Phenotypic switching of in vitro mandibular condylar cartilage during matrix mineralization |
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Authors: | Inoue Hiroyuki Hiraki Yuji Nawa Tokio Ishizeki Kiyoto |
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Institution: | Department of Molecular Interaction and Tissue Engineering, Institute for Frontier Medical Sciences, Kyoto University, Kyoto and; Department of Oral Anatomy, School of Dentistry, Iwate Medical University, Morioka, Japan |
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Abstract: | In order to analyze the phenotypic conversion of chondrocytes, mandibular condyles of mice and rabbits were cultured under
cell and organ culture systems, and then examined by a combination of morphological and biochemical procedures. In organ culture,
mandibular condylar cartilage (MCC) obtained from newborn mice began to mineralize from the central zone and then progressively
widened towards the peripheral zone. Electron microscopic observations showed that with the increasing duration of the organ
culture, chondrocytes at the central zone converted into spindle-shaped osteoblastic cells accompanying the formation of the
bone type of thick-banded collagen fibrils. To obtain a better understanding of the chondrocytic conversion, immunolocalizations
for type I and type X collagens and osteocalcin (OC) were examined in mouse MCC cells in cell culture. Type X collagen and
OC were expressed almost simultaneously at the late stage of culture, and type I collagen was detected along the calcified
nodues after the production of these proteins. Northern blot analysis in cell cultures of rabbit MCC indicated that type II
collagen and alkaline phosphatase (ALPase) messenger ribonucleic acids (mRNAs) were highly expressed at day 7, but subsequently
decreased. In contrast, mRNA for type I collagen was expressed at a low level on day 7 and peaked on day 12. The present results
suggest that, morphologically and biochemically, cellular modification in MCC cells under culture conditions occurs at a cellular
morphological level and also at marker-gene-expression level. |
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Keywords: | bone-marker genes cell culture chondrocyte mandibular condyle mineralization |
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