CD274 and ischemic stroke: The study shows the therapeutic potential of programmed death‐ligand 1 (PD‐L1) and hepatocyte growth factor (HGF)‐engineered human telomerase reverse transcriptase‐immortalized adipose tissue‐derived mesenchymal stem cell‐derived exosomes (EXO‐PD‐L1‐HGF) in promoting neuroprotection, anti‐inflammation, and neurogenesis following ischemic stroke.