A protocol for transdifferentiation of human cardiac fibroblasts into endothelial cells via activation of innate immunity

Endothelial cells (ECs) have emerged as key pathogenic players in cardiac disease due to their proximity with cardiomyocytes. Induced pluripotent stem cells (iPSCs) have been employed to generate ECs. However, it may be more clinically relevant to transdifferentiate fibroblasts into ECs directly without introducing pluripotent or virally driven transcription factors. Here, we present a protocol that describes the direct conversion of human cardiac fibroblasts into ECs by leveraging the innate immune system. Our protocol produces bona fide human ECs with 95%–98% purity by first passage.