By contrast, bone marrow mesenchymal stem cell-derived exosomes carrying miR-122-5p promote osteoblast proliferation in osteonecrosis of the femoral head, regulating Sprouty RTK Signaling Antagonist 2 (SPRY2) via the RTK/Ras/mitogen-activated protein kinase (MAPK) signaling pathway [62]. Here, SPRY2 is linked to osteonecrosis.