去势大鼠骨组织中OPG、VEGF在雌激素治疗前后的变化

目的 制备去卵巢大鼠骨质疏松模型,比较去势6、8周后胫骨上VEGF mRNA、OPG的表达,及雌激素治疗后的变化.方法 53只6月龄的SD雌性大鼠随机分成3组:ovx组(去势组),sham组(假手术组),ovx+E2组(雌激素治疗组);分别在去势后6周末和8周末股动脉放血处死大鼠,每组各8只.取右侧胫骨脱钙后,行组织形态学观察及VEGF原位杂交和OPG免疫组化镜下观察.结果 去势6周和8周后,可见:(1)OPG蛋白表达情况:①OPG阳性细胞主要表达在大鼠胫骨的关节软骨细胞,骺板肥大区软骨细胞,及骺板下初级骨小梁的黏合线上.成骨细胞和骨细胞呈弱阳性表达.骨髓腔间充质细胞表达弱或没有表达,巨核细胞可有弱阳性的表达;②与sham组相比, ovx组中关节软骨细胞,骺板肥大区软骨细胞阳性表达有升高趋势;③与ovx组相比,ovx+E2组关节软骨细胞,骺板肥大区软骨细胞阳性表达有升高趋势;(2)VEGF mRNA表达情况:①VEGF mRNA阳性细胞主要表达于关节软骨细胞、骺板肥大区细胞和增生区细胞、成骨细胞和骨细胞及骨髓间充质细胞和巨核细胞、皮质外侧的成纤维细胞;②与sham组相比, ovx组骺板肥大区软骨细胞、关节软骨细胞、骨髓间充质细胞阳性表达有升高趋势;③与ovx组相比,ovx+E2组关节软骨、骺板肥大区软骨细胞阳性信号有降低趋势;骨髓间充质细胞的阳性信号有升高趋势.结论 (1)去势后雌激素降低,骨重建加强,骨吸收和骨形成均增加,OPG一过性升高可调节破骨细胞的募集和形成.雌激素治疗后OPG表达增高提示OPG可能具有一定的雌激素依赖性.(2)去势后雌激素降低,VEGF生成增多,并参与到骨的血管形成过程中,参与骨丢失.VEGF可能作为破骨细胞的诱导物,促使破骨细胞形成.给予雌激素治疗后,雌激素可使VEGF参与血管形成过程,调节成骨细胞的骨形成过程.     

骨质疏松症中miRNA调控骨种子细胞分化的研究

骨质疏松症与骨稳态失衡密切相关。骨稳态主要由骨种子细胞(成骨细胞、破骨细胞、间充质干细胞、单核/巨噬细胞)维持,可受多种信号通路调控。近年来微小RNA(miRNA)被证实在改善骨质疏松症方面的疗效,可能通过多种途径调控骨种子细胞的分化。该文拟对骨质疏松症中miRNA调控骨种子细胞分化的研究进展进行综述。     

表皮生长因子受体信号通路对骨折愈合的生物学作用

骨折愈合过程中,骨髓间充质干细胞、软骨细胞、成骨细胞及破骨细胞都有各自特定的作用,任何一类细胞的功能异常都会影响骨折愈合。目前一些研究显示,EGFR信号通路参与调节骨髓间充质干细胞、软骨细胞、成骨细胞及破骨细胞的增殖、分化及凋亡等多种生物学过程,在此,作者对EGFR信号通路对骨折愈合过程中相关骨组织细胞的影响做一综述。     

不同氧环境中破骨细胞的发育分化和功能变化研究

目的 本实验拟观察不同氧浓度下破骨细胞诱导过程中的分化发育,寻找破骨细胞体外培养的适宜氧浓度,为骨转换平衡的修复提供依据.方法 取野生型C57B/L小鼠(2个月龄左右,雄性)骨髓进行破骨细胞的诱导培养.用RANKL(10ng/ml)和M-CSF(10ng/ml)联合的诱导方案,将小鼠骨髓中单核-巨噬细胞系体外诱导为破骨细胞样细胞.将原代破骨细胞置于20%O2、7%O2、2%O2下诱导培养,MOCP5不同氧浓度下普通培养.用MTT法检测MOCP5的增殖变化,用抗酒石酸酸性磷酸酶(TRAP)染色检测破骨细胞形成的变化,并进行TRAP阳性细胞计数,用象牙骨片骨吸收陷窝甲苯胺蓝染色检测破骨细胞骨吸收活性的变化.结果 骨髓中单核-巨噬细胞体外经RANKL和M-CSF联合诱导可分化为多核的破骨细胞样细胞,在诱导第3天细胞开始融合,第5天TRAP染色强阳性,第8天可见象牙骨片上形成圆形、椭圆形、腊肠形等多种形态的骨吸收陷窝.MTT检测显示MOCP5在20%O2培养时一直处于增殖状态,7%O2条件下由增殖期进入平台期,2%O2时增殖缓慢且没有规律.20%O2、7%O2、2%O2培养下形成的TRAP阳性破骨细胞数分别为22±5.97、34±2.97、7±1.39(P<0.05),原代诱导的破骨细胞在20%O2、7%O2、2%O2形成的骨吸收陷窝面积(μm2)分别为3892.28±1642.78、5356.7±1655.6、2573±994.48(P<0.05).结论 体外RANKL和M-CSF联合可将骨髓单核-巨噬细胞诱导成多核的破骨细胞样细胞作为破骨细胞的研究模型.常氧条件下破骨细胞的TRAP阳性细胞数和骨吸收活性均低于7%O2.7%O2培养下的破骨细胞更接近于体内生理状态的破骨细胞.     

未分化间充质细胞成骨作用的研究进展

未分化间充质细胞成骨作用的研究进展王立平党耕町在骨组织损伤后的修复过程中,正常骨愈合的条件是多方面的,而生骨细胞来源是重要条件之一。诸多研究表明,骨膜、骨髓为生骨细胞的重要来源,其中有能直接分化为成骨细胞和软骨细胞的未分化间充质细胞（ｍｅｓｅｎｃｈｙ...     

Notch信号通路调控软骨内成骨的研究现状

脊椎动物的骨骼形成是一个复杂的过程。从间充质细胞的富集、体节的形成、软骨内成骨或膜内成骨到骨骼的钙化,软骨细胞、成骨细胞和破骨细胞之间总是存在功能的平衡。软骨内成骨作为骨骼形成的一种主要方式,受多种因素的影响,Notch通路在该过程中起到了极其重要的作用。     

诱导小鼠破骨前体细胞成熟分化的实验条件探讨

目的探讨小鼠单核细胞RAW264.7能否在RANKL诱导下向破骨细胞成熟分化。方法 RANKL作用RAW264.7细胞7天～9天,光镜、透射电镜、扫描电镜(scanning electron microscope,SEM)分别观察其细胞形态学变化,用抗酒石酸酸性磷酸酶(tartrate-resistant acid phosphatase,TRAP)染色法观察TRAP阳性的多核细胞,RT-PCR检测破骨细胞表型和功能基因表达变化情况,扫描电镜观察破骨细胞在骨片上形成骨吸收陷窝。结果光镜、透射电镜下可见细胞胞体增大,为椭圆形或不规则形,胞核5～10个,扫描电镜下可见细胞表面大量的伪足样突起;此外,RANKL能诱导RAW264.7细胞分化为TRAP染色阳性的多核破骨细胞,细胞多为超过5个核的多核巨细胞;RAW264.7细胞成熟分化后具有骨吸收功能,并且能上调Cathepsin-K、TRAP、RANK等典型破骨细胞表型和功能基因mRNA的表达。结论 RAW264.7细胞是一种较好的破骨前体细胞模型,单用50ng/ml的RANKL体外连续诱导7天以上,能明显促进它向成熟的破骨细胞分化。     

不同代数骨髓源性巨噬细胞增殖及诱导破骨分化的规律研究

目的 探讨不同代数骨髓源性巨噬细胞增殖及诱导破骨分化的规律。方法 选取8周龄C57BL/6小鼠P0~P4共5代骨髓源性巨噬细胞,随机选择镜下视野计数杂质细胞与衰老细胞;运用CCK8法检测骨髓源性巨噬细胞的增殖能力;诱导巨噬细胞破骨分化,通过抗酒石酸酸性磷酸酶染色量化破骨细胞数量与破骨细胞面积,比较不同代数之间指标差异。 结果 P0组、P1组骨髓源性巨噬细胞的杂质较P2组、P3组、P4组更多,且差异有统计学意义;96 h内,P2组骨髓源性巨噬细胞的增殖能力最强,P3组、P4组次之,P0组、P1组最差;诱导破骨分化后,P2组骨髓源性巨噬细胞诱导出破骨细胞数量最多,面积最大,P3组次之,P0组、P1组、P4组诱导出破骨细胞数量少,面积小。结论 P2组骨髓源性巨噬细胞的纯度最高,增殖速度最快,破骨分化能力最强。     

雌激素通过调节 EphB4／EphrinB2信号参与破骨细胞分化

目的研究雌激素通过调节EphB4/EphrinB2信号通路对破骨细胞分化的影响。方法 (1)采用RANKL诱导法培养卵巢摘除骨质疏松模型(OVX)组和假手术(Sham)组小鼠的破骨细胞,于第10天提取两组细胞的RNA和蛋白质样品,通过RT-PCR和Western blot检测细胞EphrinB2表达的变化;(2)采用雌激素及雌激素拮抗剂分别诱导培养RAW264.7破骨细胞,培养第8天提取RNA和蛋白质样品,利用RT-PCR和Western blot检测细胞EphrinB2表达的变化;(3)在OVX模型组小鼠的破骨细胞培养中添加EphrinB2配体EphB4-Fc片段,通过RT-PCR检测破骨细胞标志物的表达和抗酒石酸酸性磷酸酶(TRAP)染色并计数,观察破骨细胞分化能力的变化。结果卵巢摘除骨质疏松模型组小鼠EphrinB2的表达量低于假手术组(P0.01);雌激素拮抗剂组EphrinB2的表达量低于对照组(P0.01),而雌激素组EphrinB2的表达量高于对照组(P0.05);给予EphrinB2的配体EphB4-Fc片段后,OVX组小鼠的破骨细胞标志物表达量降低(P0.01,P0.001),TRAP染色阳性细胞数减少。结论雌激素可以通过调节破骨细胞EphrinB2的表达影响破骨细胞分化,采用EphB4-Fc片段处理后,OVX组小鼠增强的破骨细胞分化受到抑制。     

破骨细胞形成过程中的融合与分裂

 目的 研究破骨细胞的形成及其特殊细胞生物学行为。方法 采用活细胞成像技术连续动态观察大鼠周围血单核细胞在核因子κB 受体激活物配体(receptor activator of NF-κB ligand, RANKL)和巨噬细胞集落刺激因子 (macrophage colony stimulating factor,M-CSF)诱导下向破骨细胞分化及形成具有骨吸收功能的多核细胞的全过程。采用倒置相差显微镜观察、抗酒石酸酸性磷酸酶染色、骨磨片扫描电镜观察法对破骨细胞进行鉴定。结果 细胞诱导培养2周后,倒置相差显微镜观察可见大量多核细胞形成;抗酒石酸酸性磷酸酶染色显示绝大部分多核细胞与单核细胞均呈阳性反应;骨磨片扫描电镜观察可见较多的骨吸收陷窝、坑洼、沟道及破骨细胞。活细胞成像观察表明多核破骨细胞是由单核细胞、单核细胞与多核细胞及多核细胞之间相互融合而成,其细胞间的融合均发生在贴壁状态;显微缩时电影观察显示破骨细胞形态复杂多变,多核破骨细胞可以发生分裂。结论 大鼠周围血单核细胞在RANKL和M-CSF诱导下可向破骨细胞分化,形成具有骨吸收功能的破骨细胞。破骨细胞能够通过多种方式融合形成巨大的多核细胞,使其核数增加、体积增大、形态伸缩多变、质膜贴附面积广泛扩展,同时破骨细胞还可通过分裂来缩小体积、减少核数,以适应局部形态学、生物力学及骨吸收动力学的需求。这提示破骨细胞的融合及非有丝分裂方式可能是其发挥功能效应与骨吸收效率的一种特殊细胞生物学行为。     

Expression of parathyroid hormone-related peptide and insulin-like growth factor I during rat fracture healing.

Parathyroid hormone-related peptide (PTHrP) and insulin-like growth factor I (IGF-I) are both involved in the regulation of bone and cartilage metabolisms and their interaction has been reported in osteoblasts. To investigate the interaction of PTHrP and IGF-I during fracture healing, the expression of mRNA for PTHrP and IGF-I, and receptors for PTH/PTHrP and IGF were examined during rat femoral fracture healing using an in situ hybridization method and an immunohistochemistry method, respectively. During intramembranous ossification, PTHrP mRNA, IGF-I mRNA and IGF receptors were detected in preosteoblasts, differentiated osteoblasts and osteocytes in the newly formed trabecular bone. PTH/PTHrP receptors were markedly detected in osteoblasts and osteocytes, but only barely so in preosteoblasts. During cartilaginous callus formation, PTHrP mRNA was expressed by mesenchymal cells and proliferating chondrocytes. PTH/PTHrP receptors were detected in proliferating chondrocytes and early hypertrophic chondrocytes. IGF-I mRNA and IGF receptor were co-expressed by mesenchymal cells, proliferating chondrocytes, and early hypertrophic chondrocytes. At the endochondral ossification front, osteoblasts were positive for PTHrP and IGF-I mRNA as well as their receptors. These results suggest that IGF-I is involved in cell proliferation or differentiation in mesenchymal cells, periosteal cells, osteoblasts and chondrocytes in an autocrine and/or paracrine fashion. Furthermore, PTHrP may be involved in primary callus formation presumably co-operating with IGF-I in osteoblasts and osteocytes, and by regulating chondrocyte differentiation in endochondral ossification.     

A computational model of clavicle bone formation: A mechano-biochemical hypothesis

Clavicle development arises from mesenchymal cells condensed as a cord extending from the acromion towards the sternal primordium. First two primary ossification centers form, extending to develop the body of the clavicle through intramembranous ossification. However, at its ends this same bone also displays endochondral ossification. So how can the clavicle be formed by both types of ossification? Developmental events associated with clavicle formation have mainly used histological studies as supporting evidence. Nonetheless, mechanisms of biological events such as molecular and mechanical effects remain to be determined.The objective of this work was to provide a mathematical explanation of embryological events based on two serial phases: first formation of an ossified matrix by intramembranous ossification based on three factors: systemic, local biochemical, and mechanical factors. After this initial phase expansion of the ossified matrix follows with mesenchymal cell differentiation into chondrocytes for posterior endochondral ossification. Our model provides strong evidence for clavicle formation integrating molecules and mechanical stimuli through partial differentiation equations using finite element analysis.     

Midkine is expressed during repair of bone fracture and promotes chondrogenesis.

Midkine (MK) is a heparin-binding growth/differentiation factor implicated in the control of development and repair of various tissues. Upon fracture of the murine tibia, MK was found to be transiently expressed during bone repair. MK was immunohistochemically detected in spindle-shaped mesenchymal cells at the fracture site on day 4 after fracture and in chondrocytes in the area of endochondral ossification on day 7. MK expression was decreased on day 14 and scarcely seen on day 28 when bone repair was completed. This mode of MK expression is reminiscent of MK expression during development. MK was expressed in hypertrophic chondrocytes of the prebone cartilage rudiments on embryonic day 14 in mouse embryos. MK was also strongly expressed in the epiphyseal growth plate. MK was localized intracellularly during both bone repair and development, and this localization was confirmed by immunoelectron microscopy for embryonic chondrocytes. When MK cDNA was transfected into ATDC5 chondrogenic cells and overexpressed, the majority of transfected cells with strong MK expression showed enhanced chondrogenesis as revealed by increased synthesis of sulfated glycosaminoglycans, aggrecan, and type II collagen. These results suggest that MK plays important roles in chondrogenesis and contributes to bone formation and repair.     

The role of endothelial‐mesenchymal transition in heterotopic ossification

Heterotopic ossification (HO) is a process by which bone forms in soft tissues, in response to injury, inflammation, or genetic disease. This usually occurs by initial cartilage formation, followed by endochondral ossification. A rare disease called fibrodysplasia ossificans progressiva (FOP) allows this mechanism to be induced by a combination of genetic mutation and acute inflammatory responses. FOP patients experience progressive HO throughout their lifetime and form an ectopic skeleton. Recent studies on FOP have suggested that heterotopic cartilage and bone is of endothelial origin. Vascular endothelial cells differentiate into skeletal cells through a mesenchymal stem cell intermediate that is generated by endothelial‐mesenchymal transition (EndMT). Local inflammatory signals and/or other changes in the tissue microenvironment mediate the differentiation of endothelial‐derived mesenchymal stem cells into chondrocytes and osteoblasts to induce HO. We discuss the current evidence for the endothelial contribution to heterotopic bone formation. © 2012 American Society for Bone and Mineral Research.     

The Role of Chondrocytes in Intramembranous and Endochondral Ossification During Distraction Osteogenesis in the Rabbit

We have used a rabbit leg-lengthening model for detailed studies of the histology of distraction osteogenesis. Some unusual features of the endochondral ossification that occurs during the rapid transition of cartilage to bone in the regenerate were observed. Histological staining techniques together with immunohistochemistry and nonradioactive in situ mRNA hybridization for cartilage and bone-related molecules have been used to document the presence of an overlapping cartilage-bone phenotype in cells of the cartilage-bone transitional region. In those particular areas, some chondrocytes appeared to be directly transformed into newly formed bone trabeculae which are surrounded by bone matrix. Acid phosphatases were found within the cartilage matrix in some of the cartilage/bone transitional regions and type I collagen mRNA and type II collagen protein were found together in some of the marginal hypertrophic chondrocytes. This study indicates an unusual role of chondrocytes in the process of ossification at a distraction rate of 1.3 mm/day in the rabbit. Further direct evidence is required to prove the hypothesis that the hypertrophic chondrocytes may transdifferentiate into bone cells in this model. Received: 13 March 1997 / Accepted: 22 September 1998     

Distinct and Overlapping Patterns of Localization of Bone Morphogenetic Protein (BMP) Family Members and a BMP Type II Receptor During Fracture Healing in Rats

Bone morphogenetic proteins (BMPs) and their receptors (BMPRs) are thought to play an important role in bone morphogenesis. The purpose of this study was to determine the locations of BMP-2/-4, osteogenic protein-1 (OP-1, also termed BMP-7), and BMP type II receptor (BMPR-II) during rat fracture healing by immunostaining, and thereby elucidate the possible roles of the BMPs and BMPR-II in intramembranous ossification and endochondral ossification. In the early stage of fracture repair, the expression of BMP-2/-4 and OP-1 was strongly induced in the thickened periosteum near the fracture ends, and coincided with an enhanced expression of BMPR-II. On day 7 after fracture, staining for BMP-2/-4 and OP-1 immunostaining was increased in various types of chondrocytes, and was strong in fibroblast-like spindle cells and proliferating chondrocytes in endochondral bone. On day 14 after fracture, staining with OP-1 antibody disappeared in proliferating and mature chondrocytes, while BMP-2/-4 staining continued in various types of chondrocytes until the late stage. In the newly formed trabecular bone, BMP-2/-4 and OP-1 were present at various levels. BMPR-II was actively expressed in both intramembranous ossification and endochondral ossification. Additionally, immunostaining for BMP-2/-4 and OP-1 was observed in multinucleated osteoclast-like cells on the newly formed trabecular bone, along with BMPR-II. In reference to our previous study of BMP type I receptors (BMPR-IA and BMPR-IB), BMPR-II was found to be co-localized with BMPR-IA and BMPR-IB. BMP-2/-4 and OP-1 antibodies exhibited distinct and overlapping immunostaining patterns during fracture repair. OP-1 may act predominantly in the initial phase of endochondral ossification, while BMP-2/-4 acts throughout this process. Thus, these findings suggested that BMPs acting through their BMP receptors may play major roles in modulating the sequential events leading to bone formation.     

Epiphyseal Chondrocyte Secondary Ossification Centers Require Thyroid Hormone Activation of Indian Hedgehog and Osterix Signaling

Thyroid hormones (THs) are known to regulate endochondral ossification during skeletal development via acting directly in chondrocytes and osteoblasts. In this study, we focused on TH effects on the secondary ossification center (SOC) because the time of appearance of SOCs in several species coincides with the time when peak levels of TH are attained. Accordingly, micro–computed tomography (µCT) evaluation of femurs and tibias at day 21 in TH‐deficient and control mice revealed that endochondral ossification of SOCs is severely compromised owing to TH deficiency and that TH treatment for 10 days completely rescued this phenotype. Staining of cartilage and bone in the epiphysis revealed that whereas all of the cartilage is converted into bone in the prepubertal control mice, this conversion failed to occur in the TH‐deficient mice. Immunohistochemistry studies revealed that TH treatment of thyroid stimulating hormone receptor mutant (Tshr^?/?) mice induced expression of Indian hedgehog (Ihh) and Osx in type 2 collagen (Col2)‐expressing chondrocytes in the SOC at day 7, which subsequently differentiate into type 10 collagen (Col10)/osteocalcin‐expressing chondro/osteoblasts at day 10. Consistent with these data, treatment of tibia cultures from 3‐day‐old mice with 10 ng/mL TH increased expression of Osx, Col10, alkaline phosphatase (ALP), and osteocalcin in the epiphysis by sixfold to 60‐fold. Furthermore, knockdown of the TH‐induced increase in Osx expression using lentiviral small hairpin RNA (shRNA) significantly blocked TH‐induced ALP and osteocalcin expression in chondrocytes. Treatment of chondrogenic cells with an Ihh inhibitor abolished chondro/osteoblast differentiation and SOC formation. Our findings indicate that TH regulates the SOC initiation and progression via differentiating chondrocytes into bone matrix–producing osteoblasts by stimulating Ihh and Osx expression in chondrocytes. © 2014 American Society for Bone and Mineral Research.     

Immunolocalization of vascular endothelial growth factor during heterotopic bone formation induced from grafted periosteum

Vessel invasion is an important step in cartilage replacement that leads to bone formation, and vascular endothelial growth factor (VEGF) has been implicated as a key player in this process. Although grafted periosteum undergoes endochondral ossification, little is known about the role of VEGF in this process. In the current study the authors investigated by immunohistochemical, histochemical, and ultrastructural techniques the localization of VEGF during bone formation in periosteal grafts. At day 14 after grafting the tibias of Japanese white rabbits, periosteal cells in the grafted tissue had differentiated into chondrocytes to form cartilage. Some chondrocytes were immunopositive for VEGF expression, and subsequent vessel invasion occurred predominantly in these VEGF-positive areas. At day 45, the cartilage invaded by blood vessels had been replaced by newly formed bone. These findings suggest that VEGF is associated with the process of blood vessel invasion into cartilage before bone replacement in endochondral ossification from grafted periosteum.