BMP2 and ossification of the posterior longitudinal ligament of the spine: In the present study, immunohistochemical localization of BMP2 was examined using ligament tissues from the OPLL and non-OPLL patients, the results were consistent with the previous studies that BMP2 were present at the ossifying matrix and chondrocytes of ossifying ligaments, and also localized at mesenchymal cells adjacent to these areas [42].