PRNP and pulmonary fibrosis: Among the pathophysiological conditions, ischaemia/ROS‐induced ER stress is known to induce apoptotic cell death in host tissues as well as in the transplanted stem/progenitor cells.6, 7, 17, 29 To solve this issue, several studies have suggested that melatonin could be used to protect against ER stress in neurotoxic states, liver diseases, immunotoxic states, pulmonary fibrosis and diabetes.33 Our previous study revealed that melatonin could enhance MSC functionality for the treatment of ischaemic disease by upregulating the express of PrPC.