PTEN and osteonecrosis: Kuang et al. (2019) observed therapeutic efficacy of human umbilical cord (UC) MSC-EVs in osteonecrosis and attributed the anti-apoptotic and pro-survival effects of MSC-EVs to miR-21-mediated PTEN (phosphatase and tensin homolog) downregulation and AKT (protein kinase B) phosphorylation.