Induced pluripotent stem cell-derived fibroblasts efficiently engage senescence pathways but show increased sensitivity to stress inducers

The risk of malignant transformation of induced pluripotent stem cells (iPSC)-derived cells in re-sponse to DNA damage is a concern knowing that the tumor suppressor genes TP53 and CDKN2A are transiently inactivated during reprogramming. Here, we evaluated the integrity of cellular senescence pathways and DNA double strand break (DSB) repair in iPSC-derived human fibro-blasts (i-HF) compared to their parental skin fibroblasts (HF). Using a variety of functional assays, we show that the capacity of i-HF to enter senescence and repair DSB is not compromised after damage induced by ionizing radiation (IR) or overexpression of H-RASV12. Still, i-HF lines are transcriptionally different from their parental lines, showing enhanced metabolic activity and higher expression of p53-related effector genes. As a result, i-HF lines generally exhibit increased sensitivity to various stresses, have an elevated senescence associated secretory phenotype (SASP) and cannot be immortalized unless p53 expression is knocked down. In conclusion, while our results suggest that i-HF are not at a greater risk of transformation, their overall hyperactivation of se-nescence pathways may impede their function as a cell therapy product. To evaluate the tumorigenic potential of iPSC-derived cells,we used human fibroblasts (HF) isolated from skin biopsies of three different donors and measured their ability to enter senescence and to repair double strand DNA damage in comparison with their autologous iPSC-derived counterparts (i-HF). HF were collected from three different donors (HF1: Adult male (41 years old), HF2: Adult female (39 years old), HF3: Foetal) We also performed gene expression profiling analysis using three donors of parental and iPSC-derived fibroblasts at basal state (Ctl) and 8 hours post a 15 Gy dose of irradiation.