCGF-β crosstalk.

BACKGROUND: Stem cell-derived secreted factors could protect neurons in neurodegenerative disease or after injury. The exact neuroprotective components in the secretome remain challenging to discover. Here we developed a cell-to-cell interaction model to identify a retinal ganglion cell (RGC)-protective factor derived from induced pluripotent stem cells (iPSCs). METHODS: Primary RGCs were co-cultured with iPSCs or treated with iPSC-conditioned media in vitro. Cell viability were assayed using live-cell staining, and culture supernatant were analyzed via multiplexed antibody-based assays and ELISA. In vivo tests were carried out under mouse optic nerve crush model and RGC transplantation study in rats. Paired t-tests were used for data analysis between two groups. RESULTS: RGC viability was significantly enhanced when iPSCs were first stimulated with RGC-derived supernatant before iPSC-conditioned medium was collected and added into RGC culture. A significant increase of stem cell growth factor-beta (SCGF-β) concentration was detected in the latter conditioned medium. SCGF-β enhanced RGC survival in vitro and in vivo, and RGC-derived interleukin-12(p70) (IL-12[p70]) promotes secretion of iPSC-derived SCGF-β. Downstream of this IL-12(p70)-to-SCGF-β axis, ngn2 was significantly upregulated, and was found both necessary and sufficient for RGC survival. CONCLUSION: This study addresses a longstanding question of how neurons and stem cells interact to promote neuroprotection, and define a novel molecular interaction pathway whereby RGC's secretion of IL-12(p70) enhances iPSCs' secretion of SCGF-β, and SCGF-β protects RGCs via upregulating ngn2, suggesting that neurons may call on stem cells for their own protection.