Direct reprogramming of fibroblasts into endothelial cells capable of angiogenesis and reendothelialization in tissue-engineered vessels

TLDR

Induced pluripotent stem cells are a key tool for regenerative medicine, but their use is limited by tumorigenic risk. The study aimed to develop a tumor‑safe partial‑iPS method that converts human fibroblasts into endothelial cells. The method uses four reprogramming factors to create PiPS cells, which, upon VEGF stimulation, induce SETSIP translocation to the nucleus, bind the VE‑cadherin promoter, and drive endothelial differentiation. PiPS cells, generated by transient expression of OCT4, SOX2, KLF4, and c‑MYC, did not form tumors, differentiated into functional endothelial cells via SETSIP‑mediated VE‑cadherin upregulation, and enhanced neovascularization, blood flow recovery, and vessel scaffold integration in a hindlimb ischemia model, indicating clinical promise.

Abstract

The generation of induced pluripotent stem (iPS) cells is an important tool for regenerative medicine. However, the main restriction is the risk of tumor development. In this study we found that during the early stages of somatic cell reprogramming toward a pluripotent state, specific gene expression patterns are altered. Therefore, we developed a method to generate partial-iPS (PiPS) cells by transferring four reprogramming factors (OCT4, SOX2, KLF4, and c-MYC) to human fibroblasts for 4 d. PiPS cells did not form tumors in vivo and clearly displayed the potential to differentiate into endothelial cells (ECs) in response to defined media and culture conditions. To clarify the mechanism of PiPS cell differentiation into ECs, SET translocation (myeloid leukemia-associated) (SET) similar protein (SETSIP) was indentified to be induced during somatic cell reprogramming. Importantly, when PiPS cells were treated with VEGF, SETSIP was translocated to the cell nucleus, directly bound to the VE-cadherin promoter, increasing vascular endothelial-cadherin (VE-cadherin) expression levels and EC differentiation. Functionally, PiPS-ECs improved neovascularization and blood flow recovery in a hindlimb ischemic model. Furthermore, PiPS-ECs displayed good attachment, stabilization, patency, and typical vascular structure when seeded on decellularized vessel scaffolds. These findings indicate that reprogramming of fibroblasts into ECs via SETSIP and VEGF has a potential clinical application.