APP and Alzheimer disease: Previous studies using cellular and/or animal models of AD have shown that exosomes secreted from neurons and astrocytes can serve as carriers for APP, APP-CTFs and/or Aβ peptides, which can either exacerbate or attenuate AD pathology (Fernandes et al., 2018; Laulagnier et al., 2018; Lauritzen et al., 2019; Rajendran et al., 2006; Sharples et al., 2008; Sullivan et al., 2011; Vingtdeux et al., 2007; Xie et al., 2019).