Relevance of Positional Memory of Fibroblasts in Reprogramming to Induced Pluripotent Stem Cells

Induced Pluripotent Stem cells (iPSC) are adult skin fibroblasts (sFB) genetically reprogrammed to an embryonic stem cell-like state. Notwithstanding their autologous origin and their potential to differentiate towards cells of all three germ layers, iPSC reprogramming is still affected by low efficiency.We hypothesize that the variability in the sFB reprogramming is due to the sFB used, as sFB derived from different anatomic sites exhibit topographic differentiation and preserve positional memory. Human sFB harvested from five different anatomical sites (neck, breast, arm, abdomen, thigh) were cultured for one week and their morphology, proliferation, and expression of mesenchymal or epithelial markers were evaluated by immunocytochemistry. Additionally, gene expression profile analysis was performed by real-time PCR including genes typically expressed in mesenchymal cells, and involved in cell growth, proliferation, development, andmorphogenesis. Intriguingly, while the morphology of sFB derived from different anatomical sites differed only slightly, proliferation rate and expression of distinctive markers varied greatly. Further, different sFB had different genetic program. Interestingly, sFB derived from neck and breast shared genetic signature of Mesenchymal Stem Cells, raising doubts about the existence of two distinct cell population. Since sFB topographic origin defines their genetic programitmight remarkably affect the efficiency of reprogramming. Hence, according to our evidence, it is mandatory to carefully select sFB population when planning sFB reprogramming for regenerative medicine purposes.