[Messenger RNA for Cell Editing -Disease Treatment and Cell Transplantation Using Pro-survival mRNA]

Vigorous efforts are being made to manipulate cellular functions in a desirable manner for biomedical purposes. Recent advances in platform technologies have made cell editing achievable; this includes generation of induced pluripotent stem cells and chimeric antigen receptor T cells, as well as direct cell reprogramming. mRNA, as compared to DNA, is an excellent tool for potentiating cell editing technologies, owing to its distinct properties in gene introduction. Herein, hepatocytes were edited ex vivo and in vivo, by introducing pro-survival mRNA, to be resistant to cell death. DNA-based introduction of pro-survival gene poses safety concerns due to its genomic integration, as prolonged and uncontrolled expression of pro-survival proteins after the integration may promote cancer. In contrast, mRNA lacks such a risk. Moreover, mRNA-based introduction of Bcl-2, a pro-survival factor, was more effective in preventing the death of cultured hepatocytes than Bcl-2 plasmid DNA (pDNA) introduction. Mechanistically, mRNA induced protein expression in a larger percentage of the hepatocytes compared to pDNA, presumably because the process of pDNA nuclear entry in transfection is challenging. In hepatocyte transplantation to mouse liver, ex vivo introduction of Bcl-2 mRNA significantly improved the engraftment efficiency of the hepatocytes, leading to successful functional support of the liver in a mouse model of chronic hepatitis. Furthermore, in vivo administration of Bcl-2 mRNA exhibited an anti-apoptotic effect on the hepatocytes of a mouse model of fulminant hepatitis. These results demonstrate the potential advantages of mRNA introduction over DNA introduction in cell editing.