短波长光干预豚鼠光学离焦性近视进展的作用机制研究

Myopia is the most common eye problem that causes visual dysfunction. The prevalence of myopia is increasing year by year, while the prevention and mechanism of myopia haven't made a breakthrough. Recently, more and more attentions are paid to the effect of chromatic signals on myopia development. Our previous study showed that short-wavelength light could not only inhibit elongation of vitreous body in normal guinea pigs but also prevent the development of defocus-induced myopia in guinea pigs. In addition, there had been some changes in the distribution and number of cones in retina as well as the expression of the opsin and the retinoic acid. We assumed that retinoic acid associated signals play important roles in defocus-induced myopia inhibited by short-wavelength light. We will observe the refractive state and the expression of important myopic related factors such as retinoic acid, Egr-1, dopamine, TGF-β2 and MMP-2/TIMP-2 in defocus-induced myopia inhibited by short-wavelength light. Furthermore, we will feed the animal with exogenous retinoic acid and competitive inhibitor of the dehydrogenases responsible for the generation of retinoic acid. Thus, we intend to figure out the mechanism that short-wavelength light inhibit the development of defocus-induced myopia. This research is a further study on the basis of the one-year project of NSFC in 2013 by which we will understand how the short-wavelength light intervenes myopia and find a novel way to prevent myopia.

近视是最常见引起视力障碍的眼病，近年来近视患病率逐年上升，但近视防治仍没有大的突破，根本原因在于近视的发病机制尚不明确。色觉信号在近视形成中的作用越来越受到关注，我们课题组前期研究发现短波长光不仅可抑制正常豚鼠眼球玻璃体腔的延长，还可有效抑制豚鼠光学离焦性近视的进展,并发现其伴随有视网膜视锥细胞数量及分布改变、视蛋白表达改变、视黄酸发生变化。我们推测短波长光阻滞近视进展的可能作用机制是通过视黄酸信号通路完成。本课题将观察430nm短波长光干预豚鼠离焦性近视后屈光状态及近视相关信号因子（视黄酸、Egr-1、多巴胺、TGF-β2、MMP-2/TIMP-2等）的改变，并通过外源性补充视黄酸及给予视黄酸合成酶抑制剂两种途径，深入揭示短波长光抑制光学离焦性近视的机制。本项目是2013年国家自然科学基金面上项目（1年期）的进一步深入研究，本研究将明确短波长光阻滞近视的机制，为近视的防治提供全新的途径。

前期研究发现短波长光可有效抑制豚鼠离焦性近视的进展，并发现其伴有视网膜视锥细胞数量及分布改变、视蛋白表达改变、视网膜中视黄酸(RA)含量发生变化。在此基础上本课题研究了短波长光干预离焦性近视的作用机制及外源性视黄酸及其抑制剂与短波长光交互作用对豚鼠离焦性近视的影响。课题分三部分进行。第一部分将2周龄豚鼠随机分成短波长光组(SL组)和白光组(BL组) ，两组右眼均配戴-5D镜片，左眼为自身对照，实验前及实验后1、2、4周进行眼球的生物学测量，并通过观察不同视锥细胞的密度及分布，检测视网膜中视黄酸含量、视黄酸相关受体(RAR-β)、巩膜MMP-2、TGFβ及胶原的表达，探究短波长光对近视干预的作用机制。结果显示，4周时，SL组双眼间屈光度差异小于BL组(p=0.04)，右眼眼轴也较BL组短(p=0.02)；SL组双眼视黄酸含量明显少于BL组(OD: p=0.001, OS: p<0.001)，且RARβ表达减少(p=0.04)，其余相关受体表达也发生改变，SL 组视网膜铺片显示M视锥细胞在各区域表达减少，S视锥细胞表达增加；HE染色显示巩膜明显变厚。第二部分将2周龄豚鼠分为白光RA组和短波长光RA组，两组豚鼠均喂食RA，其余干预方式及检测指标均同第一部分。结果显示，BL组喂食RA后近视明显加深(p<0.001)，而SL组与正常饮食组无明显差异(p=0.52)，且双眼间屈光差异明显少于BL组(p<0.001)；而两组视网膜中RA含量均升高，相关受体的表达也发生明显变化。第三部分将2周龄豚鼠分为白光柠檬醛组和短波长光柠檬醛组，两组均喂食柠檬醛，其余干预方式及检测指标均同第一部分。结果显示，两组近视进展及玻璃体腔增长均小于正常饮食和喂食RA的豚鼠，虽然白光组眼轴的增长量几乎是短波长光组的2倍，但离焦诱导的近视(OD-OS)两组无明显差异(p=0.47)，此外，戴镜眼视网膜中视黄酸浓度降低，但未戴镜眼与正常饮食组的视黄酸含量无明显差异。以上结果提示，430nm短波长光可以有效减缓豚鼠离焦性近视的进展，同时发现，短波长光阻滞近视的机制可能是通过减少视网膜中视黄酸的浓度，而通过外源性补充视黄酸合成抑制剂可以有效阻滞离焦性近视的形成。