Ratlarda Retrobulber Prostaglandin Analoğu Enjeksiyonunun Orbital Yağ Dokusu Üzerine Etkisinin Bilgisayarlı Tomografi ile ve Histolojik Olarak İncelenmesi
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Effect of Retrobulbar Injection of Prostaglandin Analogues on Orbital Fat in Rats-Histological Analysis and Computed Tomography Findings Purpose Periorbital fat atrophy is a known side effect of prostaglandin analogues (PA). This undesirable effect on orbital fat could have a role in some diseases, manifesting with increased orbital fat volume such as thyroid orbitopathy. There is only one pilot study in the literature investigating the effects of retrobulbar bimatoprost injection on orbital fat in three rats. The goal of this study is to evaluate the effect of retrobulbar PA injection on orbital fat by histological analysis and computed tomography (CT) in rat animal model. Methods 18 adult, male, Wistar-albino rats were randomly divided into 3 groups as bimatoprost, latanoprost and travoprost groups each consisting of 6 animals. The rats were given retrobulbar injections of 0.1 ml of bimatoprost (n=6), latanoprost (n=6) or travoprost (n=6) in the right orbit, and 0.1 ml of saline in the left orbit as a control. CT imaging was performed before and 3 weeks after the injection. Rats were euthanized, perfused, and postfixed at 3 weeks after injection. Exenterated orbital tissue was sectioned for histologic staining. Photos of the slides were transferred to the digital platform. Number of fat cells per unit area for each rat was calculated via Image J software application (Rasband, W.S., US National Institutes of Health, Bethesda, MD) by two masked investigators. Nuclear image analysis of stained orbital fat cells were used to discriminate apoptotic cells and cells suspected to be undergoing apoptosis from other cells based on parameters such as nuclear area, roundness and circularity. Weka Trainable Segmentation as a plugin to Image J was used to measure the orbital and orbital fat volume on axial computed tomography sections. Results Histological evaluation showed no significant difference in number of cells per unit area between the PA and saline injected control orbits in any of the groups. Nuclear image analysis of stained orbital fat cells showed no difference in nuclear area, roundness and circularity parameters between the PA and saline injected orbits in any of the groups. CT imaging analysis showed no significant difference in orbital fat volume between the PA and saline injected orbits in any of the groups. Likewise, on the PA injected sides, there were no significant difference in the orbital fat volume before and after the injection in any of the groups. Conclusion No significant orbital fat atrophy was demonstrated on radiologic and histological analysis 3 weeks after retrobulber PA injection compared to control orbits in rat animal model. There was also no significant difference in apoptosis parameters in nuclear analysis. Further studies with more subjects investigating higher concentration of the drug in other animal models are needed in order to consider retrobulber PA injection as a potential therapy for diseases presenting with increased orbital fat volume like thyroid orbitopathy.