Summary: Bright light retinal damage in rodents remains one of the most widely used models mimicking human retinal degenerations such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD).
Retinal damage induced by bright light in laboratory rodents has remained one of the most widely used models mimicking human retinal degenerations such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD) for more than five decades.
The model is induced by exposing rodents to bright light (2.500-10.000 lux). The BLE induces the apoptosis of photoreceptors and retinal pigment epithelium1-3. Previous studies have shown that the total retinal thickness decreases with aging, as seen in 7 vs 3.5 month-old mice. Moreover, the BLE exacerbates the retinal damage in aged mice when compared to young mice.
The purpose of this study was to determine whether age, or lifetime exposure to light, is the primary determinant of photoreceptor viability in the BLE model.
|Method of induction||Exposure to bright light|
|Follow-up period||Up to 7 days|
|Route of compound administration||Topical (e.g. eye drops), subretinal, intravitreal, systemic|
|Read-outs||1. In vivo imaging: spectral domain optical coherence tomography (SD-OCT),|
2. In vivo functional assessment
3. Morphological assessment,
4. Molecular biology (ELISA, Western blotting, qPCR)
Materials and Methods.
Animals. Young (3.5-month-old) and aged (7-month-old) BALB/c male mice were used in this experiment. Mice were divided into four groups, each group containing 15 mice.
• Group 1: raised in darkness until 3.5-months of age
• Group 2: raised in darkness until 7-months of age
• Group 3: raised in normal lighting conditions (12 h dark – 12 h light) until 3.5-months of age
• Group 4: raised in normal lighting conditions (12 h dark – 12 h light) until 7-months of age
Bright Light Exposure (BLE). Animals were exposed to BLE (10.000 lux) for 12 h.
Electroretinography The functional response of retinal cells was evaluated using flash electroretinography (fERG) (Celeris, Diagnosys LLC, MA, USA) at baseline and 7 days after BLE.
Spectral Domain Optical Coherence Tomography (SD-OCT). The total retinal thickness was measured using SD-OCT (Envisu R2200, Leica-microsystems, IL, USA) at baseline level and 7 days after BLE.
Histology One week after BLE the eyes were enucleated, embedded into paraffin and sectioned. The retinal sections were stained for hematoxylin and eosin (H&E) to verify the morphological differences between the groups
Older BALB/c mice are more susceptible to BLE than young BALB/c mice. However, mice raised in absolute darkness had thicker retina and stronger response to flash stimuli than similar age controlled animals. This indicates that both age and light have an impact on retinal viability in BALB/c mice.
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