Adenosine triphosphate‐induced photoreceptor death and retinal remodeling in rats

Abstract

Many common causes of blindness involve the death of retinal photoreceptors, followed by progressive inner retinal cell remodeling. For an inducible model of retinal degeneration to be useful, it must recapitulate these changes. Intravitreal administration of adenosine triphosphate (ATP) has recently been found to induce acute photoreceptor death. The aim of this study was to characterize the chronic effects of ATP on retinal integrity. Five-week-old, dark agouti rats were administered 50 mM ATP into the vitreous of one eye and saline into the other. Vision was assessed using the electroretinogram and optokinetic response and retinal morphology investigated via histology. ATP caused significant loss of visual function within 1 day and loss of 50% of the photoreceptors within 1 week. At 3 months, 80% of photoreceptor nuclei were lost, and total photoreceptor loss occurred by 6 months. The degeneration and remodeling were similar to those found in heritable retinal dystrophies and age-related macular degeneration and included inner retinal neuronal loss, migration, and formation of new synapses; Müller cell gliosis, migration, and scarring; blood vessel loss; and retinal pigment epithelium migration. In addition, extreme degeneration and remodeling events, such as neuronal and glial migration outside the neural retina and proliferative changes in glial cells, were observed. These extreme changes were also observed in the 2-year-old P23H rhodopsin transgenic rat model of retinitis pigmentosa. This ATP-induced model of retinal degeneration may provide a valuable tool for developing pharmaceutical therapies or for testing electronic implants aimed at restoring vision. J. Comp. Neurol. 522:2928–2950, 2014. © 2014 Wiley Periodicals, Inc.

Stimulation of a Suprachoroidal Retinal Prosthesis Drives Cortical Responses in a Feline Model of Retinal Degeneration

“…Retinal ganglion cells appeared well conserved. These features are consistent with mid-to-late stage remodeling events reported in ATPinjected cat and rat retinae 24 and other models of retinal degeneration. 7,64,65 When local variations in retinal layer thickness, gliosis, and ganglion cell density were correlated with individual electrode thresholds in the implanted degenerate and control retinas, retinal ganglion cell count and GFAP expression were found to correlate with cortical threshold in the ATP-injected eyes.…”

“…All four animals were a subset of a larger cohort (n ¼ 19) required for another study 22 Unilateral retinal degeneration was induced in all four animals by using a single intravitreal injection of ATP at a concentration of 11 mM at the retina as previously described. 22,24,25 We have previously found that ATP injection induces a global retinal degeneration with a variable pattern of photoreceptor loss, where the most severely affected inner retina occurs in regions containing fewer residual photoreceptor nuclei. 22,23 Briefly, the procedure was performed under anesthesia induced through a subcutaneous injection of ketamine (20 mg/kg; Ilium Ketamil; Troy Laboratories Pty.…”

“…Immunohistochemical techniques followed methodology previously described. 22,24 After fixation and sectioning, slides were defrosted and washed in PBS. Sections were incubated overnight at room temperature in antibody buffer (3% normal goat serum, 1% bovine serum albumin, 0.5% Triton-X in PBS) containing 2 or 3 primary antibodies (listed below).…”

Glia–neuron interactions in the mammalian retina

“…Extracellular ATP acts as a ligand to purinergic receptors and P2X4 purinergic receptors (ionotropic receptors) are distributed in different cell types within the retina (bipolar cell terminals, horizontal cell somata and processes, calretinin-positive amacrine cells…etc), microglia, Müller cells and astrocytes. These receptors influence glia function and local tissue homeostasis in both physiological and pathological conditions (Vessey et al, 2014).…”

Nanosecond Laser Treatment for Age-Related Macular Degeneration Does Not Induce Focal Vision Loss or New Vessel Growth in the Retina

“…The posterior eyecups (n ‡ 5 per experimental group) were fixed in 4% paraformaldehyde in 0.1 M phosphate buffer, pH 7.4 (PB) for 30 minutes and cryoprotected in graded sucrose (10%, 20%, 30%) in PB overnight. 33 For retinal wholemounts, the entire eyecup (retina/choroid/sclera) was processed for immunohistochemistry as described previously 32,34 and specifically below. For retinal sections, the eyecup was embedded in optimal cutting temperature (OCT) compound (Tissue-Tek; Sakura, Torrance, CA, USA), frozen at À208C, and sectioned transversely at 14 lm on a Microm HM550 cryostat (Thermo Scientific, Walldorf, Germany).…”