ERN1 and chronic kidney disease: CKD-induced endoplasmic reticulum (ER) stress in human MSCs was evaluated by measuring the expression levels of ER stress markers, protein kinase R-like endoplasmic reticulum kinase (PERK), eukaryotic translation initiation factor 2 alpha (eIF2a), activating transcription factor 4 (ATF4), inositol-requiring enzyme 1 alpha (IRE1a), c-Jun N-terminal kinase (JNK), and CCAAT-enhancer-binding proteins (C/EBP) homologous protein (CHOP).