Evalution os Early sclerochorioretinal abnormalities in hypercholesterolemic rabbits treated with Rosiglitazone

The purpose of this study is to evaluate scleral, choroid and retinal abnormalities in rabbits induced by a hypercholesterolemic diet and the prevention of these abnormalities after oral administration of rosiglitazone in rabbits. Fifty-four new zealand rabbits were divided into four groups: the control group (CG) was fed a normal diet; group 1 G1), a hypercholesterolemic diet; group 2 (G2) a hypercholesterolemic diet associated with daily administration of 3 mg of rosiglitazone from day 14 after the beginning of the diet; and group 3 G3), a hypercholesterolemic diet associated with daily administration of 3 mg of rosiglitazone since the beginning of the experiment. The rabbits were weighed and underwent the following examinations: seric dosages of total cholesterol, triglycerides, cholesterol HDL, and fasting glycemia at the beginning of the experiment, on the 14th day and on the 42nd, the euthanasia day. The sclera and choroid underwent histologic and histomorphometric analyses and the retina underwent immunohistochemical analysis with anti-calretinin (CR) and anti-glial fibrillary acidic protein (GFAP) antibody. When positive for the anti-calretinin marker, two quantitative analyses were performed. In the first analysis, all immunoreactive ganglion cells were counted. In the second analysis, all immunoreactive cells and cell elements were studied with the color morphometry method. The data were evaluated using the nonparametric Kruskal-Wallis and the Shapiro – Wilk tests. Values of p<0.05 were considered statistically significant. The results obtained showed a significant weight increase in Groups 1 and 3 in relation to CG on Day 14 (p<0.009). Additionally, a significant weight increase was observed in G1, G2 and G3 in relation to CG on Day 42 (p<0.023). The lab results showed a significant increase in glucose and total cholesterol in G1 in relation to CG (p<0.001) on Day 14, as well as a significant HDL increase in G3, when compared with the other groups (p<0.001) on Day 14. HDL in G3 was significantly high when compared to the other groups, on the euthanasia day (p<0.001). The results obtained regarding weight showed a significant increase in Groups 1, 2 and 3 in relation to CG on Day 14 (p<0.01) and Day 42 (p<0.02). The lab results showed a significant increase in glucose and total cholesterol in Groups 1, 2 and 3 in relation to CG (p<0.01) on Day 14, as well as a significant increase in HDL in G3 when compared with the other groups, on euthanasia day (p<0.01). The histomorphometric analysis of CG sclera and choroid presented normal results. Conversely, G1 showed a significant increase in sclera and choroid thickness in relation to CG (p= 0,008), whereas G3 showed thickness lower than in G1 (p=0,048). A larger number of histiocytes were observed on the scleral wall of the group that was fed the hypercholesterolemic diet (G1), followed, in a descending order, by groups 2 and 3, and the control group. The immunohistochemical analysis of the retina with the anti-calretinin monoclonal antibody showed that G1 presented a larger number of immunoreactive ganglion cells than G3 (p = 0.002). The color morphometry showed significant immunoreactivity of G1 cells and cell elements when compared with the other groups (p<0.001). A significant immunoreactivity of G2 and G3 cells and cell elements in relation to CG was also observed (p<0.002). GFAP results were negative in all groups. The findings of this proposed study model suggest that hypercholesterolemia induces early histomorphometric and immunohistochemical abnormalities in the sclerochorioretinal complex and that the activation of PPAR gamma in ocular cells attenuated these abnormalities with the administration of the oral rosiglitazone diet.O objetivo deste trabalho é avaliar as anormalidades da esclera, coroide e retina de coelhos induzidas pela dieta hipercolesterolêmica, além da possibilidade de prevenção dessas anormalidades com administração sistêmica de rosiglitazona. Para isto, 54 coelhos new zealand foram distribuídos em quatro grupos: grupo-controle (GC) recebeu dieta normal; grupo 1 recebeu dieta hipercolesterolêmica; grupo 2 recebeu dieta hipercolesterolêmica associada à administração diária de 3 mg de rosiglitazona a partir do 14º dia do início do experimento; e grupo 3 recebeu dieta hipercolesterolêmica associada à administração diária de 3 mg de rosiglitazona desde o início do experimento. Os coelhos foram pesados e submetidos à dosagem sérica de colesterol total, triglicerídeos, high density lipoprotein (HDL) colesterol e glicemia de jejum no início do experimento, no 14º dia e no momento da eutanásia (42º dia). A esclera e coroide foram submetidas à análise histológica e histomorfométrica. A retina foi submetida à análise imuno-histoquímica com o anticorpo monoclonal anticalretinina (CR) e anticorpo anti-glial fibrillary acidic protein (GFAP). Quando positivo para o marcador anticalretinina, duas análises quantitativas foram realizadas. Na primeira, foram contadas todas as células ganglionares imunorreativas. Na segunda, todas as células e elementos celulares imunorreativos foram avaliados pelo exame de morfometria de cores. Os dados foram analisados pelo teste nãoparamétrico de Kruskal-Wallis e teste de Shapiro-Wilks-Testand. Valores abaixo de 0,05 foram considerados estatisticamente significantes. Os resultados referentes ao peso demonstraram significativo aumento nos grupos 1 e 3 em relação ao GC no 14º dia (p<0,009), enquanto no 42º dia os grupos 1, 2 e 3 apresentaram representativamente mais peso que o GC (p<0,023). Quanto às variáveis laboratoriais, destacaram-se o aumento significativo da glicose e colesterol total de G1 em relação ao controle (p<0,001), assim como o acentuado aumento da HDL no G3 em relação aos demais grupos (p<0,001), no 14º dia. A HDL manteve-se expressivamente elevada no G3 em relação aos demais grupos no momento da eutanásia (p<0,001). À análise histomorfométrica da esclera e coroide obteve-se normalidade do GC. Por outro lado, o G1 mostrou marcante aumento da espessura da esclera e coroide em relação ao GC (p=0,008), enquanto que no G3 houve espessamento de esclera e coroide menor que no G1 (p=0,048). Elevado número de histiócitos foi observado na parede escleral do grupo submetido à dieta hipercolesterolêmica (G1), seguido de forma decrescente por G2, G3 e GC. A análise imuno-histoquímica da retina com o anticorpo monoclonal anticalretinina ressaltou número mais alto de células ganglionares imunorreativas no G1 que no G3 (p=0,002). O exame de morfometria de cores revelou significativa imunorreatividade das células e elementos celulares do G1 em relação aos outros grupos (p