Human Urinal Cell Reprogramming: Synthetic 3D Peptide Hydrogels Enhance Induced Pluripotent Stem Cell Population Homogeneity.

Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs), which have promising potential applications in regenerative medicine. However, the challenges of successful applications of human iPSCs for medical purposes are the low generation efficiency, heterogeneous colonies, and exposure to the animal-derived product Matrigel. We aimed to investigate whether human urinal cells could be efficiently reprogrammed into iPSCs in three-dimensional Puramatrix (3D-PM) compared to two-dimensional Matrigel (2D-MG) and to understand how this 3D hydrogel environment affects the reprogramming process. Human urinal cells were successfully reprogrammed into iPSCs in the defined synthetic animal-free 3D-PM. Interestingly, although the colony efficiency in 3D-PM was similar to that in 2D-MG (∼0.05%), the reprogrammed colonies in 3D-PM contained an iPSC population with significantly higher homogeneity, as evidenced by the pluripotent-like morphology and expression of markers. This was further confirmed by transcriptome profile analysis in bulk cells and at the single cell level. Moreover, the homogeneity of the iPSC population in 3D-PM colonies was correlated with the downregulation of integrin β1 (ITGB1) and phosphorylated focal adhesion kinase (FAK). Collectively, 3D-PM provides an alternative approach for obtaining iPSCs with enhanced homogeneity. This work also unveiled the regulation of human somatic cell reprogramming via the extracellular microenvironment.