Gene Manipulation of Human Embryonic Stem Cells by In Vitro-Synthesized mRNA for Gene Therapy

The difficulty in producing genetically modified human embryonic stem cells (hESCs) limits research on their applications. Virus-based gene transfer is not safe for clinical use, whereas DNAbased non-viral methods are not efficient or safe, and mRNA-based methods are useful for genetic manipulation. In this study, we easily obtained multiple types and large amounts of in vitro-synthesized mRNA by PCR. The efficiency of different transfection methods was studied by flow cytometry. The effect of different mRNA modifications on protein translation efficiency and dynamics of luciferase mRNA expression in hESCs were studied using a bioluminescence imaging system. The pluripotency of hESCs after transfection was studied by immunofluorescence. In vitro-synthesized pancreatic-duodenal homeobox 1 (PDX1) mRNA was used to induce the differentiation of hESCs into insulin-producing cells. We found that electroporation is the most efficient transfection method, and it produces more than 95% transgene expression in multiple hESC lines. Synthesized mRNA with a combination of a polyA tail, cap and base analogues is more efficiently translated into protein in hESCs compared with single-modified mRNA. Transfection of mRNA into hESCs by trypsinizing the cells into single-cell suspensions did not affect their pluripotency, and multiple types of mRNAs can be transfected into hESCs efficiently. We found that PDX-1 mRNA transfection significantly improved the expression level of genes related to beta cells and differentiated cells that express insulin and C-peptide. ELISA analysis validate the insulin secretion of islet-like cell clusters in response to glucose stimulation. Our results indicate that electroporation of in vitro-synthesized mRNA is useful for genetic manipulation of hESCs and differentiation of hESCs into particular cell types, and this finding will pave the way for clinical applications of this method.