An immunohistochemical and ultrastructural study of the pericellular matrix of uneroded hypertrophic chondrocytes in the mandibular condyle of aged c-src-deficient mice.
OBJECTIVE
Previous studies indicate that hypertrophic chondrocytes can transdifferentiate or dedifferentiate and redifferentiate into bone cells during the endochondral bone formation. Mandibular condyle in aged c-src-deficient mice has incremental line-like striations consisting of cartilaginous and non-cartilaginous layers, and the former contains intact hypertrophic chondrocytes in uneroded lacunae. The purpose of this study is to determine the phenotype changes of uneroded hypertrophic chondrocytes.


METHODS
Immunohistochemical and ultrastructural examinations of the pericellular matrix of hypertrophic chondrocytes in the upper, middle, and lower regions of the mandibular condyle were conducted in aged c-src-deficient mice, using several antibodies of cartilage/bone marker proteins.


RESULTS
Co-localisation of aggrecan, type I collagen, and dentin matrix protein-1 (DMP-1) or matrix extracellular phosphoprotein (MEPE) was detected in the pericellular matrix of the middle region. Ultrastructurally, granular substances in the pericellular matrix of the middle region were the remains of upper region chondrocytes, which were mixed with thick collagen fibrils. In the lower region, the width of the pericellular matrix and the amount of collagen fibrils were increased. Versican, type I collagen, DMP-1, and MEPE were detected in the osteocyte lacunae. Additionally, DMP-1 and MEPE were detected in the pericellular matrix of uneroded hypertrophic chondrocytes located in the lower, peripheral region of the mandibular condyle in younger c-src-deficient mice, but not in the aged wild-type mice.


CONCLUSIONS
These results indicate that long-term survived, uneroded hypertrophic chondrocytes, at least in a part, acquire osteocytic characteristics.
Shibata
Shunichi
S
Division of Histology, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, 1757 Kanazawa, Tobetsu-cho, Ishikari-gun, Hokkaido, Japan. sshibata@hoku-iryo-u.ac.jp
Baba
Otto
O
Oda
Tsuyoshi
T
Yokohama-Tamaki
Tamaki
T
Qin
Chunlin
C
Butler
William T
WT
Sakakura
Yasunori
Y
Takano
Yoshiro
Y
D053674:Aggrecans / Q000032:analysis; D000375:Aging / Q000502:physiology*; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D019902:Chondrocytes / Q000473:pathology / Q000648:ultrastructure*; D024042:Collagen Type I / Q000032:analysis; D024043:Collagen Type II / Q000032:analysis; D024121:Collagen Type X / Q000032:analysis; D005109:Extracellular Matrix / Q000737:chemistry / Q000648:ultrastructure; D016326:Extracellular Matrix Proteins / Q000032:analysis; D006023:Glycoproteins / Q000032:analysis; D006984:Hypertrophy; D007150:Immunohistochemistry; D008335:Mandibular Condyle; D051379:Mice; D008817:Mice, Mutant Strains; D046529:Microscopy, Electron, Transmission; D010750:Phosphoproteins / Q000032:analysis; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000172:deficiency*; D053675:Versicans / Q000032:analysis
D053674:Aggrecans; D015415:Biomarkers; D024042:Collagen Type I; D024043:Collagen Type II; D024121:Collagen Type X; C513308:Dmp1 protein, mouse; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; C518716:Mepe protein, mouse; D010750:Phosphoproteins; D053675:Versicans; D016392:Proto-Oncogene Proteins pp60(c-src)