An improved method of transducing retinal ganglion cells using AAV via transpupillary injection in adult mouse eyes

Intravitreal injection of adeno-associated virus (AAV) vectors is a good approach for transducing retinal ganglion cells (RGCs) in mice. It allows for high transduction efficiency and is relatively specific to RGCs. To deliver vectors, most studies use a transscleral approach that can have potentially negative effects, causing damage to the lens or retina. We optimized the intravitreal injection method using a transpupillary approach to minimize ocular damage and efficiently transfect RGCs.

C57BL/6J mice were anesthetized, and their irises were dilated. The eyeball was held with forceps while a small, full-thickness incision was made halfway between the center and periphery of the cornea. Using a bent 35-gauge blunt needle, the tip was navigated through the incision across the anterior chamber to reach the distal aspect of the pupil. The needle was inserted through the pupil, swept around the lens, and entered the vitreous, delivering expression vectors containing cytomegalovirus (CMV) promoter-driving green fluorescent protein (AAV-CMV-GFP) into the vitreous chamber. Fourteen days after injection, live fluorescent fundus images were taken, followed by immunostaining for GFP.

With the improved injection technique, the lens remained clear and undamaged. Fundus imaging and GFP staining showed that over 90% of the mouse retinas sustained no visible damage. Retinas injected via the transpupillary approach also exhibited GFP transduction throughout the ganglion cell layer.

Transpupillary intravitreal injection reduces the potential risk compared to the transscleral approach, offering a promising and efficient method for delivering reporter genes to RGCs and ensuring high levels of gene expression without damage to the lens or retina.