To provide a composition for treating periodontal disease, a method of developing periodontal ligament, and a polypeptide, a polynucleotide, a recombinant expression vector and a transformant to be used therefor, it was identified that human ADAMTSL4a protein, human ADAMTSL4ß protein, mouse ADAMTSL4a protein and mouse ADAMTSL4ß protein are factors regulating a periodontal ligament regeneration process. Periodontal ligament can be developed using a composition containing any of these proteins, a composition containing a transformant into which a gene encoding any of these proteins has been introduced, a recombinant expression vector containing a gene encoding any of these proteins. As a result, a tissue destroyed by periodontal disease can be repaired.
