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In situ hybridisation study of type I, II, X collagens and aggrecan mRNAs in the developing condylar cartilage of fetal mouse mandible

Published online by Cambridge University Press:  01 October 1999

KENJI FUKADA
Affiliation:
2nd Department of Orthodontics, School of Dentistry, Tokyo Medical and Dental University, Tokyo, Japan Department of Dental Pharmacology, School of Dentistry, Tokyo Medical and Dental University, Tokyo, Japan
SHUNICHI SHIBATA
Affiliation:
1st Department of Oral Anatomy, School of Dentistry, Tokyo Medical and Dental University, Tokyo, Japan
SHOICHI SUZUKI
Affiliation:
2nd Department of Orthodontics, School of Dentistry, Tokyo Medical and Dental University, Tokyo, Japan
KEIICHI OHYA
Affiliation:
Department of Dental Pharmacology, School of Dentistry, Tokyo Medical and Dental University, Tokyo, Japan
TAKAYUKI KURODA
Affiliation:
2nd Department of Orthodontics, School of Dentistry, Tokyo Medical and Dental University, Tokyo, Japan
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Abstract

The aim of this study was to investigate the developmental characteristics of the mandibular condyle in sequential phases at the gene level using in situ hybridisation. At d 14.5 of gestation, although no expression of type II collagen mRNA was observed, aggrecan mRNA was detected with type I collagen mRNA in the posterior region of the mesenchymal cell aggregation continuous with the ossifying mandibular bone anlage prior to chondrogenesis. At d 15.0 of gestation, the first cartilaginous tissue appeared at the posterior edge of the ossifying mandibular bone anlage. The primarily formed chondrocytes in the cartilage matrix had already shown the appearance of hypertrophy and expressed types I, II and X collagens and aggrecan mRNAs simultaneously. At d 16.0 of gestation, the condylar cartilage increased in size due to accumulation of hypertrophic chondrocytes characterised by the expression of type X collagen mRNA, whereas the expression of type I collagen mRNA had been reduced in the hypertrophic chondrocytes and was confined to the periosteal osteogenic cells surrounding the cartilaginous tissue. At d 18.0 of gestation before birth, cartilage-characteristic gene expression had been reduced in the chondrocytes of the lower half of the hypertrophic cell layer. The present findings demonstrate that the initial chondrogenesis for the mandibular condyle starts continuous with the posterior edge of the mandibular periosteum and that chondroprogenitor cells for the condylar cartilage rapidly differentiate into hypertrophic chondrocytes. Further, it is indicated that sequential rapid changes and reductions of each mRNA might be closely related to the construction of the temporal mandibular ramus in the fetal stage.

Type
Research Article
Copyright
© Anatomical Society of Great Britain and Ireland 1999

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