Retinal ganglion cell (RGC) degeneration, leading to irreversible blindness in chronic optic neuropathies such as glaucoma, begins with dendritic shrinkage followed by axon degeneration. Although limited axon regeneration in the optic nerve is possible with a genetic deletion of PTEN/SOCS3 after optic nerve injury, the roles of PTEN/SOCS3 on dendritic preservation and regeneration remain unclear. This study investigated the effect of PTEN/SOCS3 genetic deletion on the structural integrity of RGC dendrites and axons in the retina following optic nerve crush. Using time lapse, in vivo confocal scanning laser ophthalmoscopy to serially image dendritic and axonal arborizations of RGCs over six months after injury, RGC dendrites and axons were only preserved in Thy-1-YFP/PTEN and Thy-1-YFP/PTENSOCS3 mice, and axons in the retina regenerated at a rate of 21.1  μm/day and 15.5  μm/day, respectively. By contrast, dendritic complexity significantly decreased in Thy-1-YFP-SOCS3 and control mice at a rate of 7.0%/day and 7.1%/day, respectively, and no axon regeneration in the retina was observed. RGC survival probability was higher in Thy-1-YFP/PTEN and Thy-1-YFP/PTENSOCS3 mice compared with Thy-1-YFP-SOCS3 and control mice. The differential responses between the transgenic mice demonstrate that although a genetic deletion of PTEN, SOCS3, or PTEN/SOCS3 is sufficient for RGC axon regeneration in the optic nerve, a deletion of PTEN, but not SOCS3, ameliorates RGC dendritic shrinkage after optic nerve crush. This shows that the signaling pathways involved in promoting axon regeneration do not equally contribute to the preservation of dendrites, which is crucial to the translational application of neuroregenerative therapeutic alternatives for visual restoration.
Copyright © 2020. Published by Elsevier Ltd.