Immunohistochemical characterization of the mandibular condyle for type I and II collagen, aggrecan, MMP-9, and MMP-13 in MMP-2-deficient mice.

Mice devoid of matrix metalloproteinase (MMP)-2 due to gene targeting have been reported to show articular cartilage destruction in the knee joint; however, the phenotype of the mandibular condylar cartilage remains unknown. Thus, in the present study, we investigated the mandibular condyle in Mmp2 mice. We obtained and bred Mmp2 mice from the same source as the previous study, and performed genotyping using genomic DNA extracted from finger snips. The mandibular condyle of Mmp2 mice and wild-type (WT) mice was immunohistochemically examined for the localization of extracellular matrix (ECM) proteins (type I and II collagen, and aggrecan), and MMP-9 and MMP-13. No cartilage destruction was observed in the mandibular condyle of Mmp2 mice, and no difference was found in the localization of the ECM proteins between the Mmp2 mice and WT mice. However, the bone marrow cavity in the subchondral bone of the mandibular condyle was more distinct in Mmp2 mice than in WT mice at the age of 50 weeks. Of note, MMP-9 characteristically localized in multinucleated cells in the mandibular condyle in 50-week-old Mmp2 mice. MMP-2 may be involved in the regulation of osteoclast differentiation and the formation of the bone marrow cavity in aged mice.