SPP1 and osteoarthritis: HMOX1-activated HO-1 is associated with the prevention of various diseases, including cancer, diabetes, cardiovascular disease, and osteoarthritis [40–43], and current studies have shown that HMOX1 may play a role in maintaining bone homeostasis, increased expression of HMOX1 can increase the levels of osteopontin (OPN), osteoprotegerin (OPG) and bone morphogenetic protein-2 (BMP-2) [44].