mRNA lipid nanoparticles reprogram blood cells into heart-ready stem cells in far fewer passages

Induced pluripotent stem cells (iPSCs) are central to disease modeling, drug and cardiac-safety screening, and future cell therapies. For over a decade, non-integrating Sendai virus has been the gold standard for reprogramming. But it is a replicating vector that must be diluted out over roughly 10 or more passages, and it requires viral-clearance testing and added regulatory oversight. Those burdens grow as biobanks scale to hundreds of donor lines. A virus-free alternative that is gentle on cells could lower cost and time.

This study compared Sendai virus reprogramming with an mRNA-lipid nanoparticle (mRNA-LNP) kit that delivers mRNAs for five factors (Oct4, SOX2, KLF4, c-Myc, LIN28) via receptor-mediated endocytosis. Both methods were applied to PBMCs from the same donor, who carried the long QT syndrome type 2 KCNH2 c.2398+5G>T variant. This gave an identical genetic starting point. The iPSCs were assessed for colony morphology, pluripotency markers (immunostaining and flow cytometry), trilineage differentiation, karyotype, STR identity, and variant retention by Sanger sequencing. They were then differentiated into ventricular-like cardiomyocytes and tested on multielectrode arrays.

Both methods produced iPSCs with typical colony morphology, expression of SSEA4, SOX2, TRA-1-81, TRA-1-60, and Oct-4, trilineage capacity, normal karyotypes, and preserved KCNH2 variant. The mRNA-LNP workflow was faster: colony picking was done by passage 2 versus 10, morphology and pluripotency characterization by passage 3 versus 11, and genomic characterization by passage 4 versus 11. This translated into a 63.6% reduction in passaging media and consumables per clone, with about five days per passage.

Cardiomyocytes from both lines showed troponin T–positive sarcomeres, formed electrically coupled syncytia, and produced field potentials and ventricular-like action potentials. Average APD90 was 595.5 ms for Sendai-derived and 634.3 ms for mRNA-LNP-derived cells (n = 28 each, from 5 differentiations). Both fall within the published long QT2 range (about 516–881 ms) and above typical healthy values (about 243–373 ms). The mRNA-LNP approach does require repeated dosing (an initial treatment plus three more), unlike the single Sendai infection.

The findings suggest mRNA-LNP reprogramming is a practical, virus-independent route for biobanking and precision medicine, preserving early-passage cells. However, this is a proof-of-concept in one donor and one disease, so broader validation is needed.