11-cis-retinal and Hyperoxia

Retinopathy of prematurity (ROP) is a severe complication of premature infants, leading to vision loss when untreated. Presently, the molecular mechanisms underlying ROP are still far from being clearly understood. This study sought to investigate whether thyroid hormone (TH) signaling contributes to the neuropathology of ROP using the mouse model of ROP to evaluate longitudinal photoreceptor function.. Animals were exposed to hyperoxia from P7 to P12 to induce retinopathy, thereafter the animals were returned to room air (normoxia). The thyroid-activating enzyme type 2 deiodinases (Dio2) knockout (KO) mice and the littermate controls that were exposed to hyperoxia or maintained in room air and were then analyzed. The retinal function was evaluated using electroretinograms (ERGs) at three and seven weeks followed by histologic assessments with neuronal markers to detect cellular changes in the retina. Rhodopsin protein levels were measured to validate the results obtained from the immunofluorescence analyses.. In the ROP group, the photoreceptor ERG responses are considerably lower both in the control and the Dio2 KO animals at P23 compared to the non-ROP group. In agreement with the ERG responses, loss of Dio2 results in mislocalized cone nuclei, and abnormal rod bipolar cell dendrites extending into the outer nuclear layer. The retinal function is compromised in the adult Dio2 KO animals, although the cellular changes are less severe. Despite the reduction in scotopic a-wave amplitudes, rhodopsin levels are similar in the adult mice, across all genotypes irrespective of exposure to hyperoxia.. Using the mouse model of ROP, we show that loss of Dio2 exacerbates the effects of hyperoxia-induced retinal deficits that persist in the adults. Our data suggest that aberrant Dio2/TH signaling is an important factor in the pathophysiology of the visual dysfunction observed in the oxygen-induced retinopathy model of ROP.

Topics: Animals; Animals, Newborn; Blotting, Western; Disease Models, Animal; Electroretinography; Enzyme Activators; Hyperoxia; Immunohistochemistry; Iodide Peroxidase; Iodothyronine Deiodinase Type II; Mice; Mice, Knockout; Mice, Transgenic; Oxygen; Photoreceptor Cells, Vertebrate; Retinopathy of Prematurity; Rhodopsin; Thyroid Gland

There are no effective treatments for inherited retinal degenerations, which are prevalent causes of visual disability. Several proteins promote the survival of various types of neurons, and increasing expression of one or more of these survival factors is a promising strategy for a new treatment. Studies examining the effects of intravitreous injections of brain-derived neurotrophic factor (BDNF) in models of inherited retinal degenerations have suggested that BDNF has little survival-promoting activity for photoreceptors. In this study, we generated double transgenic mice with doxycycline-inducible expression of BDNF in the retina. In a model of primary rod photoreceptor degeneration, expression of BDNF resulted in significant delay in photoreceptor cell death and maintenance of retinal function assessed by electroretinogram recordings. Expression of BDNF also caused strong protection of photoreceptors from oxidative damage-induced cell death. These data suggest that continuous expression of BDNF, unlike intravitreous injections, results in morphologic and functional benefit in animal models of inherited retinal degeneration. Double transgenic mice with inducible expression of survival factors provide valuable tools for selection of survival factor candidates for gene therapy.

Topics: Animals; Brain-Derived Neurotrophic Factor; Cell Death; Cell Survival; Disease Models, Animal; Doxycycline; Gene Expression Regulation; Gene Transfer Techniques; Hyperoxia; Immunohistochemistry; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Nerve Growth Factors; Oxygen; Photoreceptor Cells; Rats; Retina; Retinal Degeneration; Rhodopsin; RNA, Messenger

Fibroblast growth factor-2 (FGF2) has neurotrophic effects in vitro and in vivo. It has been demonstrated to decrease photoreceptor cell death in rats exposed to constant light and in rats with an inherited defect in retinal pigmented epithelium (RPE) phagocytosis, but the effects of intravitreous injections of FGF2 in mice are equivocal. In this study, we used transgenic mice with increased expression of FGF2 in photoreceptors (rhodopsin promoter/FGF2 transgenics) to investigate the effects of sustained increased expression of FGF2 in mice with various types of photoreceptor degeneration, including rd mice that are homozygous for mutated phosphodiesterase beta subunit, Q344ter mice that undergo photoreceptor degeneration because of expression of mutated rhodopsin, and mice exposed to 75% oxygen for 1 or 2 weeks. At P21, the outer nuclear layer was markedly reduced in rd mice or Q344ter mice regardless of whether they inherited the rhodopsin promoter/FGF2 transgene. However, after 2 weeks of exposure to 75% oxygen, outer nuclear layer thickness was significantly reduced in littermate control mice compared to FGF2 transgenic mice (P = 0.0001). These data indicate that increased expression of FGF2 in photoreceptors protects them from hyperoxia-induced damage, but does not decrease cell death related to expression of mutated proteins involved in the phototransduction pathway. This suggests that FGF2 protects photoreceptors from oxidative damage, which may play a role in complex genetic diseases such as age-related macular degeneration.

Topics: Aging; Animals; Animals, Newborn; Cell Death; Fibroblast Growth Factor 2; Humans; Hyperoxia; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Photoreceptor Cells, Vertebrate; Reference Values; Retinal Degeneration; Rhodopsin; RNA, Messenger

Retinal astrocytes are located in the nerve fiber layer and along retinal blood vessels and have been hypothesized to participate in the induction and maintenance of the blood-retinal barrier. Platelet-derived growth factor-A (PDGF-A) is normally produced by retinal ganglion cells and is involved in astrocyte recruitment and proliferation. We used gain-of-function transgenic mice that express PDGF-A in photoreceptors to explore the roles of PDGF-A and astrocytes in the retina. Transgene-positive mice developed glial infiltration of the inner retina and had significantly less oxygen-induced retinal vascular closure and no neovascularization compared with littermate controls, which had prominent vascular closure and neovascularization. The increased survival of endothelial cells in transgenic mice in the face of oxygen-induced down-regulation of vascular endothelial growth factor was accompanied by an increase in astrocyte-derived fibroblast growth factor-2. Therefore, PDGF-A increases retinal astrocytes, which promote the survival of endothelial cells as well as their expression of barrier characteristics.

Topics: Animals; Capillaries; Cell Survival; Endothelial Growth Factors; Endothelium, Vascular; Fibroblast Growth Factor 2; Gliosis; Hyperoxia; Ischemia; Lymphokines; Mice; Mice, Transgenic; Neovascularization, Pathologic; Oxygen; Phenotype; Platelet-Derived Growth Factor; Retina; Retinal Vessels; Rhodopsin; RNA, Messenger; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors