Modulating primary cilia and cilia-dependent Shh signaling increases retinal ganglion cell survival by repressing astrocyte reactivity after optic nerve injury.

The primary cilia and cilia-dependent signaling are key regulators of neurodegenerative diseases. However, their roles in glaucoma and optic nerve injury remain largely unexplored. Here, we reported that astrocyte primary cilia elongated after optic nerve injury, and genetic ablation or shortening of these cilia significantly increased retinal ganglion cell (RGC) survival. Furthermore, single-cell transcriptomic analysis identified astrocytes as the predominant cell type transducing Sonic hedgehog (Shh) signaling. Activation of canonical Shh signaling, which is transduced through primary cilium, downregulated the expression of reactive astrocyte markers, including glial fibrillary acidic protein (GFAP) and complement component 3 (C3). Using adeno-associated virus (AAV)-mediated gene delivery, we further demonstrated that activating astrocytic Shh signaling or shortening their primary cilia promoted RGC survival by suppressing astrocyte reactivity. Together, our findings reveal a critical role for primary cilia and cilia-dependent Shh signaling in modulating astrocyte reactivity to promote RGC survival after optic nerve injury.