不同下颌前伸力对髁突Runx2和X型胶原表达的影响

目的:探讨不同作用方式的下颌前伸力对髁突软骨内成骨的影响.方法:将28只5周龄雄性wistar大鼠随机分配到周期性、静止性、功能性下颌前伸组及阴性对照组(n=7).各组按照设定的相关参数接受下颌前伸力刺激.实验结束时取标本,免疫组织化学染色,对Runx2、X型胶原的表达进行半定量分析.结果:Runx2和X型胶原表达动态组最高(与对照组比P＜0.01),静态组和功能组较低(与对照组比P＜0.01).静态组X型胶原表达高于功能组(P＜0.01),Runx2表达静态组与功能组差异无显著性(P＞0.05).结论:不同作用方式及作用时间的下颌前伸力差异性调节髁突软骨细胞Runx2及X型胶原的表达水平.     

Facial development disorders due to inhibition to endochondral ossification of mandibular condyle process caused by malnutrition

Objective:To analyze the effect of protein restriction on histomorphometric parameters of bone remodeling in mandibular condyle process and its possible influence in facial development in growing rats.Materials and Methods:Wistar rats weaned at the age of 21 days were assigned to one of the following groups: control (fed a regular hard diet ad libitum) and protein restricted (PR) (fed a hard diet lacking in protein ad libitum). The animals were euthanized on day 35 after the onset of the experiment. Mandibles were resected, fixed in 10% formalin, hemisected at the symphysis, and then radiographed in order to perform cephalometric studies of the condylar process length and the height of the lower alveolar process. Mandibles were then processed for light microscopy, and histomorphometric determinations were performed on histologic sections of the condylar process subchondral bone.Results:The PR group showed a significantly lower body weight than control group at the end of the experiment. The length of the condylar process was lower in the PR group; however, the diet used in this study did not affect the height of the lower alveolar process. The histomorphometric analysis showed that the PR group exhibited a statistically significant decrease in bone formation and bone volume in condylar process subchondral bone.Conclusion:Protein restriction inhibits bone formation and longitudinal growth in the mandibular condylar process. This result suggest that protein restriction can alter normal facial development.     

Neovascularization and bone formation in the condyle during stepwise mandibular advancement

The aims of this investigation were to identify the temporal expression of vascular endothelial growth factor (VEGF) in the mandibular condyle and to correlate it with the pattern of new bone formation during stepwise mandibular advancement. Two hundred and fifty female, 35-day-old Sprague-Dawley rats were randomly divided into 10 groups, with 10 rats allocated to the single-step bite-jumping subgroup, 10 rats to the stepwise advancement subgroup and five rats to the control subgroup. In the experimental groups, the mandibles were kept in a continuous forward position. The initial stepwise advancement commenced on day 35, whereas the second advancement started on day 65. The rats were sacrificed on experimental days 3, 7, 14, 21, 30, 33, 37, 44, 51 and 60. Sections (7 microm) were cut through the condyle in the parasagittal plane and stained with anti-VEGF antibody. Each section was counter-stained with haematoxylin for observation of the cellular response. The sections were digitized and quantitatively analysed with a computer-assisted image analysing system. The results showed that the initial advancement in the stepwise group led to significantly less expression of VEGF when compared with single advancement. However, the second advancement on day 30 resulted in a significant increase in VEGF expression when compared with the one-step group and the natural growth control group. Thus, it was concluded that changes in the amplitude of mechanical loading, produced by stepwise advancement, have a significant effect on the production of VEGF by the chondrocytes. During the later stages of advancement, more VEGF and more condylar bone was produced.     

Forward deviation of the mandibular condyle enhances endochondral ossification of condylar cartilage indicated by increased expression of type X collagen

OBJECTIVE: Using type X collagen as a marker, this research was designed to examine the alteration of condylar growth in response to mandibular condylar forward positioning. METHODS: One hundred female Sprague-Dawley rats with 5 weeks of age were randomly divided into five experimental and five control groups. In the experimental groups, bite jumping appliances created forward positioning of the condyle. The experimental rats, together with the age-matched controls, were sacrificed on days 3, 7, 14, 21 and 30, respectively. Tissue sections were cut in the sagittal plane through the mandibular condyle and were processed for in situ hybridization and immunostaining of type X collagen and then for quantitative imaging analyses. RESULTS: (1) Both type X collagen mRNA in situ hybridization signals and type X collagen immunostaining were localized within the hypertrophic zone of the condylar cartilage. (2) With condylar forward positioning, the level of type X collagen mRNA signals (8,541 +/- 74 microm(2) at peak) was 300% higher than that in the controls (2,117 +/- 78 microm(2) at peak); type X collagen immunostaining in condylar advancing groups (54,864 +/- 134 microm(2) at peak) was 254% more than that in the controls (15,470 +/- 121 microm(2) at peak). (3) The amount of type X collagen mRNA signals and immunostaining in experimental and control groups reached the highest levels at day 14 and day 21, respectively, indicating that an increase in endochondral ossification occurred 21 days after condylar forward deviation. CONCLUSION: Condylar forward repositioning provokes an enhanced maturation of condylar chondrocytes resulting in increased synthesis of type X collagen, a extracellular protein that attributes to endochondral ossification.     

Fgf9在小鼠下颌骨发育软骨成骨及膜内成骨过程中的作用探讨

目的:观察成纤维细胞生长因子9(fibroblast growth factor 9,Fgf9)基因敲除小鼠模型中下颌骨发育的骨质变化,探讨Fgf9参与下颌骨发育中的软骨成骨和膜内成骨的过程.方法:建立Fgf9基因敲除小鼠模型(Fgf9-/-).利用显微CT技术检测Fgf9-/-的下颌骨形态及骨参数,利用原位杂交对Fg...     

Osteoma in mandibular condyle

A case of peripheral osteoma occurring in the mandibular ramus in a 26-year-old man is reported. Radiographic examination revealed a pedunculated, protruding globular, bone-like opaque mass around the notch of the right mandibular ramus. Histopathological examination showed a lamellar bone structure with irregular arrangement. Wide trabeculae, narrow interstitial areas, and many fibrovascular channels were detected by scanning electron microscopy. Thus, characteristic findings of a compact osteoma were obtained clinically and histopathologically.     

Motion of the human mandibular condyle during mastication

It has been reported that loading to the mandible during closing movement makes the condylar path move more in the superior direction than that during the free closing movement. In this study, the hypothesis was tested that the displacement of the condyle on the chewing side is greater in the direction of the mandibular fossa than that on the non-chewing side. Using a six-degrees-of-freedom jaw movement recording system, we recorded condylar motion in 12 healthy adults without TMD, during the chewing of a large hard gummy jelly. The maximum displacements at the condyle on the chewing side from the maximum intercuspation (CO) position were significantly larger in the superior and medial directions at the initial stage and in the posterior direction at all stages (0.5 mm, 0.5 mm, and 0.6 mm, respectively) than those on the non-chewing side (0.0 mm, 0.1 mm, and 0.1 mm, respectively). This suggests that, in healthy adults, the condyles at CO are located in a position such that excessive load is not applied to the temporomandibular joint when there are the aforementioned displacements.     

Ihh-PTHrP负反馈信号通路对髁突软骨内成骨作用的研究现状

临床研究发现,颌面部发育畸形的患者,尤其是Ⅱ类错患者,常同时伴有颞下颌关节盘前移位,而青少年期颞下颌关节盘前移位与颌面部发育畸形存在密切关系。其原因可能与关节盘移位导致髁突表面的应力分布发生改变有关,但具体机制尚不明确。印度豪猪蛋白(Ihh)-甲状旁腺相关蛋白(PTHrP)信号通路是调节骨骺生长板软骨细胞增殖、分化、肥大和矿化的重要负反馈轴,在软骨内成骨中发挥着关键的作用。同时,Ihh是机械应力信号向生物信号转导的重要媒介,介导机械应力信号向刺激软骨生长的生物信号转化。本文对Ihh-PTHrP负反馈信号通路对下颌骨髁突软骨内成骨作用的研究现状作一综述。     

Influence of growth hormone and thyroxine on endochondral osteogenesis in the mandibular condyle and proximal tibial epiphysis.

Interrelationships of growth hormone and thyroxine effects on endochondral osteogenesis have been investigated. Evidence is offered that thyroxine augments the effect of growth hormone on the mandibular condyle just as at other osteogenetic centers, for example proximal tibial epiphysis in hypophysectomized rats. This contrasts with previous reports of a unique thyroxine antagonism to the effect of growth hormone on condylar development. In a further study on tibial epiphysis, special attention was given to assure absence of the endogenous thyroid hormone by adding thyroidectomy to hypophysectomy and reducing the possibility of thyroteopin residues in growth hormone. By histochemical tests, the responses of both calcified and noncalcified regions of the epiphyseal cartilage plate were measured. Graded growth hormone doses stimulated graded response in a noncalcified region. Thyroxine augmented this response eightfold. The width of the calcified region of the plate did not vary with treatment.     

Factors regulating endochondral ossification in the spheno-occipital synchondrosis

OBJECTIVES: To identify the temporal pattern of core-binding factor alpha1 (Cbfa1) and vascular endothelial growth factor (VEGF) expressions in the spheno-occipital synchondrosis in vitro with and without tensile stress. MATERIALS AND METHODS: Sixty male BALB/c mice were randomly divided into an experimental group (with tensile stress) and a control group (without tensile stress) at each of five time points. Animals were sacrificed and the cranial base synchondroses were aseptically removed. In the experimental groups, mechanical stress was applied on the surgical explants with helical springs and incubated as organ culture for 6, 24, 48, 72, and 168 hours. In the control group, the springs were kept at zero stress. Tissue sections were subjected to immunohistochemical staining for quantitative analysis of Cbfa1 and VEGF expression. RESULTS: Quantitative analysis revealed that Cbfa1 and VEGF expressions reached a peak increase at 24 and 48 hours, respectively. Compared with the control groups, both Cbfa1 and VEGF were expressed consistently higher in the experimental groups at all time points. CONCLUSION: Mechanical stress applied to the spheno-occipital synchondrosis elicits Cbfa1 expression and subsequently up-regulates the expression of VEGF. Increased levels of expression of both factors could play a role in the growth of the spheno-occipital synchondrosis.     

软骨内成骨修复骨损伤的调节机制

软骨内成骨是主要的骨修复方式之一,它遵循特定的生物学步骤,并涉及复杂的调节机制。近年来,基于软骨内成骨模型开展的骨再生研究日益增多,全面了解其发生机制可以为骨再生的研究提供重要依据。因此,本文对近期软骨内成骨修复骨损伤的调节机制做一综述。     

The correlation of replicating cells and osteogenesis in the condyle during stepwise advancement

The aim of this study was to quantify the number of replicating mesenchymal cells and to correlate it to the amount of bone formation in the condyle during stepwise advancement of the mandible. Two hundred and fifty female Spraque-Dawley rats, 35 days old, were randomly divided into 10 control groups (n = 5) and 20 experimental groups (n = 10). Fifty rats from the stepwise experimental group relieved a two-mm advancement initially and veneers were added on day 30 with another 1.5 mm advancement. The rats were sacrificed after 3, 7, 14, 21, 30, 33, 37, 44, 51, and 60 days. One hour before death, all rats were injected with bromodeoxyuridine (BrdU) intravenously. Tissue sections of seven microm were cut through the condyle in the sagittal plane and stained with anti-BrdU antibody to evaluate the number of replicating mesenchymal cells. Haematoxylin stain was applied to observe cellular response. The results indicated that during the first advancement, replicating mesenchymal cells in the posterior region of the condyle showed the highest increase on days 7 and 14 when compared with the control. Such an increase preceded the highest level of bone formation between days 30 and 37 of advancement. In response to the second advancement, another increase of replicating cells was evident on day 44, along with a significant increase in bone formation observed on day 60. We concluded that forward positioning of mandible in a stepwise manner delivers a mechanical strain that solicits an increase in the number of replicating mesenchymal cells in the condyle. The increase in the population size of the osteoprogenitor cells subsequently leads to more bone formation.     

Osteoid osteoma in mandibular condyle.

A 21-year-old Japanese woman presented with trismus and spontaneous pain (especially at night) around the left temporomandibular joint. Radiographic examination showed a subcortical sclerosed nodule measuring approximately 8 mm in diameter on the infero-lateral aspect of the left mandibular condyle. Amputation of the condyle was performed under general anesthesia. The patient has been in good condition 8 years postoperatively. The histopathology of the specimen consisted of actively proliferating osteoblasts mixed with an interlacing network of woven bone and osteoid trabeculae. Histopathological diagnosis was osteoid osteoma.     

Skeletal stability after mandibular advancement in bilateral sagittal split osteotomies during adolescence

Bilateral sagittal split osteotomy (BSSO) is the most frequently performed surgery for correcting mandibular retrognathia. Few studies have reported the use of BSSO in young patients, as growth may cause relapse. The aim of the present study was to determine the amount of relapse after performing BSSO in patients aged less than 18 years. Patients who had a mandibular advancement by BSSO surgery between January 2003 and June 2008 were evaluated. Eighteen patients were treated before the age of 18 years and compared with patients treated at 20–24 years of age. Cephalometric radiographs were used to determine the amount of relapse. For patients aged less than 18 years, the mean horizontal relapse after 1 year was 0.5 mm, (10.9% of perioperative advancement). For patients aged 20–24 years, the mean relapse was 0.9 mm, (16.4% of perioperative advancement). There were no significant differences between the age groups (p > 0.05). In conclusion, the BSSO procedure is a relatively stable procedure, even during adolescence.     

Distribution and characterization of proliferative cells in the rat mandibular condyle during growth

Distribution of proliferative cells and localization of types I and II collagen were examined in the rat mandibular condylar cartilage of 36 long-Evans/Turku strain rats during normal postnatal growth using an immunohistochemical method combined with histomorphometry. There were considerable differences in the thickness of the proliferative cell layer in the condylar head, with most mitoses occurring in the postero-superior area. It was found that the extracellular matrix of the proliferative cells does not stain for type II collagen in 20-day-old and older rats, and that besides the subchondral bone, the strongest intensity for type I collagen stain was always localized in the articular surface of the condylar head. Statistically significant overlapping of the proliferative cell layer and the one secreting type II collagen occurred during the earlier stages of development, particularly in the postero-superior area of the condylar head. As type II collagen is considered to be a marker for identification of typical cartilage cells, the findings indicate that, in addition to undifferentiated cells, a portion of the proliferative cells can be characterized as chondroblasts during the early postnatal period in rats, but not in the later stages of development. The developmental phase of the condylar cartilage should therefore be taken into consideration when the effect of various biomechanical and humoral/hormonal factors on growth of the condylar cartilage is examined.