Researchers developed a method to generate induced pluripotent stem cells (iPSCs) using recombinant proteins instead of genetic material. This approach avoids the risks associated with integrating foreign DNA into the genome, which is a concern with traditional iPSC methods. The study used recombinant reprogramming proteins fused with a poly-arginine domain to penetrate cell membranes and reprogram murine embryonic fibroblasts. These proteins were expressed in E. coli, solubilized, refolded, and purified. The proteins entered cells efficiently and translocated to the nucleus, demonstrating their ability to reprogram cells. After four cycles of treatment, the cells were able to form colonies that expressed pluripotency markers. The generated piPSCs were characterized and found to be morphologically and functionally similar to conventional mouse embryonic stem cells (mESCs). They could differentiate into cells from all three germ layers and contributed to the germline in vivo. The study highlights the potential of this protein-based method for safer and more efficient iPSC generation, offering advantages over existing genetic methods. The method uses a chemically defined regimen, allowing for broader and more economical application. The research provides evidence that recombinant reprogramming proteins can fully reprogram somatic cells into pluripotent stem cells, representing a significant advancement in iPSC technology.Researchers developed a method to generate induced pluripotent stem cells (iPSCs) using recombinant proteins instead of genetic material. This approach avoids the risks associated with integrating foreign DNA into the genome, which is a concern with traditional iPSC methods. The study used recombinant reprogramming proteins fused with a poly-arginine domain to penetrate cell membranes and reprogram murine embryonic fibroblasts. These proteins were expressed in E. coli, solubilized, refolded, and purified. The proteins entered cells efficiently and translocated to the nucleus, demonstrating their ability to reprogram cells. After four cycles of treatment, the cells were able to form colonies that expressed pluripotency markers. The generated piPSCs were characterized and found to be morphologically and functionally similar to conventional mouse embryonic stem cells (mESCs). They could differentiate into cells from all three germ layers and contributed to the germline in vivo. The study highlights the potential of this protein-based method for safer and more efficient iPSC generation, offering advantages over existing genetic methods. The method uses a chemically defined regimen, allowing for broader and more economical application. The research provides evidence that recombinant reprogramming proteins can fully reprogram somatic cells into pluripotent stem cells, representing a significant advancement in iPSC technology.