Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Smith Building M002, 400 North Broadway Baltimore, MD 21287, USA.
Exp Eye Res. 2012 Jun;99(1):27-35. doi: 10.1016/j.exer.2012.04.006. Epub 2012 Apr 25.
The purpose of this study was to improve a mouse model of chronic intraocular pressure (IOP) elevation utilizing microbead injection in two strains of mice and to assess the effect of age and anesthesia on measured IOP. We compared our previous model with two modified protocols for injecting polystyrene microbeads and viscoelastic material in CD1or C57BL/6 mice. The measured outcomes were degree of IOP elevation and production of axonal loss. The first new protocol was injection of 3 μL of equal volumes of 6 μm and 1 μm diameter beads, followed by 2 μL of viscoelastic (3+2). The second new protocol injected 4 μL of the two bead mixture, then 1 μL of viscoelastic (4+1). Both were compared to injection of 2 μL of 6 μm beads with 3 μL of viscoelastic (2+3). We also compared the effects of age and of two anesthetic regimens (intraperitoneal ketamine/xylazine/acepromazine versus isoflurane gas) on measured IOP in untreated eyes of both strains. IOP was 2mm Hg lower with intraperitoneal than with gas anesthesia in both strains (p=0.003, p<0.0001, t-test). IOP measurements were lower in untreated young (2 months) compared to older (10 months) C57BL/6 mice (p=0.001, t-test). In the experimental glaucoma mouse model, mean IOP and number of elevated IOP measurements were higher in newer protocols. Mean axon loss with the 4+1 protocol (all strains) was twice that of the 2+3 and 3+2 protocols (36% vs. 15% loss, p=0.0026, ANOVA), and mean axon loss in CD1 mice (21%) was greater than in C57BL/6 mice (13%) (p=0.047, ANOVA). Median axon loss in 4+1 protocol treated C57BL/6 mice expressing yellow fluorescent protein in 2% of retinal ganglion cells (RGCs) had greater median axon loss than C57BL/6 4+1 protocol treated mice (26% vs. 10%, p=0.03). The 4+1 protocol provided higher, more consistent IOP elevation and greater axonal loss. The effects of age, strain, and anesthesia on induced IOP elevation and axon damage must be considered in mouse experimental glaucoma research.
本研究旨在改进慢性眼内压（IOP）升高的小鼠模型，方法是在两种小鼠品系中使用微珠注射，并评估年龄和麻醉对测量的 IOP 的影响。我们比较了以前的模型和两种改良方案，即向 CD1 或 C57BL/6 小鼠中注射聚苯乙烯微珠和粘性弹性物质。测量的结果是IOP 升高的程度和轴突丢失的程度。第一个新方案是注射 3 μL 等体积的 6 μm 和 1 μm 直径的珠子，然后再注射 2 μL 粘性弹性物质（3+2）。第二个新方案是注射 4 μL 两种珠子混合物，然后再注射 1 μL 粘性弹性物质（4+1）。这两种方案都与注射 2 μL 6 μm 珠子和 3 μL 粘性弹性物质（2+3）进行了比较。我们还比较了年龄和两种麻醉方案（腹腔内氯胺酮/甲苯噻嗪/乙酰丙嗪与异氟烷气体）对两种品系未治疗眼测量的 IOP 的影响。两种品系的腹腔内麻醉比气体麻醉的 IOP 低 2mmHg（p=0.003，p<0.0001，t 检验）。在未治疗的年轻（2 个月）C57BL/6 小鼠中，IOP 测量值比年龄较大（10 个月）的 C57BL/6 小鼠低（p=0.001，t 检验）。在实验性青光眼小鼠模型中，新方案的平均 IOP 和IOP 升高测量值更高。4+1 方案的平均轴突丢失（所有品系）是 2+3 和 3+2 方案的两倍（36%对 15%的丢失，p=0.0026，方差分析），CD1 小鼠（21%）的平均轴突丢失高于 C57BL/6 小鼠（13%）（p=0.047，方差分析）。在表达视网膜神经节细胞（RGC）中 2%黄色荧光蛋白的 C57BL/6 小鼠中，4+1 方案治疗的中位轴突丢失高于 C57BL/6 4+1 方案治疗的小鼠（26%对 10%，p=0.03）。4+1 方案提供了更高、更一致的 IOP 升高和更大的轴突丢失。在小鼠实验性青光眼研究中，必须考虑年龄、品系和麻醉对诱导的 IOP 升高和轴突损伤的影响。
