PTGER4 and Down syndrome: Decreases in CNP expression have been linked to AD and Down's syndrome.44 BDNF increases CNP in the brains and improves functional recovery and connectivity of animals with ischemic stroke.94 We observed that, in the EP4 antagonist‐elicited MSC EV/exosome‐treated damaged brains, the induced DCX‐positive neuronal precursor cells contained CNP protein (Figure S3).