基于多模态功能磁共振研究视网膜色素变性melanopsin基因治疗的视路变化及其机制

Retinitis pigmentosa (RP) is a group of hereditary progressive retinopathy. Currently, there is no effective methods in the prevention and treatment for RP in clinic. Recent studies have suggested that otogenetics is the most promising method for treating RP patients. However, the improvement of visual function after the treatment can only be integrally and roughly accessed by electroretinogram and visual evoked potential examinations. Therefore, it is very urgent to find a new technique, which can comprehensively, concretely and deeply evaluate the structural, functional and metabolic changes of each part in the visual pathway of RP patients before and after otogentics treatment. Our previous studies have shown that multi-modal functional MRI can quantitatively detect the axonal degeneration of nerve fibers in the visual pathway, the decrease of neuronal excitability and abnormal levels of neurotransmitters in the binocularly blind rats. Thus, this project aims to investigate the changes of structural, functional connections, whole brain network and metabolic biomarker in the visual pathway and related brain regions in RCS rats (the classic animal model of RP) at different stages of pre- and post-treatment with otogenetics (melanopsin gene) therapy by using multi-modal functional MR imaging combined with electrophysiological, behavioral experiments and histopathology to make clear the value of multi-modal functional MRI in the evaluation of the therapeutic effect. The goal of our project is also to explore the dynamic changes and mechanisms of visual functional recovery of RCS rats after treatment and to provide a theoretical basis for multi-modal functional MR imaging in the application of clinical diagnosis and treatment in the patients with RP and retinal degeneration diseases.

视网膜色素变性（RP）是一组遗传性进行性视网膜变性疾病，目前临床尚无有效的防治措施。新近研究发现，光遗传学技术是极具前景的治疗方法，但治疗后视功能的改善仅能通过视网膜电图、视觉诱发电位等方法整体粗略地评估。因此，迫切需要一种可以全面、具体、深入地评估治疗前、后RP患者球后视路各解剖部位结构、功能和生化代谢变化的新技术。我们前期研究发现，多模态功能磁共振（fMRI）可定量检测双眼盲大鼠视路轴索退变、神经元兴奋性下降和神经递质异常，因此，本项目拟采用多模态fMRI结合电生理、行为学及组织学方法，分别研究光遗传学（melanopsin基因）治疗前、后不同时间点RCS大鼠（RP经典模型）视路及相关脑区的结构与功能连接、全脑网络和代谢标志物等改变，以明确多模态fMRI在疗效评价中的作用，阐明其视功能恢复的动态变化规律及发生机制，并为多模态fMRI应用于RP等视网膜退行性疾病的临床诊治提供理论依据。

视网膜色素变性（RP）是一组遗传性进行性视网膜变性疾病，目前临床尚无有效的防治措施。新近研究发现，光遗传学技术是极具前景的治疗方法，但治疗后视功能的改善仅能通过视网膜电图、视觉诱发电位等方法整体粗略地评估。本项目采用多模态fMRI结合电生理、行为学及组织学方法，分别研究光遗传学（melanopsin基因）治疗前、后不同时间点RCS大鼠（RP经典模型）视路及相关脑区的结构与功能连接、全脑网络和代谢标志物等改变，以明确多模态fMRI在疗效评价中的作用，阐明其视功能恢复的动态变化规律及发生机制，并为多模态fMRI应用于RP等视网膜退行性疾病的临床诊治提供理论依据。本研究发现RP不仅能够引起视网膜水平的退变或重构，还能够引起视觉中枢及其相关脑区结构、功能及生化代谢的改变，提示RP可能是累及全脑的神经退行性疾病；RP中枢退行性改变的组织学基础主要包括：神经元数目减少、功能活动减低、胶质细胞大量增生、髓鞘丢失、轴突及神经纤维数目减少等；光遗传学melanopsin基因治疗能够有效地挽救RCS大鼠的视觉功能，且治疗后大鼠视觉中枢及其相关脑区可发生修复或适应性重塑；光遗传学melanopsin基因治疗后修复或适应性重塑的组织学基础主要包括：神经元活动增高、髓鞘及轴突形成增多、神经纤维修复等。293T（对照细胞）、661W细胞（视网膜色素上皮细胞）及原代神经节细胞在转染AAV-ONP4-GFP载体72h后荧光表达量增加，转染率分别约为90%、70%及50%。与RCS大鼠未干预组相比，melanopsin基因治疗后RCS大鼠视觉皮层NAA/Cr、Glu/Cr及Tau/Cr水平显著增加（P<0.05）。melanopsin基因治疗后RD值减低的脑区MBP阳性细胞数较未干预组增加，而AD值增高的脑区MBP阳性细胞数较未干预组亦增加（P<0.05）。静息态功能磁共振成像显示melanopsin基因治疗后,与未干预组相比, RCS大鼠双侧视觉皮层(T=4.5)、躯体感觉皮层(T=3.2)、运动皮层(T=3.4)、尾壳核(T=4.1)及右侧听觉皮层(T=3.6)、海马(T=4.3) ReHo显著增高(P<0.05, GRF校正后)。多模态功能磁共振能够应用于光遗传学melanopsin基因治疗RP的疗效评估，为探寻更加有效的临床治疗靶点和策略起到积极的推动作用。