Chen Yao, Shi Chun-Yan, Li Ying, Hu Yun-Tao, Han Hong-Bin, Sun Xiao-Dong, Salvi Satyajeet S, Ma Zhi-Zhong
Department of Ophthalmology, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Peking University Third Hospital, Beijing 100191, China.
Department of Radiology, Key Laboratory of Magnetic Resonance Imaging Equipment and Technology, Peking University Third Hospital, Beijing 100083, China.
Chin Med J (Engl). 2016 Aug 5;129(15):1822-9. doi: 10.4103/0366-6999.186630.
Manganese-enhanced magnetic resonance imaging (MEMRI) for visual pathway imaging via topical administration requires further research. This study investigated the permeability of the corneal epithelium and corneal toxicity after topical administration of Mn2+ to understand the applicability of MEMRI.
Forty New Zealand rabbits were divided into 0.05 mol/L, 0.10 mol/L, and 0.20 mol/L groups as well as a control group (n = 10 in each group). Each group was further subdivided into epithelium-removed and epithelium-intact subgroups (n = 5 in each subgroup). Rabbits were given 8 drops of MnCl2in 5 min intervals. The Mn2+ concentrations in the aqueous and vitreous humors were analyzed using inductively coupled plasma-mass spectrometry at different time points. MEMRI scanning was carried out to image the visual pathway after 24 h. The corneal toxicity of Mn2+ was evaluated with corneal imaging and pathology slices.
Between the aqueous and vitreous humors, there was a 10 h lag for the peak Mn2+ concentration times. The intraocular Mn2+ concentration increased with the concentration gradients of Mn2+ and was higher in the epithelium-removed subgroup than that in the epithelium-intact subgroup. The enhancement of the visual pathway was achieved in the 0.10 mol/L and 0.20 mol/L epithelium-removed subgroups. The corresponding peak concentrations of Mn2+ were 5087 ± 666 ng/ml, 22920 ± 1188 ng/ml in the aqueous humor and 884 ± 78 ng/ml, 2556 ± 492 ng/ml in the vitreous body, respectively. Corneal injury was evident in the epithelium-removed and 0.20 mol/L epithelium-intact subgroups.
The corneal epithelium is a barrier to Mn2+, and the iris and lens septum might be another intraocular barrier to the permeation of Mn2+. An elevated Mn2+ concentration contributes to the increased permeation of Mn2+, higher MEMRI signal, and corneal toxicity. The enhancement of the visual pathway requires an effective Mn2+ concentration in the vitreous body.
通过局部给药进行视觉通路成像的锰增强磁共振成像（MEMRI）需要进一步研究。本研究调查了局部给予Mn2+后角膜上皮的通透性和角膜毒性，以了解MEMRI的适用性。
将40只新西兰兔分为0.05 mol/L、0.10 mol/L和0.20 mol/L组以及对照组（每组n = 10）。每组再进一步分为去上皮和上皮完整亚组（每个亚组n = 5）。每隔5分钟给兔子滴8滴MnCl2。在不同时间点使用电感耦合等离子体质谱法分析房水和玻璃体液中的Mn2+浓度。24小时后进行MEMRI扫描以对视觉通路成像。用角膜成像和病理切片评估Mn2+的角膜毒性。
在房水和玻璃体液之间，Mn2+浓度峰值时间存在10小时的延迟。眼内Mn2+浓度随Mn2+浓度梯度增加，且去上皮亚组高于上皮完整亚组。在0.10 mol/L和0.20 mol/L去上皮亚组中实现了视觉通路的增强。相应的Mn2+峰值浓度在房水中分别为5087±666 ng/ml、22920±1188 ng/ml，在玻璃体中分别为884±78 ng/ml、2556±492 ng/ml。在去上皮和0.20 mol/L上皮完整亚组中角膜损伤明显。
角膜上皮是Mn2+的屏障，虹膜和晶状体隔膜可能是眼内另一个Mn2+渗透屏障。升高的Mn2+浓度有助于增加Mn2+的渗透、更高的MEMRI信号和角膜毒性。视觉通路的增强需要玻璃体中有有效的Mn2+浓度。
