动物造模,视网膜变性 z-bo 2020-09-09 369

　　Introduction: In non-clinical toxicity evaluation, the ocular side effects of chemicals and drugs are a rare safety issue; depending on the nature of the findings, these side effects may lead to the termination of the compound during the drug development process, or to regulate the use of chemicals/supplements To avoid being used in humans. The eye is usually examined by clinical examination and histopathology of rodent and non-rodent species to assess the possibility of ocular toxicity. A careful microscopic examination of the eye can reveal the presence of treatment-related lesions and provide information on the dose response and type of lesions. However, in long-term toxicity (≥6 months) or carcinogenicity studies in albinism rats and mice, spontaneous eye diseases, especially retinal degeneration, are relatively common. Retinal degeneration in rats and mice can occur from aging changes or secondary to various injuries, such as physical trauma, detachment, inflammation, infectious factors such as viruses, vascular disorders such as infarction, increased intraocular pressure, malnutrition or genetic factors. Retinal degeneration can also be a direct toxic effect of systemic or local administration. Spontaneous retinal degeneration of uncertain etiology also appeared in laboratory rats and mice. However, in long-term studies (≥6 months), spontaneous retinal degeneration seen in the vehicle control group in albino rodents is considered to be mildly related, although the age effect cannot be ruled out. When rats and mice, especially albino rats, are exposed to excessive ambient light, light-induced retinal degeneration can occur. In addition to light intensity, the development of light-induced retinal degeneration in albino rodents is also affected by wavelength, length of exposure, dark adaptation time, initial exposure age, retinal maturity, gender, environmental temperature and diet, including lack of nutrients such as vitamins, The influence of zinc and taurine. It is important to distinguish between retinal damage and retinal phototoxicity associated with the test article, or to determine the possible additive or synergistic effects between the test article and the ambient light that causes retinal degeneration. The key component of research on the causes of retinal degeneration includes the morphology of retinal damage. Generally speaking, direct damage to the retina by compounds tends to cause diffuse damage in the eye, rather than more extensive local damage to the retina. On the other hand, in rodents, retinal damage caused by light does not occur uniformly across the entire retina, at least in the early stages, but has a very specific topographical location. Along the vertical meridian of the eye, damage to the upper retina is more severe than that of the lower retina, and damage to the central retina is more severe than that of the surrounding retina. In addition, rats and mice can show an accidental aging change called peripheral retinal degeneration. Therefore, in long-term rodent research, in order to evaluate the mechanism of retinal degeneration, it is very important to determine the location of retinal degeneration. Regarding the location of retinal damage, toxic compounds that affect the retina can be subdivided into compounds that mainly affect photoreceptors or ganglion cells and compounds that affect pigment epithelium. In the case of light-induced retinal degeneration, the outer segment of photoreceptor cells degenerates first, and photoreceptor cells subsequently participate. We performed a retrospective microscopic evaluation of the retina to determine whether the retinal degeneration is due to the direct action of chemical substances or the increase in photo-induced retinal degeneration caused by chemical substances.

　　H&E stained sections of the eyes of control and administration animals were retrieved from the NTP archive. Check the sections of each animal's binocular retinal degeneration under a microscope. Initially, 50 animals per group were assigned to each study; however, some animals were excluded from the evaluation due to improper samples due to autolysis or early death after death. The severity of retinopathy is graded according to the degree of degradation on the third degree scale. When all the retinal layers are clear, the inner and outer segments of the photosensitive layer are extended, and the outer nuclear layer is intact, the eye is considered normal (grade 0). When the different layers of the retina remain different, the lesion is considered to be grade 1 (mild), but the thickness of the photosensitive layer and outer nuclear layer (about 1-3 rows of nuclei) is reduced. Grade 2 (moderate) lesions are characterized by loss of photoreceptors, loss of most of the outer nuclear layer and outer plexiform layer. Grade 3 (obvious) lesions severely damage the normal retinal structure, loss of normal retinal tissue, with or without residual inner nuclear layer and ganglion cells. Chronic light exposure is a common cause of retinal degeneration and usually has a unique topographical location, in which the supratemporal retina including the area around the optic disc is preferentially affected. During the anatomy and treatment process, the correct positioning of the eyeball is very important to assess the topography of the retinal injury. In conventional rodent toxicity or carcinogenicity studies, the spheres are dissected and processed regardless of orientation, so it is impossible to perform accurate topographic evaluation of temporal/nasal and upper/lower parts of retinopathy. However, valuable information about the localization/spread localization of retinopathy can still be generated. In order to evaluate the role of light in retinal degeneration, the topography of the lesion is evaluated as follows: the severity of the lesion is a diffuse localization level across the entire retina. When there is a significant difference in the level of the lesion on both sides of the optic disc, the hemispheric localization is recorded. When a significant difference in the grade of the lesion is observed near the optic disc, center positioning is performed. In addition, peripheral retinal evaluations were performed separately, because albino rats, especially F344 rats, often observed spontaneous peripheral retinal degeneration, 24 months of age. For positioning data, a trend test was used to assess the statistical significance of dose-related increases in central/hemispheric or diffuse positioning in animals with retinal degeneration.

　　Results: The historical control range of retinal degeneration, where the eye is the tissue required by the protocol, was 0-79% (male) and 0-56% (female) in the 2-year study of F344/N rats; 2 in B6C3F1 mice In the annual study, 0-4% (male), 0-2% (female); in the 3-month study, 0-10% (male), 0% (female). Three 2-year carcinogenicity studies have increased the frequency of dose-related retinal degeneration. All 3 studies were in F344/N rats, including the oral gavage study of kava extract (dose: 0, 0.1, 0.3, and 1 g/kg), the acrylamide drinking water study (dose: 0, 0.0875, 0.175) , 0.35 and 0.70mM) and white malachite green feed research (dose: 0, 91, 272, 543 ppm). In these studies, the position of the cage was rotated every two weeks to minimize the confounding effects of long-term exposure to the eyes. Statistical analysis of retrospective histological evaluations of the eyes from these three studies showed that the increase in the frequency of dosing-related retinal degeneration was statistically significant through a trend test. Compared with the control group, the frequency of retinal degeneration of the kava extract 0.3g/kg, 1.0g/kg group and 1.0g/kg group was significantly increased in a dose-dependent manner. There were no significant differences between males and females in the average severity grade of retinal degeneration and the location of retinal degeneration. In females at all doses, the ratio of central/hemisphere to diffuse retinal degeneration increased. The ratio of bilateral lesions between men and women in the 1.0g/kg group was significantly higher than that in the control group. In the evaluation of peripheral retinal degeneration, compared with the control group, the average severity levels of males in the 0.3g/kg group and 1.0g/kg group and females in the 1.0g/kg group and 1.0g/kg group were in a dose-dependent manner There was no significant difference in the frequency of peripheral retinal degeneration between males and females or between treated and control animals. Acrylamide administration group: male, the frequency of retinal degeneration in the 0.7mM group was significantly increased compared to the control group. There were no significant differences in the average severity of retinal degeneration, the ratio of bilateral changes, and the location of retinal degeneration. In the assessment of peripheral retinal degeneration, there was no change in frequency and average severity in any group. In females, there was no change in the frequency of retinal degeneration in any group compared with the control group, although this trend was significant. Compared with the control group, the proportion of bilateral changes in the 0.70mM group was significantly increased. There was no significant difference between the average severity grade of retinal degeneration and the location of retinal degeneration. In the assessment of peripheral retinal degeneration, there was no change in frequency and average severity in any group. White malachite green group: Female, the frequency of retinal degeneration in the 543ppm group was significantly higher than that in the control group, but there was no significant difference in the average severity of retinal degeneration and the location of retinal degeneration. In all dose ranges, central/hemispherical relative diffuse retinal degeneration increased. In the evaluation of peripheral retinal degeneration, the average severity level of the 543ppm group was significantly increased compared with the control group, but the frequency of peripheral retinal degeneration in each group did not change significantly.

　　Conclusion: Three chemicals induce a related increase in retinal degeneration. According to the location of the lesion, it is speculated that these three chemicals may aggravate light-induced retinal degeneration. Optical microscopic evaluation of glass slides prepared by the correct orientation of the eye to distinguish between retinal damage and retinal phototoxicity associated with the test article or to determine the interaction between the test article and ambient light that causes retinal degeneration. In long-term albino rodent toxicity studies, when retinal degeneration is found in a dose-dependent manner, the morphology and topography of the retinopathy should be evaluated, which can help distinguish the aggravation of photo-induced retinal degeneration or the direct phototoxicity of the test product. If the retinopathy has characteristics of light-induced changes, additional careful evaluation of other species (including pigmented animals) is performed.