Abstract
We report that the most common retinal ganglion cell type that remains after optic nerve transection is the M1 melanopsin ganglion cell. M1 ganglion cells are members of the intrinsically photosensitive retinal ganglion cell population that mediates non-image-forming vision, comprising ∼2.5% of all ganglion cells in the rat retina. In the present study, M1 ganglion cells comprised 1.7±1%, 28±14%, 55±13% and 82±8% of the surviving ganglion cells 7, 14, 21 and 60 days after optic nerve transection, respectively. Average M1 ganglion cell somal diameter and overall morphological appearance remained unchanged in non-injured and injured retinas, suggesting a lack of injury-induced degeneration. Average M1 dendritic field size increased at 7 and 60 days following optic nerve transection, while average dendritic field size remained similar in non-injured retinas and in retinas at 14 and 21 days after optic nerve transection. These findings demonstrate that M1 ganglion cells are more resistant to injury than other ganglion cell types following optic nerve injury, and provide an opportunity to develop pharmacological or genetic therapeutic approaches to mitigate ganglion cell death and save vision following optic nerve injury.
Highlights
Retinal, optic nerve and brain injury may lead to vision loss by compression or trauma to retinal ganglion cell (RGC) axons that often lead to RGC death
We have found that M1 ganglion cells are the most common ganglion cell type that remains in the retina 60 days following optic nerve axotomy, comprising 8268% of all surviving RGCs
RGCs remaining after axotomy were identified by RBPMS immunoreactivity (Fig. 1a), a selective marker of mammalian RGCs that is primarily expressed in the cell body [8,9] and neurofilament-M (NF, Fig. 1b, arrows), a general marker of large and small RGCs [10,11,12,13,14]
Summary
Optic nerve and brain injury may lead to vision loss by compression or trauma to retinal ganglion cell (RGC) axons that often lead to RGC death. A small percentage of RGCs survive up to one year following axotomy [5,6,7]. The goal of these studies is to identify and characterize the RGCs that survive after optic nerve transection (ONT), and to determine whether they are representative of all RGC types or a subpopulation of RGCs in the rat retina. Knowledge of surviving RGC type morphology and neurochemistry may provide insights into intrinsic RGC protective features that mediate cell survival. These properties could provide the basis for the development of neuroprotective interventions to save vision
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