Oxygen-induced pathological angiogenesis promotes intense lipid synthesis and remodeling in the retina

The retina is a notable tissue with high metabolic needs which relies on specialized vascular networks to protect the neural retina while maintaining constant supplies of oxygen, nutrients and dietary essential fatty acids. Here we determined the lipid content of the developing mouse retina under healthy and pathological angiogenesis using the oxygen-induced retinopathy model (OIR). In the OIR model, pathological angiogenesis is induced in mice through their exposure to variable oxygen levels. Thus, mouse pups with their nursing mothers were kept at 75% O2 from postnatal day 7 (P7) until day 12 (P12). Mice were then returned to ambient air (20.8% O2) and retinas (N=6) were collected at different time points (P12, P12.5, P15 and P17) and used in a lipid extraction procedure. Retinas from mouse pups under physiological development (controls) were also collected. Total lipid extracts were then used for a comprehensive non-targeted lipidomic analysis, whose quantitative results for 300 lipid species are presented here (‘Inague and Alecrim et al - Lipidomics Data’ spreadsheet). Lipidomics data was integrated with previously obtained transcriptomics data (SRA: SRP155931; BioProject: PRJNA483866). By matching the lipid profile to changes in the mRNA transcriptome, we identified a lipid signature associated with oxygen-induced retinopathy. Our data show that pathological angiogenesis leads to intense lipid remodeling favoring pathways for neutral lipid synthesis, cholesterol import/export and lipid droplet formation. The lipid signature also indicates that, from its early stages, pathological angiogenesis induces profound changes in pathways for the production of long-chain fatty acids, vital for retinal homeostasis. The net result is the production of large quantities of mead acid, a marker of essential fatty acid deficiency, which might also be an important marker for retinopathy severity. In sum, our lipid signature might contribute to a better understanding of many diseases of the retina that lead to vision impairment or blindness. This lipid signature might also be important for the development of additional translational therapies for retinopathy and other angiogenesis-dependent diseases.

视网膜是一类代谢需求极高的特殊组织，其依赖特化的血管网络，在维持氧气、营养物质及膳食必需脂肪酸持续供应的同时，保护神经视网膜。本研究借助氧诱导视网膜病变模型（oxygen-induced retinopathy model, OIR），解析了健康状态与病理血管生成状态下发育中小鼠视网膜的脂质组成。在该模型中，通过使小鼠暴露于可变氧浓度环境，可诱导其发生病理血管生成。具体实验流程如下：将出生后第7天（postnatal day 7, P7）至第12天（postnatal day 12, P12）的幼鼠与其哺乳母鼠一同置于75%氧气环境中，随后将其放回氧浓度为20.8%的正常空气环境，并在P12、P12.5、P15及P17等不同时间点收集视网膜样本（N=6），用于脂质提取流程。同时收集生理发育状态下幼鼠的视网膜作为对照样本。提取得到的总脂质随后被用于全面的非靶向脂质组学分析（non-targeted lipidomic analysis），本数据集包含300种脂质的定量结果，详见"Inague and Alecrim et al - Lipidomics Data" 电子表格。本研究将脂质组学数据与此前获取的转录组学数据（SRA: SRP155931; BioProject: PRJNA483866）进行了整合分析。通过将脂质谱与mRNA转录组的变化进行关联，本研究鉴定出了与氧诱导视网膜病变相关的脂质特征。研究数据表明，病理血管生成会引发剧烈的脂质重塑，该重塑优先激活中性脂质合成、胆固醇进出口及脂滴（lipid droplet）形成相关通路。该脂质特征还显示，病理血管生成从早期阶段便会对长链脂肪酸生成通路造成显著扰动，而长链脂肪酸对维持视网膜稳态至关重要。最终的效应是大量生成二十碳三烯酸（mead acid）——一种必需脂肪酸缺乏的特异性标志物，其也可能成为评估视网膜病变严重程度的重要标志物。综上，本研究得到的脂质特征或有助于加深对多种可导致视力受损或失明的视网膜疾病的认知，同时也可为视网膜病变及其他血管生成依赖性疾病的新型转化治疗开发提供理论参考与实践指导。