The contribution of the epicardium, the outermost layer of the heart, to cardiac regeneration has remained controversial due to a lack of suitable analytical tools. By combining genetic marker-independent lineage-tracing strategies with transcriptional profiling and loss-of-function methods, we report here that the epicardium of the highly regenerative salamander species Pleurodeles waltl has an intrinsic capacity to differentiate into cardiomyocytes. Following cryoinjury, CLDN6⁺ epicardium-derived cells appear at the lesion site, organize into honeycomb-like structures connected via focal tight junctions and undergo transcriptional reprogramming that results in concomitant differentiation into de novo cardiomyocytes. Ablation of CLDN6⁺ differentiation intermediates as well as disruption of their tight junctions impairs cardiac regeneration. Salamanders constitute the evolutionarily closest species to mammals with an extensive ability to regenerate heart muscle and our results highlight the epicardium and tight junctions as key targets in efforts to promote cardiac regeneration.

由于缺乏合适的分析工具，心外膜（心脏的最外层）对心脏再生的贡献仍然存在争议。通过将不依赖遗传标记的谱系追踪策略与转录分析和功能丧失方法相结合，我们在此报告，高度再生蝾螈物种Pleurodeles waltl的心外膜具有分化为心肌细胞的内在能力。冷冻损伤后，CLDN6 ⁺心外膜来源的细胞出现在病变部位，组织成通过局灶性紧密连接连接的蜂窝状结构，并经历转录重编程，导致同时分化为新生心肌细胞。CLDN6 ⁺分化中间体的消融以及其紧密连接的破坏会损害心脏再生。蝾螈是进化上最接近哺乳动物的物种，具有广泛的心肌再生能力，我们的研究结果强调心外膜和紧密连接是促进心脏再生的关键目标。