Therapeutic effect of human umbilical cord MSC exosomes in osteonecrosis, attributing the anti-apoptotic and pro-survival effects of MSC exosomes to miR-21-mediated downregulation of PTEN (phosphatase and tensin homolog) and AKT (protein kinase B) phosphorylation (Kuang et al., 2019). The gene discussed is AKT1; the disease is osteonecrosis.