High-efficiency cellular reprogramming with microfluidics

We report that the efficiency of reprogramming human somatic cells to induced pluripotent stem cells (hiPSCs) can be dramatically improved in a microfluidic environment. Microliter-volume confinement resulted in a 50-fold increase in efficiency over traditional reprogramming by delivery of synthetic mRNAs encoding transcription factors. In these small volumes, extracellular components of the TGF-β and other signaling pathways exhibited temporal regulation that appears critical to acquisition of pluripotency. The high quality and purity of the resulting hiPSCs (μ-hiPSCs) allowed direct differentiation into functional hepatocyte- and cardiomyocyte-like cells in the same platform without additional expansion. We performed cell reprogramming of human foreskin BJ fibroblasts, seeded on a feeder layer of inactivated human newborn foreskin fibroblasts NuFF-RQs, by modified mRNA (mmRNA) daily transfections of OCT4, SOX2, KLF4,c-MYC, NANOG, LIN28, and nuclear GFP for 18 days. The process was performed in parallel in 6-well plates and within a microfluidic system. 48 hours after last reprogramming mmRNA transfection, 4 freshly derived colonies of comparable size were selected both from the microfluidic system and from a parallel reprogramming experiment in well. After a 24 h conditioning in StemMACS Brew XF medium, each colony was split in two halves: one was stopped at passage p0 and used for total RNA extraction, the other one was further expanded in feeder-free conditions for 3 passages (p3) in well before total RNA extraction from another sectioned colony of comparable size. Thus, the overall study includes: (i) N=4 p0 hiPS colonies reprogrammed in well, (ii) N=4 p0 hiPS colonies reprogrammed in microfluidics, (iii) N=4 p3 hiPS colonies (the same as in (i)) expanded in well, (iv) p3 hiPS colonies (the same as in (ii)) expanded in well.