A study in humans identified the mir-520d-3p as a diagnostic microRNA upregulated in serum following mild traumatic brain injury, where it targets 1566 genes and is part of a robust signaling signature involving MAPK, TGF-β, and other pathways that is concomitantly reflected across serum, plasma, and saliva [Matyasova et al. DOI:10.4149/gpb_2021038].