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Fetal Jaw Movement Affects Condylar Cartilage Development
H. Habib1,
T. Hatta2,
J. Udagawa2,
L. Zhang1,3,
Y. Yoshimura1 and
H. Otani2,*
1 Department of Oral and Maxillofacial Surgery,
2 Department of Developmental Biology, Faculty of Medicine, Shimane University, Izumo, Shimane 693-8501, Japan; and
3 present address, University Transgenic Mouse Facility, SUNY at Stony Brook, Stony Brook, NY 11794-8651, USA;
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Figure 1. Exo utero surgery. (A) At E15.5, the abdominal cavity of the dam was surgically revealed, and embryos covered with the embryonic membrane were exposed; then, the mandible and maxilla were fixed by suture, while the umbilical cord and placenta were kept intact inside the amnion. (B) Schematic representation of the suture fixation in (A) performed to restrict fetal jaw movement. (C) Sutured (left) and non-sutured (right) embryos obtained at E18.5. Arrows indicate suture fixation with 8-0 nylon.
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Figure 2. Macroscopic (A,B) and histological (C,D,E,F,G) views of the mandibular condyle of non-sutured (A,C,E) and sutured (B,D,F,G) embryos at E18.5. (A) Non-sutured embryos (10 out of 11) show a clear bone-cartilage margin (arrow) between the condylar head and neck. (B) In contrast, sutured embryos (9 out of 11) show a smaller volume of cartilage with an ill-defined margin (arrow). (C,D) Photomicrographs of the condyle. (C) Non-sutured embryos exhibit a clearly defined junction (arrows) between the cartilage and bone, corresponding to the erosion zone. The boxed area is magnified in E. (D) The hypertrophic zone in the sutured embryos (6 out of 7) had a broader and rounded junction (arrows). The boxed areas are magnified in F and G. The insets in C and D show the junction stained for TRAPase. Fewer osteoclasts (arrowheads) with a strong reaction to TRAPase were observed in the sutured group (insets D vs. C). (E,F,G) Histological changes in the condylar cartilage at E18.5. (E) The condylar cartilage in the non-sutured embryos was subdivided into mesenchymal (M), pre-hypertrophic (P), and hypertrophic (H) zones. (F) In the sutured embryos, the mesenchymal and pre-hypertrophic zones showed fewer and irregularly arranged cell layers. In the pre-hypertrophic zone, the anuclear space led to a discontinuity of the cellular arrangement (arrowheads). The pre-hypertrophic zone appeared to be underdeveloped structurally and was significantly thinner than that of the non-sutured embryos (E). (G) In the sutured embryos (6 out of 7), the acellular structure in the pre-hypertrophic zone was HE-stained in a manner similar to that of bone matrix (arrows). (A,B) Double-staining with alizarin red and alcian blue. (C,D,E,F,G) HE staining. Scale bars: 100 µm.
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Figure 3. Morphometric study of the developing condylar cartilage. Comparison of cartilage volume (A,C), and total number of cells (B,D) between the non-sutured and sutured groups at E16.5 (A, B; N = 3) and E18.5 (C, D; N = 7). (E) BrdU-positive cells and (F) BrdU-labeling indices at E16.5 (N = 3). For the details, see RESULTS. M, mesenchymal zone; P, pre-hypertrophic zone; H, hypertrophic zone;  , non-sutured group;  , sutured group; data are represented as mean ± SD.
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Journal of Dental Research, Vol. 84, No. 5,
474-479 (2005)
DOI: 10.1177/154405910508400514
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