Department of Ophthalmology, University of California, San Francisco, San Francisco, California 94143, USA.
Invest Ophthalmol Vis Sci. 2012 Jan 5;53(1):76-84. doi: 10.1167/iovs.11-8546.
To examine the functional significance of EphB/ephrin-B upregulation in mouse experimental glaucoma.
In a loss-of-function approach, mouse mutants lacking EphB2 (EphB2(-/-)) or EphB3 (EphB3(-/-)) protein, and mutants expressing EphB2 truncated in the C-terminus (EphB2(lacZ/lacZ)) were subjected to laser-induced ocular hypertension (LIOH), an experimental mouse model of glaucoma. The number of optic nerve axons was counted in paraphenylenediamine (PPD)-stained sections and compared between EphB mutants and wild type littermates. In a gain-of-function approach, retina/optic nerve explants obtained from LIOH-treated animals were exposed to EphB2-Fc recombinant proteins or Fc control proteins. Tissue sections through the optic nerve head (ONH) were labeled with neuron-specific anti-tubulin β-III antibody to determine axonal integrity.
Both EphB2 and EphB3 null mutant mice exhibited more severe axonal degeneration than wild type littermates after treatment with LIOH. Mutant mice in which the C-terminal portion of EphB2 is truncated had an intermediate phenotype. Application of EphB2-Fc recombinant protein to LIOH-treated optic nerve explants resulted in greater sparing of tubulin β-III-containing retinal ganglion cell (RGC) axons.
These results provide genetic evidence in mice that both EphB/ephrin-B forward and reverse signaling feed into an endogenous pathway to moderate the effects of glaucomatous insult on RGC axons. LIOH-induced axon loss is maintained in retina/optic nerve explants after removal from an ocular hypertensive environment. Exogenous application of EphB2 protein enhances RGC axon survival in explants, suggesting that modulation of Eph/ephrin signaling may be of therapeutic interest.
研究 EphB/ephrin-B 上调在小鼠实验性青光眼中的功能意义。
在功能丧失的方法中，缺乏 EphB2（EphB2(-/-)）或 EphB3（EphB3(-/-)）蛋白的小鼠突变体，以及表达 EphB2 羧基末端截断的突变体（EphB2(lacZ/lacZ)），都被进行激光诱导的眼内压升高（LIOH），这是一种青光眼的实验性小鼠模型。用对苯二胺（PPD）染色的切片计数视神经轴突的数量，并与 EphB 突变体和野生型同窝仔鼠进行比较。在功能获得的方法中，将从 LIOH 处理的动物中获得的视网膜/视神经外植体暴露于 EphB2-Fc 重组蛋白或 Fc 对照蛋白。通过视神经头（ONH）的组织切片用神经元特异性抗微管蛋白β-III 抗体标记，以确定轴突的完整性。
在接受 LIOH 治疗后，EphB2 和 EphB3 缺失突变小鼠的轴突退化比野生型同窝仔鼠更为严重。截断 EphB2 的羧基末端部分的突变小鼠表现出中间表型。将 EphB2-Fc 重组蛋白应用于 LIOH 处理的视神经外植体，导致含有微管蛋白β-III 的视网膜神经节细胞（RGC）轴突的更大程度的保留。
这些结果为小鼠提供了遗传证据，即 EphB/ephrin-B 的正向和反向信号都进入内源性途径，以减轻青光眼损伤对 RGC 轴突的影响。从高眼压环境中取出后，LIOH 诱导的轴突丢失在视网膜/视神经外植体中得以维持。外源性应用 EphB2 蛋白增强外植体中 RGC 轴突的存活，表明 Eph/ephrin 信号的调节可能具有治疗意义。
