According to Si et al. 18, osteopontin is involved in activities related to the proliferation, migration, and adhesion of different bone cells, including bone marrow mesenchymal stem cells, hematopoietic stem cells, osteoclasts, and osteoblasts, as well as its relationship with diseases such as osteoporosis, rheumatoid arthritis, and osteosarcoma. The gene discussed is SPP1; the disease is rheumatoid arthritis.