Hyaluronic Acid-Based Hydrogels Enable Rod Photoreceptor Survival and Maturation In Vitro through Activation of the mTOR Pathway

The culture of isolated photoreceptors in vitro has remained elusive in neuroscience. By using defi ned hyaluronic acid (HA) hydrogels, photoreceptor survival and maturation in vitro is dramatically increased, as evidenced by upregulation of outer segment markers at the RNA and protein levels. While substrate stiffness is known to be a key factor infl uencing cell survival in vitro, it is shown that isolated photoreceptors do not respond to modifi cations in hydrogel stiffness modifi cations but depend, instead, on HA for survival. While the molecular pathways that are induced by HA on photoreceptors are unknown, mTOR activation is identifi ed as the molecular mechanism underlying the pro-survival effect, and it is demonstrated that the canonical Wnt and RhoA pathways are intermediaries. This work establishes a valuable method for isolated photoreceptor culture in vitro, which will be useful in translational and basic retinal research. The pathways identifi ed herein may be useful targets in retinal degeneration.