Gene expression in the developing rat mandible: a gene array study

To analyse the molecular events that occur in the developing mandible, gene arrays containing probes for 1176 known genes were used. Total RNA was extracted from the mandibles of 1- and 6-day-old rats. Radiolabeled probes were then synthesised and used to probe the DNA arrays. Of the 1176 genes examined, 306 were detectable, and the latter were analyzed by bioinformatics algorithms. K-means clustering grouped 72 genes into Up, 56 genes into Down and 178 genes into NO change. A large number of genes related to cell receptors (by ligands) were grouped into the Down cluster. Gene array technology appears to be a useful tool for studying the complex process of mandibular development.     

大鼠颌下腺腺病毒介导荧光素酶基因转导及组织学变化

目的 观察大白鼠颌下腺腺病毒介导的荧光素酶基因转导及其组织学变化。方法 将40只Wistar大鼠随机分为5组，经颌下腺导管转导腺病毒介导荧光素酶基因重组体即AdCMVLuc,3d及1、2、4、8周后观察其基因表达及病理变化。结果 颌下腺转基因表达3d时最高，以后逐渐下降，至4周、8周时仍可测到表达。组织病理学变化：3d-1周时可见腺泡受挤压、腺导管扩张；2周时部分腺泡轻度萎缩，腺泡间距离加大；小叶内及小叶间导管周围淋巴细胞呈灶状浸润；4周时可见有腺泡及腺泡腔结构变清晰；8周时腺泡、导管基本恢复正常，炎症不明显。超微结构变化；注入基因后3d，腺泡和导管细胞内可见大量粗面内质网，粘液腺泡中粘液滴增多，融合成片；1周后，导管腔的微绒毛突起减少，胞质内可见线粒体显著增多；2周及4周，腺泡腔可见少量的微绒毛突起及细丝网状物，粘液腺泡中可见粘液滴。基底部可见粗面内质网，基底膜增厚。结论 本研究报道了腺病毒介导的大鼠颌下腺基因转导后的超微结构变化，提示腺体蛋白合成体系功能活跃，大鼠涎腺基因转导能产生生物活性蛋白，腺体有明显炎症反应。     

Effect of protein-energy malnutrition in early life on the dimensions and bone quality of the adult rat mandible.

Morphological and biomechanical features of the mandible are negatively affected by protein-energy malnutrition, whose effects are apparently dependent on the time of life of application. The aim here was to investigate, in neonatal rats nursed by dams put on a protein-free diet to depress milk production and thus create a state of protein-energy malnutrition in the offspring, subsequent growth and long-term effects by analyzing mandibular dimensions and bone quality in adulthood. Pregnant Wistar rats were fed a 20% protein diet (control) or a protein-free diet (malnourished) to obtain normal or subnormal milk production, respectively. After weaning, the offspring (males) were fed a 20% protein diet for 70 days. The dimensions of their excised mandibles were measured directly between anatomical points; the geometry and material quality of mandibular bone were assessed by peripheral quantitative computed tomography. Pups suckling from malnourished dams weighed 49.4% of those suckling from control dams at weaning; the actual difference between control and malnourished pups was 25.1g, which persisted until day 91 of age, indicating the absence of catch-up growth. As with body size, the mandibular base length, height and area (an index of mandibular size) were significantly smaller in malnourished than control rats at the end of the study. The mandibular cortical area, volumetric cortical bone mineral content and volumetric cortical bone mineral density assessed by peripheral quantitative computed tomography were similar in both groups of rats at the end of the observation period, but there was a significant reduction in the cortical axial moment of inertia in malnourished rats at this time of postnatal life. These findings suggest that catch-up growth was incomplete in rats malnourished during the suckling period and that the adaptation of mandibular bone architecture to body growth was apparently insufficient to attain normal values, thus not allowing complete compensation in mechanical competence at the end of the study because of an inadequate spatial distribution of resistive material through its cross-section rather than qualitative or quantitative impairment of cortical bone.     

Degradation of extracellular matrices propagates calcification during development and healing in bones and teeth

BackgroundBone, dentin, and enamel are tissues formed through calcification, a process involving deposition of calcium phosphate minerals on extracellular organic matrices. Calcification, the underlying mechanism of which is unknown, is initiated with mineral deposition followed by advancing of the deposit and subsequent maturation of the mineral crystal.HighlightWe have reviewed the current knowledge of how calcification proceeds during bone development, bone healing, and enamel and dentin development, based on reported studies. Previous studies reported by us and by other authors have suggested that degradation of some extracellular matrix (ECM) proteins is involved in calcification during bone and dentin development and bone healing in a manner similar to that previously reported for enamel development.ConclusionThe ECM proteins may inhibit mineral deposition and calcification, similar to the role of amelogenin during enamel development. The candidates for the amelogenin equivalents in bone and dentin have not been identified. Further studies are required to elucidate the regulatory mechanisms of bone and dentin calcification in light of specific ECM proteins that prevent calcification and enzymes that degrade these ECM proteins.     

uPA和uPAR mRNA在涎腺肿瘤组织中的表达

目的：探讨涎腺肿瘤组织ｕＰＡ及其受体的基因表达和临床意义。方法：应用ｃＤＮＡｍＲＮＡ斑点杂交技术定量检测样品ｕＰＡ和ｕＰＡＲ ｍＲＮＡ含量。结果：良性肿瘤组织ｕＰＡ和ｕＰＡＲｍ ＲＮＡ表达无明显升高。恶性肿瘤级组织ｕＰＡ,ｕＰＡＲ,ｍＲＮＡ含量显著高于相应癌旁组织和良性肿瘤组织;ｕＰＡ,ｕＰＡＲ的表达水平与淋巴结转移关系密切,伴有淋巴结转移和肺转移的癌组织ｕＰＡ,ｕＰＡＲ ｍＲＮＡ含量高于无转移者     

Investigation of the effects of semaphorin 3A on new bone formation in a rat calvarial defect model

Purpose

This study investigates the effects of semaphorin 3A on new bone formation in an experimental rat model.

牙本质基质蛋白1基因敲除鼠的下颌骨和髁突表型特征的初步研究

目的 研究牙本质基质蛋白1(Dmp1)基因敲除(Dmp1-／-)鼠下颌骨和髁突表型特征，探讨Dmp1在骨和软骨形成及矿化中的作用。方法 Dmp1-／-鼠在出生时及出生后2周、2、3、5个月处死并分离下颌骨，行大体观察、X线、透射电镜和组织学观察，比较Dmp1-／-鼠与野生鼠在骨发育、骨密度、组织学上的差异。结果 Dmp1-／-鼠下颌骨和髁突出现骨化不全、密度减低、体积减小和髁突软骨退变等变化。结论 Dmp1是生长板和继发性骨化中心形成的关键因子，在软骨、骨形成和骨结节塑形中发挥重要作用。Dmp1可能是调控下颌骨及髁突软骨发育的候选基因。     

Comparable efficacy of silk fibroin with the collagen membranes for guided bone regeneration in rat calvarial defects

PURPOSE

Silk fibroin (SF) is a new degradable barrier membrane for guided bone regeneration (GBR) that can reduce the risk of pathogen transmission and the high costs associated with the use of collagen membranes. This study compared the efficacy of SF membranes on GBR with collagen membranes (Bio-Gide®) using a rat calvarial defect model.

MATERIALS AND METHODS

Thirty-six male Sprague Dawley rats with two 5 mm-sized circular defects in the calvarial bone were prepared (n=72). The study groups were divided into a control group (no membrane) and two experimental groups (SF membrane and Bio-Gide®). Each group of 24 samples was subdivided at 2, 4, and 8 weeks after implantation. New bone formation was evaluated using microcomputerized tomography and histological examination.

RESULTS

Bone regeneration was observed in the SF and Bio-Gide®-treated groups to a greater extent than in the control group (mean volume of new bone was 5.49 ± 1.48 mm³ at 8 weeks). There were different patterns of bone regeneration between the SF membrane and the Bio-Gide® samples. However, the absolute volume of new bone in the SF membrane-treated group was not significantly different from that in the collagen membrane-treated group at 8 weeks (8.75 ± 0.80 vs. 8.47 ± 0.75 mm³, respectively, P=.592).

CONCLUSION

SF membranes successfully enhanced comparable volumes of bone regeneration in calvarial bone defects compared with collagen membranes. Considering the lower cost and lesser risk of infectious transmission from animal tissue, SF membranes are a viable alternative to collagen membranes for GBR.     

Effects of ovariectomy on turnover of alveolar bone in the healed extraction socket in rat edentulous mandible

Objective

The number of patients with postmenopausal osteoporosis receiving dental implants because of edentulism is increasing. Since osseointegration around implants requires formation and maintenance of new bone, knowledge of how ovariectomy (OVX) affects turnover of mandibular and maxillary bone is required. In the present study, we investigated the effects of OVX on turnover of alveolar bone in the healed extraction socket of the rat left mandibular incisor.

Methods

The molars and the incisor on left side in 6-month-old Sprague–Dawley female rats (n = 38) were extracted and left to heal for 4 months. Animals were then ovariectomized and killed at the time of OVX (baseline) (n = 4), 6 weeks (n = 10), 6 months (n = 12) and 9 months (n = 12) post-OVX. Changes in bone mass and bone turnover were assessed using static and dynamic histomorphometric parameters.

Results

Bone turnover was increased by ovariectomy (OVX) as reflected by increased static parameters of bone formation and resorption. The changes in dynamic parameters were not statistically significant. Cancellous bone volume/total volume (%) in the post-OVX group decreased more than that in the control group.

Conclusions

Our results suggest that OVX increases the turnover of alveolar bone in the healed extraction socket of rat mandibular incisor, resulting in a decrease of cancellous bone volume with time.     

细胞凋亡及其相关基因Bcl-2和 Bax在大鼠正畸牙槽骨改建中的作用

目的：观察大鼠正畸牙齿移动中牙槽骨的细胞凋亡现象以及凋亡相关基因Ｂｃｌ－２和Ｂａｘ的表达,初步探讨细胞凋亡在牙槽骨改建中的作用。方法：选用２５只健康雄性ＳＤ大鼠,用单簧圈别针簧矫治器推上颌切牙侧向移动,于加力后１、３、５、７ｄ系列观察牙槽骨中细胞凋亡及其相关基因Ｂｃｌ－２和Ｂａｘ的表达,以正常组为对照,用免疫组织化学方法和ＴＵＮＥＬ法进行检测。结果：正常牙槽骨组织中存在凋亡细胞,主要见于骨细胞,呈散在性分布,数量较少。牙齿移动时,压力侧牙槽骨改建活跃,凋亡细胞有增多趋势,而张力侧牙槽骨凋亡细胞呈减少趋势。在成骨细胞、破骨细胞、透明性变区未检测到凋亡细胞。Ｂｃｌ－２和Ｂａｘ在正常牙槽骨细胞均有表达,在压力侧Ｂａｘ的表达强于Ｂｃｌ－２,在成骨细胞和破骨细胞Ｂｃｌ－２的表达强于Ｂａｘ。结论：细胞凋亡及其相关基因Ｂｃｌ－２和Ｂａｘ参与了正畸牙齿移动过程中牙槽骨的改建过程。     

Effect of cortical perforations of both graft and host bed on onlay incorporation to the rat skull

The mechanisms involved in the integration of autogeneic bone grafts still attract much interest due to their clinical importance. The purpose of this study was to obtain data on the effects of a combination of cortical bone perforations both at the recipient site and the inner layer of a bicortical graft. 12 adult rats obtained femoral or tibial bicortical bone grafts from isogeneic donors to the tibia, one on each leg. On the experimental side, both the recipient bed and the inner cortical graft layer received multiple perforations (0.25 mm in diameter), while on the control side, only perforations of the recipient cortical bed were made. The findings were assessed by routine histology and immunohistochemical analysis for some bone and cartilage matrix proteins after 4 and 20 weeks. The combined cortical perforations of the graft and the host bed induced a locally improved bony incorporation of the graft and a corticalization of the graft marrow, implying improved mechanical stability. The graft height persistence was similar between groups. Intense labelling of the bone matrix proteins was apparent in all bone tissue and by diversified intensity at its various components, demonstrating ongoing remodeling activities. PRELP and fibromodulin mainly outlined the soft tissues surrounding the graft and compact bone sealing off the graft marrow. Immunolabelling contributed a more delicate picture of the mechanisms involved in graft incorporation.     

Differential expression of LAR tyrosine phosphatase in the rat developing molar tooth germ

OBJECTIVE: This study examined the molecules implicated in the cytodifferentiation of dental hard tissue cells. METHODS: Rat pups at postnatal days 4, 7 and 10 were used. Differential display-polymerase chain reaction (DD-PCR), Western blot and immunofluorescent localisation were performed to search differentially expressed genes in tooth development. RESULTS: Leukocyte-common antigen-related tyrosine phosphatase (lar-tp) was differentially detected between the rat maxillary 2nd and 3rd molar germs on postnatal day 10, which were at the dental hard tissue formation and cap/early bell developmental stages, respectively. Both the mRNA and protein expression levels of lar-tp were higher in the 3rd molar germs than in the 2nd. In addition, the levels in the 2nd molar germs at postnatal days 4, 7 and 10, which corresponded to the early/late bell, crown and root stages, respectively, decreased in a time dependent manner. The immunoreactivity against intracellular P-subunit of lar-tp was detected in the ameloblasts and odontoblasts as well as in the undifferentiated inner enamel epithelia and dental papilla cells. However, strong immunoreactivity against extracellular E-subunit was observed only in the undifferentiated inner enamel epithelia and dental papilla cells in the 3rd molar germs and in the stratum intermedium in the 2nd molar germs. CONCLUSION: This is the first identification of lar-tp in the molar tooth development and suggests that this molecule may be involved in the cytodifferentiation of dental hard tissue cells.     

Radiographic features of a patient with both cemento-ossifying fibroma and keratocystic odontogenic tumor in the mandible: a case report and review of literature

We herein describe a rare case of a 48-year-old woman with both ossifying fibroma (OF) and keratocystic odontogenic tumor (KCOT) in the mandible. CT images showed a 15 × 15 × 20-mm radiolucent-radiopaque lesion with bucco-lingual bony expansion in the left first premolar equivalent area of the mandible, and a 15 × 40 × 35-mm well-defined unilocular radiolucent lesion in the left side of the mandible, extending from the distal side of the distal root of the left second molar to the left mandibular ramus. A biopsy of the radiolucent-radiopaque lesion and fenestration surgery of the radiolucent lesion were performed. Histopathologic examination revealed a fibro-osseous lesion (FOL) and a KCOT, respectively. CT was useful in diagnosing the radiolucent-radiopaque lesion as OF and for detecting the 3-dimensional bone expansion and the contents in the lumen of the KCOT.     

Gene expression and immunohistochemical localization of decorin and biglycan in association with early bone formation in the developing mandible.

We investigated the expression of the small proteoglycans, decorin and biglycan, which are associated with osteoblast differentiation, and how this relates to the expression of osteocalcin and bone sialoprotein (BSP) early in the formation of bone in the rat mandible by immunohistochemistry and in situ hybridization. The mandibles of rat fetuses were collected on embryonic days 14 (E14) to E18. In situ hybridization showed that gene expression of decorin, biglycan, osteocalcin and BSP was not apparent in the developing mandible at E 14, but was expressed by newly differentiated osteoblasts at E15. The expression of these mRNAs increased linearly as the number of osteoblasts increased in specimens from E16 to E18. Immunohistochemistry showed that newly differentiated osteoblasts expressed biglycan moderately, decorin weakly, and osteocalcin and BSP faintly. The unmineralized bone matrices among the osteoblasts showed prominent staining for decorin, weak staining for osteocalcin and BSP, and very weak staining for biglycan. When the intercellular matrix was mineralized at E16, the mineralized bone matrix showed more prominent staining for osteocalcin and BSP, but lacked staining for decorin and biglycan. The same staining profile was observed during the subsequent phases of bone formation at E17 and E18. These results indicate that decorin, biglycan, osteocalcin and BSP are expressed at the gene and protein level by newly differentiated osteoblasts before the onset of matrix mineralization and that they could play a role in the earliest stages of bone formation. Negative proteoglycan staining in the mineralized bone matrix suggests that a loss of, or a sharp decrease in proteoglycans occurs concomitant with bone matrix mineralization.     

雌激素对去势大鼠颌骨和股骨结构影响的实验研究

目的 :观察雌激素对实验性骨质疏松大鼠颌骨和股骨结构影响的相互关系。方法 :切除SD雌性大鼠双侧卵巢建立骨质疏松动物模型 ,给予腹腔注射雌二醇 ,治疗 6周后处死大鼠 ,取颌骨和股骨标本 ,对组织切片进行骨组织形态计量学分析。结果 :去势后的大鼠颌骨、股骨骨小梁呈疏松化改变 ,股骨骨量减少明显多于颌骨 ;雌二醇治疗后可明显抑制颌骨、股骨骨质的吸收 ,颌骨骨量变化更为明显。结论 :雌激素治疗对于骨质疏松的颌骨、股骨骨小梁结构的影响是有差异的 ,治疗效果颌骨优于股骨 ,可能与扁骨、长骨本身结构和功能不同有关     

Role of oxidative and nitrosative stress in autogenous bone grafts to the mandible using Guided Bone Regeneration and a Deproteinized Bovine Bone Material

The aim of this study was to evaluate the role of oxidative and nitrosative stress in autogenous bone grafts to the mandible based on immunohistochemical analysis.Material and methodsUsing a well-established sheep model autogenous bone grafts were harvested form the iliac bone. A combination of a Collagen Membrane (CM) and Deproteinized Bovine Bone Material (DBBM) was used to cover the bone graft (Experiment 2). This modification was compared with simple onlay bone grafts (Experiment 1). Immunohistochemically, the expression of specific stable degradation products of oxidative and nitrosative stress was compared between the two experimental groups.ResultsSpecific markers for oxidative and nitrosative stress showed statistically significant differences in expression in the different experimental groups. The influence of oxidative and nitrosative stress on osteoblasts (OB), osteoclasts (OC), and osteocytes (OCy) was analysed. Experiment 2 showed increased expression of markers in OB and decreased expression in OC.ConclusionsTaking the result of this study and reports from the literature into consideration grafts in Experiment 2 showed less resorption and atrophy, higher activity of OB and inhibition of OC, and less expression of Reactive Oxygen and Nitrogen Species (RONS) as markers of oxidative stress within the graft. These data illustrate the improved remodelling processes in grafts using CM and DBBM.     

周期性牵张力对骨髓破骨细胞MMP-3 mRNA表达的影响

目的 :研究周期性牵张力对成熟破骨细胞MMP 3mRNA表达的影响 ,探讨机械张力与破骨细胞骨基质作用的关系。方法 :实验组从骨髓破骨细胞体外诱导培养的第 7天施加 6周 /min ,弹性基底膜发生 12%形变率的周期性牵张力 ,2 4h后 ,应用原位杂交染色技术检测多核破骨细胞内MMP 3mRNA表达变化情况。结果 :实验组施加周期性牵张力 2 4h后 ,多核破骨细胞MMP 3mRNA阳性信号在所观察视野内染色强度明显增强。结论 :体外周期性牵张力可刺激成熟破骨细胞MMP 3mRNA的表达 ,MMP 3在骨组织应力改建过程中发挥着重要作用。     

Quantitative assessment of post-extraction healing and alveolar ridge remodelling of the mandible in female rats

OBJECTIVE: To quantitatively evaluate the healing and bone changes in the mandible of adult female rats following unilateral extraction of the mandibular molars and the incisor. METHODS: Six-month old female rats had their mandibular molars and the incisor on one side of the mandible extracted. Nine rats were sacrificed at 0, 14, 28, 56 and 112 days post-extraction. Bone mineral density (BMD) as observed by dual energy X-ray absorptiometry (DEXA) and histomorphometric measurements of total bone volume (TBV/TV%) as well as changes in size; height and width on backscattered electron microscopy images of cross-sections of the mandible were evaluated. RESULTS: There was a total increase of 28% in BMD of the body of the mandible and 35.1% increase in TBV/TV% at 112 days post-extraction. A maximal increase of 25% in BMD was observed at 14 days post-extraction. TBV/TV% increased by 9.5% at 14 days post-extraction and further increased by 15.9% (P < 0.001) from 14 to 28 days and by 9.2% (P < 0.001) from 28 to 56 days. A further slight but non-significant increase of 6% (P = 0.108) occurred from 56 to 112 days post-extraction. Regression equations demonstrated that the maximal increase in TBV/TV% and BMD occurred between 0 and 28 days, which subsequently slowed down between 28 and 56 days and further declined between 56 and 112 days post-extraction. Healing was associated with a reduction in cross-sectional area (32.89%), height (21%) and width of the mandible (12.84%). CONCLUSIONS: BMD of the edentulous mandible following extraction of mandibular molars and the incisor on one side of the mandible increases up to 56 days, but that total bone volume increases up to 112 days post-extraction. This indicates that bone volume measurement is more sensitive than BMD measurements in detecting small increase in bone formation at later stages of healing, possibly because of changes in geometry of the edentulous mandible following teeth extraction. The edentulous mandible undergoes a significant reduction in size as a result of reduction in both height and width up to 112 days post-extraction.