An object of the present invention is to provide an agent for promoting expression of N-acetylgalactosaminyltransferase that contains an extract from inflamed tissues inoculated with vaccinia virus. The present invention demonstrated that the extract from inflamed tissues inoculated with vaccinia virus promotes the expression of N-acetylgalactosaminyltransferase in intervertebral disc cells. Thus, the extract from inflamed tissues inoculated with vaccinia virus or a preparation containing the extract is useful as an agent for promoting the expression of N-acetylgalactosaminyltransferase in intervertebral disc cells.