Abstract
Purpose To characterize the spectral-domain optical coherence tomography (SD-OCT) findings of the rhodopsin S334ter transgenic rats (line 4) in relation to the morphologic and electroretinographic features. Materials and Methods Rhodopsin S334ter transgenic rats (line 4) were employed as a model of retinal degeneration. The Sprague-Dawley (SD) rats were used as a wild-type control. SD-OCT (Micron IV®; Phoenix Research Labs, Pleasanton, CA, USA) was performed on the S334ter rats (line 4) from postnatal days (P) 13−110. The longitudinal changes of the SD-OCT images were analyzed both qualitatively and quantitatively in comparison to those of SD rats. The SD-OCT images were also compared to the histological and electron microscopic findings from examination performed on P 22, 36, and 61. Full field combined rod and cone electroretinography (ERG) was performed and the relationship between the thickness of the retinal sublayers and the amplitudes of the a- and b-waves was further analyzed. Results The photoreceptor inner and outer segment layer became diffusely hyperreflective in the SD-OCT images of the S334ter rats; these findings were not observed in the SD rats. This hyperreflective change corresponded to the degenerated inner and outer segments and the accumulation of the extracellular vesicles in the interphotoreceptor matrix. Quantitatively, the retinal outer sublayer and the photoreceptor sublayer in the S334ter rats became progressively thinner in comparison to those in the SD rats; the difference was statistically significant. The amplitudes of both the a- and b-waves on ERG were severely deteriorated in the S334ter rats. Discussion The SD-OCT images in the S334ter rats noninvasively provided information regarding the pathological changes in the photoreceptors and the longitudinal changes of both qualitative and quantitative changes during retinal degeneration in the S334ter rats (line 4). The pathological features of the photoreceptor inner and outer segments can be detected on SD-OCT as diffuse hyperreflective changes in the photoreceptor layer.
Highlights
Retinitis pigmentosa (RP) is the most common hereditary condition to cause retinal degeneration; it occurs in approximately 1 in 4,000 people worldwide [1]
We characterized the spectral-domain optical coherence tomography (SD-OCT) findings observed during the processes of retinal degeneration in rhodopsin S334ter transgenic rats in relation to the histological, ultrastructural, and ERG features
The SD-OCT findings related to retinal degeneration in rhodopsin P23H transgenic rats were previously reported [8, 10, 11], there have been no reports on retinal degeneration in S334ter rats except for the time domain OCT (TD-OCT) findings of S334ter rats [16]
Summary
Retinitis pigmentosa (RP) is the most common hereditary condition to cause retinal degeneration; it occurs in approximately 1 in 4,000 people worldwide [1]. We previously reported the characteristic SD-OCT findings of retinal degeneration in Royal College of Surgeon’s (RCS) rats with mertk gene mutations [7] and the rhodopsin P23H (line 2) transgenic rats [8]. Because the mechanisms of cell death are highly heterogeneous and depend on the causative mutations [15], it is important to investigate the characteristics of photoreceptor degeneration associated with each causative gene mutation. We attempted to characterize the SDOCT findings of retinal degeneration in transgenic rhodopsin S334ter rats (line 4) [17], a typical Class 1 mutant, to seek any particular characteristics in the OCT findings in relation to the morphological and electrophysiological features
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