Intravitreal injection of 99Tc-MDP inhibits the development of laser-induced choroidal neovascularization in rhesus monkeys |
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Authors: | Kunbei Lai Chenjin Jin Shu Tu Yunfan Xiong Rui Huang Jian Ge |
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Institution: | 1. State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, 54 South Xianlie Road, Guangzhou, 510060, China
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Abstract: | Background The aim of this study was to investigate the safety and efficacy of intravitreal injection of 99Tc-MDP, a decay product of 99mTc-MDP, on the development of laser-induced choroidal neovascularization (CNV) in rhesus monkeys. Methods Experimental CNV was induced by argon laser with a small high-energy laser spot. Monkeys were given 50 μL of 99Tc-MDP at a concentration of 0.005 μg/mL (n?=?6) or 0.01 μg/mL (n?=?6) by intravitreal injection once a week immediately after laser injury for a period of 56 days. Control animals were treated with the same volume of PBS (n?=?6) in the same way. Eyes were monitored by ophthalmic examination, color fundus photography, fluorescence fundus angiography (FFA), optical coherence tomography (OCT) and histology. Incidences of grade 4 CNV lesions as well as the leakage areas of grade 4 CNVs on the late-phase of fluorescein angiograms were measured in a standardized, randomized and masked fashion fortnightly. The maximum widths and heights of grade 4 CNVs were also calculated by histology at the end of the experiment. Toxicity of 99Tc-MDP on the retina was evaluated by electroretinogram (ERG) and histologic analysis. Results 99Tc-MDP reduced the incidences of grade 4 CNVs by 33.33 % and 39.40 % in the 0.005 μg/mL and 0.01 μg/mL groups, respectively, compared with the PBS group on day 28 (P?<?0.05; n?=?6). The leakage areas of grade 4 CNVs were smaller in the 0.005 μg/mL (0.7136?±?0.0283 mm2, p <0.01; n?=?6) and 0.01 μg/mL (0.4351?±?0.0349 mm2, p?<?0.01; n?=?6) groups than those in the PBS control group (0.9373?±?0.0455 mm2; n?=?6) in a dose-dependent manner on day 28. OCT and histology also showed that the sizes of CNVs were smaller in the 99Tc-MDP treated groups than those in the PBS group. Although intravitreal injection of 99Tc-MDP led to mild inflammatory reaction in the anterior chamber, histology and ERG findings demonstrated that 99Tc-MDP did not cause any change in histological structure or function of the retina (p>0.05). Conclusions Intravitreal injection of 99Tc-MDP can inhibit the development of laser-induced CNV without toxic effect on retina, suggesting that 99Tc-MDP has therapeutic potential for CNV related diseases. |
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