Evaluation of osteonectin expression in the mouse mandibular condyle
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The role of the condylar cartilage in mandibular growth has been an enduring concern in bone research. The goal of this investigation was to examine early cellular and molecular events during mandibular growth induced by mandibular protrusive posturing. Mandibular growth is preceded by chondrocyte proliferation and appositional cartilage matrix formation.Cellular proliferation was measured by tritiated thymidine incorporation in the TMJ region during DNA synthesis. Osteonectin, provided a marker for proliferating, and differentiating chondrocytes, and the chondroid matrix. Levels of osteonectin messenger RNA expression were determined by Northern blot analysis probed with osteonectin anti-sense mRNA or a CDNA probe. The osteonec protein was revealed by immunochistochemical localization with an anti-osteonectin monocIonal antibody. The treatment group data suggested increased cellular proliferation was induced by mandibular hyperpropulsion. The results were statistically analyzed by a two-tailed t-test. The proliferative activity was 83 fold higher at 24 hours compared with the control group. The proliferative activity slowed at 36 hours. Mandibular protrusive posturing for 24 hours increased oteonectin mRNA expression 40% in the condyle compared with the corresponding control. After 36 hours of treatment, there was a 60% increase over the corresponding time control. There was an obvious difference of the osteonectin staining between control and treated condylar regions. Microscopic inspection of the treated condyle demonstrated osteonectin staining of proliferating, early hypertraphic chondrocytes, and the chondroid matrix across the sagittal region in an anterior- posterior direction. A gradient intensity from a medial-superior to posterior direction was produced. Quantification of the immunohistochemical data revealed a marked increase immunostaining of the chondroid matrix in treated posterior condyle after 24 hours. The immunostaining lessen in quantity after 36 hours treatment in the chondroid matrix. Unloading of the mouse mandible caused an increased DNA synthesis followed by an increased osteonectin mRNA and then, subsequently, of the osteonectin protein.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact firstname.lastname@example.org.Includes bibliographical references: (leaves 67-73).Thesis (D.Sc.D.)--Boston University Henry M. Goldman School of Graduate Dentistry, 1994.
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