Dear Editor,
Stem cell therapy holds enormous and revolutionary promise to treat various age-related diseases,such as diabetes,heart failure,and Parkinson's disease.However,low retention and survival rate of delivered stem cells,partially due to immuno-logical rejection,constitute major hurdles for the clinical implementation of stem cell therapy(Lei et al.,2021a).Since mounting evidence showed that several types of stem cells mainly exert their therapeutic effects through the secretion of paracrine effects,exosomes,which are released by stem cells and execute most paracrine functions,have begun to draw attention in the field(Tran and Damaser,2015).