Improved generation of patient-specific induced pluripotent stem cells using a chemically-defined and matrigel-based approach.

Reprogramming of somatic cells into patient-specific pluripotent analogues of human embryonic stem cells (ESCs) emerges as a prospective therapeutic angle in molecular medicine and a tool for basic stem cell biology. However, the combination of relative inefficiency and high variability of non-defined culture conditions precluded the use of this technique in a clinical setting and impeded comparability between laboratories. To overcome these obstacles, we sequentially devised a reprogramming protocol using one lentiviral-based polycistronic reprogramming construct, optimized for high co-expression of OCT4, SOX2, KLF4 and MYC in conjunction with small molecule inhibitors of non-permissive signaling cascades, such as transforming growth factor β (SB431542), MEK/ERK (PD0325901) and Rho-kinase signaling (Thiazovivin), in a defined extracellular environment. Based on human fetal liver fibroblasts we could efficiently derive induced pluripotent stem cells (iPSCs) within 14 days. We attained efficiencies of up to 10.97±1.71% resulting in 79.5- fold increase compared to non-defined reprogramming using four singular vectors. We show that the overall increase of efficiency and temporal kinetics is a combinatorial effect of improved lentiviral vector design, signaling inhibition and definition of extracellular matrix (Matrigel®) and culture medium (mTESR®1). Using this protocol, we could derive iPSCs from patient fibroblasts, which were impermissive to classical reprogramming efforts, and from a patient suffering from familial platelet disorder. Thus, our defined protocol for highly efficient reprogramming to generate patient-specific iPSCs, reflects a big step towards therapeutic and broad scientific application of iPSCs, even in previously unfeasible settings.