SPP1 and intervertebral disk degenerative disorder: However, considering the difficulties in local drug delivery in the CEP of the mouse lumbar spine and the diversity of ways in which OPN functions, we did not evaluate the therapeutic effect of OPN-targeted therapy in IDD mice, such as local injection of OPN-expressing adeno-associated virus or recombinant OPN protein, which becomes a shortcoming of this study as well as our future research focus.