flt1 inactivation promotes zebrafish cardiac regeneration by enhancing endothelial activity and limiting the fibrotic response. flt1 inactivation promotes zebrafish cardiac regeneration by enhancing endothelial activity and limiting the fibrotic response

VEGFA administration has been explored as a pro-angiogenic therapy for cardiovascular diseases including heart failure for several years; however, many challenges remain. Here we investigate a different approach to augmenting VEGFA bioavailability, one that achieves more physiological VEGFA concentrations by deleting VEGFR1/FLT1, a VEGFA decoy receptor. We find that, following cryoinjury, zebrafish flt1 mutant hearts display enhanced coronary revascularization and endocardial expansion, increased cardiomyocyte dedifferentiation and proliferation, and decreased scarring. Suppressing Vegfa signaling in flt1 mutants abrogates the beneficial effects of flt1 deletion. Transcriptomic analyses of cryoinjured flt1 mutant hearts revealed enhanced endothelial MAPK/ERK signaling and downregulation of the transcription factor gene egr3. Using genetic tools, we observe egr3 upregulation in the regenerating endocardium and find that Egr3 promotes myofibroblast differentiation. These data suggest that with enhanced VEGFA bioavailability, the cardiac endothelium limits myofibroblast differentiation via egr3 downregulation, thereby providing a more permissive microenvironment for cardiomyocyte replenishment after injury. Overall design: Comparative gene expression analysis between cryoinjured wild-type zebrafish ventricles and flt1 mutant ventricles at 96 hours post-cryoinjury.

多年来，血管内皮生长因子A（VEGFA）给药策略被广泛探索用于包括心力衰竭在内的心血管疾病的促血管生成治疗，但目前仍存在诸多挑战。本研究旨在探索一种提升VEGFA生物利用度的全新途径：通过敲除VEGFA诱饵受体血管内皮生长因子受体1/Fms样酪氨酸激酶1（VEGFR1/FLT1），可实现更符合生理状态的VEGFA浓度水平。我们发现，在冷冻损伤后，斑马鱼flt1突变体心脏可呈现出更显著的冠状动脉血管重建与心内膜扩张、更明显的心肌细胞去分化与增殖，同时瘢痕形成显著减少。在flt1突变体中抑制Vegfa信号通路，可抵消flt1敲除带来的有益效应。对冷冻损伤的flt1突变体心脏开展转录组分析后发现，其内皮细胞的丝裂原活化蛋白激酶/细胞外调节蛋白激酶（MAPK/ERK）信号通路活性增强，且转录因子基因egr3的表达水平下调。借助遗传操作工具，我们观察到再生心内膜中egr3的表达出现上调，并证实Egr3可促进肌成纤维细胞分化。上述数据表明，在VEGFA生物利用度提升的情况下，心脏内皮细胞可通过下调egr3的表达抑制肌成纤维细胞分化，从而为损伤后心肌细胞的补充与修复提供更为适宜的微环境。总体实验设计：于冷冻损伤后96小时，对冷冻损伤的野生型斑马鱼心室与flt1突变体心室进行比较基因表达分析。