How osteoblast cells are induced is a central question for understanding skeletal formation. Abnormal osteoblast differentiation leads to a broad range of devastating craniofacial diseases. Here we have investigated i...How osteoblast cells are induced is a central question for understanding skeletal formation. Abnormal osteoblast differentiation leads to a broad range of devastating craniofacial diseases. Here we have investigated intramembranous ossification during cranial bone development in mouse models of skeletal genetic diseases that exhibit craniofacial bone defects. The GNAS gene encodes Gαs that transduces GPCR signaling. GNAS activation or loss-of-function mutations in humans cause fibrous dysplasia(FD) or progressive osseous heteroplasia(POH) that shows craniofacial hyperostosis or craniosynostosis, respectively. We find here that, while Hh ligand-dependent Hh signaling is essential for endochondral ossification, it is dispensable for intramembranous ossification, where Gαsregulates Hh signaling in a ligand-independent manner. We further show that Gαscontrols intramembranous ossification by regulating both Hh and Wnt/β-catenin signaling. In addition, Gαsactivation in the developing cranial bone leads to reduced ossification but increased cartilage presence due to reduced cartilage dissolution, not cell fate switch. Small molecule inhibitors of Hh and Wnt signaling can effectively ameliorate cranial bone phenotypes in mice caused by loss or gain of Gnas function mutations, respectively. Our work shows that studies of genetic diseases provide invaluable insights in both pathological bone defects and normal bone development, understanding both leads to better diagnosis and therapeutic treatment of bone diseases.展开更多
Mandibular defects caused by injuries,tumors,and infections are common and can severely affect mandibular function and the patient's appearance.However,mandible reconstruction with a mandibular bionic structure re...Mandibular defects caused by injuries,tumors,and infections are common and can severely affect mandibular function and the patient's appearance.However,mandible reconstruction with a mandibular bionic structure remains challenging.Inspired by the process of intramembranous ossification in mandibular development,a hierarchical vascularized engineered bone consisting of angiogenesis and osteogenesis modules has been produced.Moreover,the hierarchical vascular network and bone structure generated by these hierarchical vascularized engineered bone modules match the particular anatomical structure of the mandible.The ultra-tough polyion complex has been used as the basic scaffold for hierarchical vascularized engineered bone for ensuring better reconstruction of mandible function.According to the results of in vivo experiments,the bone regenerated using hierarchical vascularized engineered bone is similar to the natural mandibular bone in terms of morphology and genomics.The sonic hedgehog signaling pathway is specifically activated in hierarchical vascularized engineered bone,indicating that the new bone in hierarchical vascularized engineered bone underwent a process of intramembranous ossification identical to that of mandible development.Thus,hierarchical vascularized engineered bone has a high potential for clinical application in mandibular defect reconstruction.Moreover,the concept based on developmental processes and bionic structures provides an effective strategy for tissue regeneration.展开更多
γ-Secretase,called“the proteasome of the membrane,”is a membrane-embedded protease complex that cleaves 150+peptide substrates with central roles in biology and medicine,including amyloid precursor protein and the ...γ-Secretase,called“the proteasome of the membrane,”is a membrane-embedded protease complex that cleaves 150+peptide substrates with central roles in biology and medicine,including amyloid precursor protein and the Notch family of cell-surface receptors.Mutations inγ-secretase and amyloid precursor protein lead to early-onset familial Alzheimer’s disease.γ-Secretase has thus served as a critical drug target for treating familial Alzheimer’s disease and the more common late-onset Alzheimer’s disease as well.However,critical gaps remain in understanding the mechanisms of processive proteolysis of substrates,the effects of familial Alzheimer’s disease mutations,and allosteric modulation of substrate cleavage byγ-secretase.In this review,we focus on recent studies of structural dynamic mechanisms ofγ-secretase.Different mechanisms,including the“Fit-Stay-Trim,”“Sliding-Unwinding,”and“Tilting-Unwinding,”have been proposed for substrate proteolysis of amyloid precursor protein byγ-secretase based on all-atom molecular dynamics simulations.While an incorrect registry of the Notch1 substrate was identified in the cryo-electron microscopy structure of Notch1-boundγ-secretase,molecular dynamics simulations on a resolved model of Notch1-boundγ-secretase that was reconstructed using the amyloid precursor protein-boundγ-secretase as a template successfully capturedγ-secretase activation for proper cleavages of both wildtype and mutant Notch,being consistent with biochemical experimental findings.The approach could be potentially applied to decipher the processing mechanisms of various substrates byγ-secretase.In addition,controversy over the effects of familial Alzheimer’s disease mutations,particularly the issue of whether they stabilize or destabilizeγ-secretase-substrate complexes,is discussed.Finally,an outlook is provided for future studies ofγ-secretase,including pathways of substrate binding and product release,effects of modulators on familial Alzheimer’s disease mutations of theγ-secretase-substrate complexes.Comprehensive understanding of the functional mechanisms ofγ-secretase will greatly facilitate the rational design of effective drug molecules for treating familial Alzheimer’s disease and perhaps Alzheimer’s disease in general.展开更多
To evaluate the characteristics and synthesis activity of osteoblasts extracted from the calvaria of offspring of rats exposed to maternal hyperthyroidism.Twelve adult Wistar rats were divided into two groups,one cont...To evaluate the characteristics and synthesis activity of osteoblasts extracted from the calvaria of offspring of rats exposed to maternal hyperthyroidism.Twelve adult Wistar rats were divided into two groups,one control and one treated with daily administration of L-thyroxine by an orogastric tube(50μg/animal/day)during pregnancy.Three days after delivery and confirmation of the mothers’hyperthyroidism,the offspring were euthanized for the extraction of osteoblasts from the calvaria.At 7,14,and 21 days,proliferation activity was assessed using MTT assay,while alkaline phosphatase(ALP)activity was assessed by the BCIP/NBT method.At 21 days,the total area of the mineralized matrix stained by von Kossa was evaluated by morphometry.The expression of gene transcripts for Runx2,Bmp2,Fgfr1,collagen type 1(Col1),osteocalcin(Oc),and osteopontin(Op)were evaluated by real-time RT-PCR.Means were compared using the Student’s t-test.FA activity was significantly higher at 14 and 21 days in cultures of osteoblasts extracted from offspring exposed to maternal hyperthyroidism,while MTT conversion was significantly lower at 21 days in this group.Osteoblast cultures of neonates exposed to maternal hyperthyroidism also showed a larger total area of mineralized matrix and greater expression of gene transcripts for Oc and Op.Maternal hyperthyroidism increases the activity of matrix synthesis,alkaline phosphatase activity,and expression of gene transcripts for osteocalcin and osteopontin in the osteoblasts,extracted from the calvaria of the offspring,which may be one of the mechanisms of premature fusion of cranial sutures.展开更多
目的 建立兔下颌骨牵拉成骨动物模型,研究了解颅面部牵拉骨生成的规律。方法 将12 只新西兰大白兔右侧下颌骨第一磨牙前完全截骨后用牵拉器固定,左侧不做手术为对照侧。1周后以每天一次0.9 m m 的速度逐步牵拉,连续10 天。牵拉完成后1...目的 建立兔下颌骨牵拉成骨动物模型,研究了解颅面部牵拉骨生成的规律。方法 将12 只新西兰大白兔右侧下颌骨第一磨牙前完全截骨后用牵拉器固定,左侧不做手术为对照侧。1周后以每天一次0.9 m m 的速度逐步牵拉,连续10 天。牵拉完成后1 天,2、4 和8 周每组处死3只兔,取下完整下颌骨进行大体测量,X线摄片,新骨组织学观察。结果 12只兔右侧下颌骨平均延长8.3 m m ,与对照侧比较有显著性差异(P< 0.01),无骨不连及畸形愈合。X线摄片发现,延长完成后2周牵拉间隙已被骨痂桥接,8 周时,X线片上很难分辨新骨和正常骨。组织学观察牵拉早期即有胶原束形成,随后钙化成骨,未发现软骨中介体。结论 运用牵拉成骨技术可成功地延长兔下颌骨,无骨不连和畸形愈合等并发症。展开更多
基金supported by the NIH grants R01DE025866 from NIDCRR01AR070877 from NIAMSsupported by the 111 Project, MOE (B14038), China
文摘How osteoblast cells are induced is a central question for understanding skeletal formation. Abnormal osteoblast differentiation leads to a broad range of devastating craniofacial diseases. Here we have investigated intramembranous ossification during cranial bone development in mouse models of skeletal genetic diseases that exhibit craniofacial bone defects. The GNAS gene encodes Gαs that transduces GPCR signaling. GNAS activation or loss-of-function mutations in humans cause fibrous dysplasia(FD) or progressive osseous heteroplasia(POH) that shows craniofacial hyperostosis or craniosynostosis, respectively. We find here that, while Hh ligand-dependent Hh signaling is essential for endochondral ossification, it is dispensable for intramembranous ossification, where Gαsregulates Hh signaling in a ligand-independent manner. We further show that Gαscontrols intramembranous ossification by regulating both Hh and Wnt/β-catenin signaling. In addition, Gαsactivation in the developing cranial bone leads to reduced ossification but increased cartilage presence due to reduced cartilage dissolution, not cell fate switch. Small molecule inhibitors of Hh and Wnt signaling can effectively ameliorate cranial bone phenotypes in mice caused by loss or gain of Gnas function mutations, respectively. Our work shows that studies of genetic diseases provide invaluable insights in both pathological bone defects and normal bone development, understanding both leads to better diagnosis and therapeutic treatment of bone diseases.
基金National Key Research and Development Program of China(2018YFA0703000)National Natural Science Foundation of China(8212200044,52075482,82071085,81873720)+2 种基金Zhejiang Provincial Natural Science Foundation of China(LR21H140001)Key Research and Development Program of Zhejiang,China(2017C01054,2018C03062)Scientific Research Fund of Zhejiang Provincial Education Department(Y202045564)。
文摘Mandibular defects caused by injuries,tumors,and infections are common and can severely affect mandibular function and the patient's appearance.However,mandible reconstruction with a mandibular bionic structure remains challenging.Inspired by the process of intramembranous ossification in mandibular development,a hierarchical vascularized engineered bone consisting of angiogenesis and osteogenesis modules has been produced.Moreover,the hierarchical vascular network and bone structure generated by these hierarchical vascularized engineered bone modules match the particular anatomical structure of the mandible.The ultra-tough polyion complex has been used as the basic scaffold for hierarchical vascularized engineered bone for ensuring better reconstruction of mandible function.According to the results of in vivo experiments,the bone regenerated using hierarchical vascularized engineered bone is similar to the natural mandibular bone in terms of morphology and genomics.The sonic hedgehog signaling pathway is specifically activated in hierarchical vascularized engineered bone,indicating that the new bone in hierarchical vascularized engineered bone underwent a process of intramembranous ossification identical to that of mandible development.Thus,hierarchical vascularized engineered bone has a high potential for clinical application in mandibular defect reconstruction.Moreover,the concept based on developmental processes and bionic structures provides an effective strategy for tissue regeneration.
基金supported in part by Award 2121063 from National Science Foundation(to YM)AG66986 from the National Institutes of Health(to MSW).
文摘γ-Secretase,called“the proteasome of the membrane,”is a membrane-embedded protease complex that cleaves 150+peptide substrates with central roles in biology and medicine,including amyloid precursor protein and the Notch family of cell-surface receptors.Mutations inγ-secretase and amyloid precursor protein lead to early-onset familial Alzheimer’s disease.γ-Secretase has thus served as a critical drug target for treating familial Alzheimer’s disease and the more common late-onset Alzheimer’s disease as well.However,critical gaps remain in understanding the mechanisms of processive proteolysis of substrates,the effects of familial Alzheimer’s disease mutations,and allosteric modulation of substrate cleavage byγ-secretase.In this review,we focus on recent studies of structural dynamic mechanisms ofγ-secretase.Different mechanisms,including the“Fit-Stay-Trim,”“Sliding-Unwinding,”and“Tilting-Unwinding,”have been proposed for substrate proteolysis of amyloid precursor protein byγ-secretase based on all-atom molecular dynamics simulations.While an incorrect registry of the Notch1 substrate was identified in the cryo-electron microscopy structure of Notch1-boundγ-secretase,molecular dynamics simulations on a resolved model of Notch1-boundγ-secretase that was reconstructed using the amyloid precursor protein-boundγ-secretase as a template successfully capturedγ-secretase activation for proper cleavages of both wildtype and mutant Notch,being consistent with biochemical experimental findings.The approach could be potentially applied to decipher the processing mechanisms of various substrates byγ-secretase.In addition,controversy over the effects of familial Alzheimer’s disease mutations,particularly the issue of whether they stabilize or destabilizeγ-secretase-substrate complexes,is discussed.Finally,an outlook is provided for future studies ofγ-secretase,including pathways of substrate binding and product release,effects of modulators on familial Alzheimer’s disease mutations of theγ-secretase-substrate complexes.Comprehensive understanding of the functional mechanisms ofγ-secretase will greatly facilitate the rational design of effective drug molecules for treating familial Alzheimer’s disease and perhaps Alzheimer’s disease in general.
基金supported by grants from the Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)Fundação de Amparo a Pesquisa de Minas Gerais(Fapemig)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior(Capes).
文摘To evaluate the characteristics and synthesis activity of osteoblasts extracted from the calvaria of offspring of rats exposed to maternal hyperthyroidism.Twelve adult Wistar rats were divided into two groups,one control and one treated with daily administration of L-thyroxine by an orogastric tube(50μg/animal/day)during pregnancy.Three days after delivery and confirmation of the mothers’hyperthyroidism,the offspring were euthanized for the extraction of osteoblasts from the calvaria.At 7,14,and 21 days,proliferation activity was assessed using MTT assay,while alkaline phosphatase(ALP)activity was assessed by the BCIP/NBT method.At 21 days,the total area of the mineralized matrix stained by von Kossa was evaluated by morphometry.The expression of gene transcripts for Runx2,Bmp2,Fgfr1,collagen type 1(Col1),osteocalcin(Oc),and osteopontin(Op)were evaluated by real-time RT-PCR.Means were compared using the Student’s t-test.FA activity was significantly higher at 14 and 21 days in cultures of osteoblasts extracted from offspring exposed to maternal hyperthyroidism,while MTT conversion was significantly lower at 21 days in this group.Osteoblast cultures of neonates exposed to maternal hyperthyroidism also showed a larger total area of mineralized matrix and greater expression of gene transcripts for Oc and Op.Maternal hyperthyroidism increases the activity of matrix synthesis,alkaline phosphatase activity,and expression of gene transcripts for osteocalcin and osteopontin in the osteoblasts,extracted from the calvaria of the offspring,which may be one of the mechanisms of premature fusion of cranial sutures.
文摘目的 建立兔下颌骨牵拉成骨动物模型,研究了解颅面部牵拉骨生成的规律。方法 将12 只新西兰大白兔右侧下颌骨第一磨牙前完全截骨后用牵拉器固定,左侧不做手术为对照侧。1周后以每天一次0.9 m m 的速度逐步牵拉,连续10 天。牵拉完成后1 天,2、4 和8 周每组处死3只兔,取下完整下颌骨进行大体测量,X线摄片,新骨组织学观察。结果 12只兔右侧下颌骨平均延长8.3 m m ,与对照侧比较有显著性差异(P< 0.01),无骨不连及畸形愈合。X线摄片发现,延长完成后2周牵拉间隙已被骨痂桥接,8 周时,X线片上很难分辨新骨和正常骨。组织学观察牵拉早期即有胶原束形成,随后钙化成骨,未发现软骨中介体。结论 运用牵拉成骨技术可成功地延长兔下颌骨,无骨不连和畸形愈合等并发症。
