Experimental studies in various animals showed that using a coculture system with direct cell-to-cell contact with mesenchymal stem cells (MSCs) significantly upregulated the biological activity of nucleus pulposus (NP) cells. Activated NP cells can be reinserted into the disc to inhibit intervertebral disc degeneration. In human cells, the positive effects of the coculture system with direct cell-to-cell contact seen in animal studies were also evaluated and cell proliferation, DNA synthesis, and PG synthesis were significantly upregulated. Chromosome abnormalities and tumorigenesis were not observed in the activated NP cells. Then the authors have started the specially designed clinical trial under the control of Ministry of Health, Labour and Welfare and now post operative follow-up has been continued with expected good outcome.