Patients with degenerative disc disease (DDD) experience serious clinical symptoms, including chronic low back pain. A series of therapies have been developed to treat DDD, including physical therapy and surgical treatment. However, the therapeutic effect of such treatments has remained insufficient. Recently, stem cell‑based therapy, in which stem cells are injected into the nucleus pulposus in degenerated intervertebral disc tissue, has appeared to be effective in the treatment of DDD. In the present study, the effect of adipose‑derived stem cells on degenerated nucleus pulposus cells was investigated using a co‑culture system to evaluate the biological activity of degenerated nucleus pulposus cells. Human degenerated nucleus pulposus tissue was obtained from surgical specimens and the adipose‑derived stem cells were derived from adipose tissue. The degenerated nucleus pulposus cells were cultured in a mono‑culture or in a co‑culture with adipose‑derived stem cells using 0.4‑µm Transwell inserts. The results indicated that adipose‑derived stem cells were able to stimulate matrix synthesis and the cell proliferation of degenerated nucleus pulposus cells, promoting the restoration of nucleus pulposus cells in the degenerated intervertebral disc.