A poptosis of hypertrophic chondrocytes in rat cartilaginous growth plate |
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Authors: | Ikuo Fujita Soichiro Hirata Hitoshi Ishikawa Kosaku Mizuno Hiroshi Itoh |
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Institution: | (1) Department of Orthopedic Surgery, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, 650 Kobe, Japan;(2) First Department of Pathology, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, 650 Kobe, Japan |
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Abstract: | Calcifying cartilages undergo endochondral ossification, a process in which cartilage is replaced by bone. These tissues contain
chondrocytes that proliferate, leading, to differentiation and hypertrophy. Recent histological and biochemical studies suggest
that hypertrophic chondrocytes undergo apoptosis. We investigated the process of this cell death to determine when fragmentation
of DNA, a hallmark of apoptosis, occurs during cellular commitment to hypertrophy, and to test the hypothesis that the chondrocytes
are intrinsically programmed to undergo apoptosis. End-labeling of fragmented DNA of rat proximal tibiae revealed that a majority
of hypertrophic cells bore fragmented DNA, indicating that apoptosis was in progress in this zone. In pelleted chondrocyte
cultures isolated from, rat rib growth plates and employed in an in vitro model of a growth plate, hypertrophic cells were
also positive for end-labeling. Gel electrophoresis of DNA isolated from the chondrocyte cultures at 1–3 weeks yielded the
ladder formation characteristic of apoptosis. We conclude that the chondrocytes in the growth plate are programmed to self-annihilate
by apoptosis and that the apoptotic process is closely associated with the commitment to hypertrophy. |
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Keywords: | apoptosis hypertrophic chondrocyte growth plate endochondral ossification |
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