Abstract：
OBJECTIVE: The aim of this study was to understand the temporal and spatial distribution of canonical endochondral ossification (CEO) and non-canonical endochondral ossification (NCEO) of the normal growing rat condyle, and to evaluate their histomorphological changes following the simultaneous hypotrophy of the unilateral masticatory closing muscles with botulinum toxin (BTX).
METHODS: 46 rats at postnatal 4 weeks were used for the experiment and euthanized at postnatal 4, 8, and 16 weeks. The right masticatory muscles of rats in experimental group were injected with BTX, the left being injected with saline as a control. The samples were evaluated using 3D morphometric, histological, and immunohistochemical analysis with three-dimensional regional mapping of endochondral ossifications.
RESULTS: The results showed that condylar endochondral ossification changed from CEO to NCEO at the main articulating surface during the experimental period and that the BTX-treated condyle presented a retroclined smaller condyle with an anteriorly-shifted narrower articulating surface. This articulating region showed a thinner layer of the endochondral cells, and a compact distribution of flattened cells. These were related to the load concentration, decreased cellular proliferation with thin cellular layers, reduced extracellular matrix, increased cellular differentiation toward the osteoblastic bone formation, and accelerated transition of the ossification types from CEO to NCEO.
CONCLUSIONS: The results suggest that endochondral ossification under loading tended to show more NCEO, and that masticatory muscular hypofunction by BTX had deleterious effects on endochondral bone formation and changed the condylar growth vector, resulting in a retroclined, smaller, asymmetrical, and deformed condyle with thin cartilage.
METHODS: 46 rats at postnatal 4 weeks were used for the experiment and euthanized at postnatal 4, 8, and 16 weeks. The right masticatory muscles of rats in experimental group were injected with BTX, the left being injected with saline as a control. The samples were evaluated using 3D morphometric, histological, and immunohistochemical analysis with three-dimensional regional mapping of endochondral ossifications.
RESULTS: The results showed that condylar endochondral ossification changed from CEO to NCEO at the main articulating surface during the experimental period and that the BTX-treated condyle presented a retroclined smaller condyle with an anteriorly-shifted narrower articulating surface. This articulating region showed a thinner layer of the endochondral cells, and a compact distribution of flattened cells. These were related to the load concentration, decreased cellular proliferation with thin cellular layers, reduced extracellular matrix, increased cellular differentiation toward the osteoblastic bone formation, and accelerated transition of the ossification types from CEO to NCEO.
CONCLUSIONS: The results suggest that endochondral ossification under loading tended to show more NCEO, and that masticatory muscular hypofunction by BTX had deleterious effects on endochondral bone formation and changed the condylar growth vector, resulting in a retroclined, smaller, asymmetrical, and deformed condyle with thin cartilage.
摘要：
目的：这项研究的目的是了解正常生长的大鼠髁突的典型软骨内骨化（CEO）和非典型软骨内骨化（NCEO）的时空分布，并评估肉毒杆菌毒素（BTX）同时使单侧咀嚼闭合肌肥大后的组织形态学变化。
方法:将出生后4周的46只大鼠用于实验,并在出生后4、8和16周安乐死。实验组大鼠右侧咀嚼肌注射BTX,左边注射生理盐水作为对照。使用3D形态计量学评估样品，组织学,和免疫组织化学分析与软骨内骨化的三维区域图。
结果：结果表明，在实验期间，髁突软骨内骨化在主要关节表面从CEO转变为NCEO，并且BTX处理的髁表现为后倾的较小髁，前移的较窄关节表面。这个关节区域显示软骨内细胞层较薄，和扁平细胞的紧凑分布。这些与负载浓度有关，细胞增殖减少，细胞层薄，细胞外基质减少，向成骨细胞骨形成的细胞分化增加，加速了骨化类型从CEO到NCEO的过渡。
结论：结果表明，在负荷下软骨内骨化倾向于显示更多的NCEO，BTX引起的咀嚼性肌肉功能减退对软骨内骨形成有有害影响，并改变了髁突生长载体，导致倒退，更小,不对称,软骨薄的髁变形。
方法:将出生后4周的46只大鼠用于实验,并在出生后4、8和16周安乐死。实验组大鼠右侧咀嚼肌注射BTX,左边注射生理盐水作为对照。使用3D形态计量学评估样品，组织学,和免疫组织化学分析与软骨内骨化的三维区域图。
结果：结果表明，在实验期间，髁突软骨内骨化在主要关节表面从CEO转变为NCEO，并且BTX处理的髁表现为后倾的较小髁，前移的较窄关节表面。这个关节区域显示软骨内细胞层较薄，和扁平细胞的紧凑分布。这些与负载浓度有关，细胞增殖减少，细胞层薄，细胞外基质减少，向成骨细胞骨形成的细胞分化增加，加速了骨化类型从CEO到NCEO的过渡。
结论：结果表明，在负荷下软骨内骨化倾向于显示更多的NCEO，BTX引起的咀嚼性肌肉功能减退对软骨内骨形成有有害影响，并改变了髁突生长载体，导致倒退，更小,不对称,软骨薄的髁变形。
