Generation of human induced pluripotent stem cells (hiPSCs) from fibroblasts and other somatic cells represents a highly promising strategy to produce auto- and allo-genic cell sources for therapeutic approaches as well as novel models of human development and disease1. Reprogramming protocols involve transduction of the Yamanaka factors Oct3/4, Sox2, Klf4, and c-Myc into the parental somatic cells, followed by culturing the transduced cells on mouse embryonic fibroblast (MEF) or human fibroblast feeder layers, and subsequent mechanical dissociation of pluripotent cell-like colonies for propagation on feeder layers. The presence of residual parental and feeder-layer cells introduces experimental variability, pathogenic contamination, and promotes immunogenicity. Similar to human embryonic stem cells (hESCs), reprogrammed hiPSCs suffer from the unavoidable problem of spontaneous differentiation due to sub-optimal feeder cultures4, growth factors5, and the feeder-free substrate. Spontaneously differentiated (SD)-hiPSCs display reduced pluripotency and often contaminate hiPSC cultures, resulting in overgrowth of cultures and compromising the quality of residual pluripotent stem cells5. Therefore, the ability to rapidly and efficiently isolate undifferentiated hiPSCs from the parental somatic cells, feeder-layer cells, and spontaneously differentiated cells is a crucial step that remains a bottleneck in all human pluripotent stem cell research.
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