Generation of specialized blood vessels via lymphatic transdifferentiation. Generation of specialized blood vessels via lymphatic transdifferentiation

The lineage and developmental trajectory of a cell are key determinant s of cellular identity. In the vascular system, endothelial cells (ECs) of blood and lymphatic vessels (LVs) differentiate and diversify to cater the different physiological demands of each organ . While LVs are known to originate from multiple origins , lymphatic ECs (LECs) themselves are not known to generate other cell - types . Here, we u s e recurrent imaging and lineage - tracing of ECs in zebrafish anal fins (AF) from early development through adulthood , to uncover an unexpected mechanism of specialized blood vessel formation through transdifferentiation of LECs . Moreover, we demonstrate distinct functional implications for deriving AF vessels from either LECs or blood ECs, uncovering a link between cell ontogeny and functionality. We further use scRNA - seq to characterize the different cellular populations and transition states involved in the transdifferentiation process . Finally, we show that akin to its normal development, the vasculature is re - derived from lymphatics during AF regeneration, demonstr ating that LECs in adult fish retain both potency and plasticity for generating blood ECs . Overall, our work highlights a new innate mechanism of blood vess el formation through LEC trans differentiation, and provides in vivo evidence for a link between cell ontogeny and functionality in ECs Overall design: 80 anal fins from immature zebrafish were digested. Sorting and RNA extraction was performed on fli1a:dsRed positive cells

细胞的谱系与发育轨迹是决定细胞身份的核心要素。在血管系统中，血液与淋巴管（lymphatic vessels, LVs）的内皮细胞（endothelial cells, ECs）会发生分化与多样化，以适配各器官的不同生理需求。目前已知淋巴管起源于多种发育源头，但学界尚未明确淋巴管内皮细胞（lymphatic ECs, LECs）自身能够生成其他细胞类型。本研究通过对斑马鱼臀鳍（anal fins, AF）从发育早期至成年阶段的内皮细胞开展反复成像与谱系追踪，揭示了一条通过淋巴管内皮细胞转分化形成特化血管的意外机制。此外，本研究证实了由淋巴管内皮细胞或血液内皮细胞分化而来的臀鳍血管具有截然不同的功能特性，进而揭示了细胞个体发生与功能之间的关联。我们进一步通过单细胞RNA测序（single-cell RNA sequencing, scRNA-seq）对转分化过程中涉及的各类细胞群与过渡状态进行了表征。最后，我们发现与正常发育过程一致，斑马鱼臀鳍再生过程中的血管系统同样源自淋巴管，证明成体斑马鱼的淋巴管内皮细胞仍具备生成血液内皮细胞的潜能与可塑性。综上，本研究揭示了一种通过淋巴管内皮细胞转分化形成血管的全新先天机制，并为内皮细胞的细胞个体发生与功能之间的关联提供了体内实验证据。整体实验设计：将80条未成熟斑马鱼的臀鳍进行消化处理，对fli1a:dsRed阳性细胞进行分选并提取RNA。