Shh signaling mediates complete retina regeneration through the activation of stem/progenitor cells located in the ciliary margin

FIORE, LUCIANO; SANCHEZ, VIVIANA; OLMOS CARREÑO, CINDY; TERUEL, LUISA R; SCICOLONE, GABRIEL; DI NAPOLI, JENNIFER; MEDORI, MARA; DEL RIO-TSONIS, KATIA

San Diego

Congreso; Neuroscience 2016; 2016

Society for Neuroscience

Retina regeneration in the embryonic chick can occur through two distinct pathways: 1) by retinal pigmented epithelium (RPE) transdifferentiation or 2) by the activation of stem/progenitor cells located in the ciliary margin (CM). In chicks, retina regeneration is only possible during the fourth day of development (E4) and when it is stimulated by growth factors. Fibroblast growth factor 2 (FGF2) stimulates transdifferentiation and activation of stem/progenitor cells from the CM, whereas sonic hedgehog (Shh) induces activation of stem/progenitor cells from the CM. RPE transdifferentiation produces an inverted retina without RPE, whereas regeneration from the CM produces a normally oriented and laminated retina. Obtaining this last form of regeneration is the goal of any regenerative strategy.The central aim of this work was to evaluate which treatment presented the highest efficacy to produce a complete retina along all its tangential extension. The Shh pathway and its analog activator SAG were evaluated for their potential to induce complete retina regeneration from the stem/progenitor cells of the CM.After retinal removal at E4, we tested different treatments to evaluate retinal regeneration: FGF2 and RCAS-Shh or SAG alone or in combination with FGF2 were added to induce retinal regeneration.We showed that the activation of the canonical Shh pathway induced by SAG produced the highest efficacy of complete retinal regeneration through the activation of stem/progenitor cells of the CM (100% of embryos) in vivo. We also showed that the retinal ganglion cells (RGCs) from this regenerated retina have positional information, as they expressed the Eph/ephrin system in a gradient similar to the retinas during development.These results increase the probability of obtaining an efferent system that establishes a topographic order of connections in the tectum.Retina stem/progenitor cells exist in other species, including humans. Thus, our findings provide insights on how retinal stem cells can be activated for possible regenerative therapies.