Endoplasmic reticulum stress signals in defined human embryonic stem cell lines and culture conditions.

Human embryonic stem cells (hESCs) are especially resistant to several cellular stresses, but the existence and induction of Endoplasmic Reticulum (ER) stress by culture conditions are unknown. Using qPCR, here, we investigated the behavior of the principal sensors of ER stress and their relation with the feeder layer, the type of conditioned media used in feeder free systems and the upregulation of several differentiation markers. We observed the preservation of pluripotency, and detected differential expression of differentiation markers in HS181 and SHEF1 hESCs growing on Adipose-derived mesenchymal stem cells (ASCs) and feeder-free system with different conditioned media (HEF-CM and ASC-CM). Taken together, these results demonstrate evidence of ER stress events that cells must resolve to survive and maintenance of markers of pluripotency. The early differentiation status defined could progress into a more differentiated state, and may be influenced by culture conditions.