TRIM21 and osteosarcoma: Zhang et al. found that TRIM21 facilitated the translocation of ANXA2 toward the plasma membrane and subsequently led to cell differentiation by inducing autophagy in osteosarcoma cells.76 AnxA5 was also found to participate in autophagic regulation.24 We showed that MVs induced autophagy via AnxA5 and thus promoted osteogenic differentiation in BMSCs (Fig. 5).