Molecular regulatory mechanism of tooth root development

The root is crucial for the physiological function of the tooth, and a healthy root allows an artificial crown to function as required clinically. Tooth crown development has been studied intensively during the last few decades, but root development remains not well understood. Here we review the root development processes, including cell fate determination, induction of odontoblast and cementoblast differentiation, interaction of root epithelium and mesenchyme, and other molecular mechanisms. This review summarizes our current understanding of the signaling cascades and mechanisms involved in root development. It also sets the stage for de novo tooth regeneration.

3D printing of hydroxyapatite/tricalcium phosphate scaffold with hierarchical porous structure for bone regeneration

Three-dimensional(3D)-printed scaffolds have attracted considerable attention in recent years as they provide a suitable environment for bone cell tissue regeneration and can be customized in shape.Among many other challenges,the material composition and geometric structure have major impacts on the performance of scaffolds.Hydroxyapatite and tricalcium phosphate(HA/TCP),as the major constituents of natural bone and teeth,possess attractive biological properties and are widely used in bone scaffold fabrication.Many fabrication methods have been investigated in attempts to achieve HA/TCP scaffolds with microporous structure enabling cell growth and nutrient transport.However,current 3D printing methods can only achieve the fabrication of HA/TCP scaffolds with certain range of microporous structure.To overcome this challenge,we developed a slurry-based microscale mask image projection stereolithography,allowing us to form a HA/TCP-based photocurable suspension with complex geometry including biomimetic features and hierarchical porosity.Here,the curing performance and physical properties of the HA/TCP suspension were investigated,and a circular movement process for the fabrication of highly viscous HA/TCP suspension was developed.Based on these investigations,the scaffold composition was optimized.We determined that a 30 wt%HA/TCP scaffold with biomimetic hierarchical structure exhibited superior mechanical properties and porosity.Cell proliferation was investigated in vitro,and the surgery was conducted in a nude mouse in vivo model of long bone with cranial neural crest cells and bone marrow mesenchymal stem cells.The results showed our 3D-printed HA/TCP scaffold with biomimetic hierarchical structure is biocompatible and has sufficient mechanical strength for surgery.

以转化为导向的口腔医学与干细胞研究

上个世纪末以来,突飞猛进的干细胞研究成为促进人类医学乃至生命科学发展的生力军。在口腔医学领域,相关成体干细胞的研究不仅扩展了我们对口腔组织器官发育、维持生理活动的认识水平,而且在口腔疾病发生、发展机制与治疗策略方面更是产生了突破性的进展。

同源盒基因Msx2在小鼠磨牙牙根发育早期的表达

目的:观察在小鼠的牙根发育早期同源盒基因Msx2的表达,以探讨其在此过程中所起的作用。方法:出生后第6天和第8天的小鼠,取含有下颌第一磨牙的下颌骨,进行固定和脱钙,制备5μm的石蜡切片,原位杂交方法检测Msx2在小鼠牙根发育早期的表达。结果:第6天Msx2阳性信号出现在Hertwig’s上皮根鞘细胞、上皮根鞘周围的牙乳头细胞和早期的成牙本质细胞中;第8天在Hertwig’s上皮根鞘细胞、上皮根鞘周围的牙乳头细胞和成牙本质细胞中Msx2有阳性信号,而在成牙骨质细胞中无表达。结论:Msx2参与调控牙根早期发育的生理过程。

BMP-IHH-mediated interplay between mesenchymal stem cells and osteoclasts supports calvarial bone homeostasis and repair

Calvarial bones are connected by fibrous sutures. These sutures provide a niche environment that includes mesenchymal stem cells(MSCs), osteoblasts, and osteoclasts, which help maintain calvarial bone homeostasis and repair. Abnormal function of osteogenic cells or diminished MSCs within the cranial suture can lead to skull defects, such as craniosynostosis. Despite the important function of each of these cell types within the cranial suture, we have limited knowledge about the role that crosstalk between them may play in regulating calvarial bone homeostasis and injury repair. Here we show that suture MSCs give rise to osteoprogenitors that show active bone morphogenetic protein(BMP) signalling and depend on BMP-mediated Indian hedgehog(IHH) signalling to balance osteogenesis and osteoclastogenesis activity. IHH signalling and receptor activator of nuclear factor kappa-Β ligand(RANKL) may function synergistically to promote the differentiation and resorption activity of osteoclasts. Loss of Bmpr1a in MSCs leads to downregulation of hedgehog(Hh) signalling and diminished cranial sutures. Significantly, activation of Hh signalling partially restores suture morphology in Bmpr1a mutant mice, suggesting the functional importance of BMP-mediated Hh signalling in regulating suture tissue homeostasis. Furthermore, there is an increased number of CD200+ cells in Bmpr1a mutant mice, which may also contribute to the inhibited osteoclast activity in the sutures of mutant mice. Finally, suture MSCs require BMPmediated Hh signalling during the repair of calvarial bone defects after injury. Collectively, our studies reveal the molecular and cellular mechanisms governing cell–cell interactions within the cranial suture that regulate calvarial bone homeostasis and repair.

Cementomimetics——constructing a cementum-like biomineralized microlayer via amelogenin-derived peptides

Cementum is the outer-, mineralized-tissue covering the tooth root and an essential part of the system of periodontal tissue that anchors the tooth to the bone. Periodontal disease results from the destructive behavior of the host elicited by an infectious biofilm adhering to the tooth root and left untreated, may lead to tooth loss. We describe a novel protocol for identifying peptide sequences from native proteins with the potential to repair damaged dental tissues by controlling hydroxyapatite biomineralization. Using amelogenin as a case study and a bioinformatics scoring matrix, we identified regions within amelogenin that are shared with a set of hydroxyapatite-binding peptides （HABPs） previously selected by phage display. One 22-amino acid long peptide regions referred to as amelogenin-derived peptide 5 （ADP5） was shown to facilitate cell-free formation of a cementum-like hydroxyapatite mineral layer on demineralized human root dentin that, in turn, supported attachment of periodontal ligament cells in vitro. Our findings have several implications in peptide-assisted mineral formation that mimic biomineralization. By further elaborating the mechanism for protein control over the biomineral formed, we afford new insights into the evolution of protein-mineral interactions. By exploiting small peptide domains of native proteins, our understanding of structure-function relationships of biomineralizing proteins can be extended and these peptides can be utilized to engineer mineral formation. Finally, the cementomimetic layer formed by ADP5 has the potential clinical application to repair diseased root surfaces so as to promote the regeneration of periodontal tissues and thereby reduce the morbiditv associated with tooth loss.

Meeting report:a hard look at the state of enamel research

The Encouraging Novel Amelogenesis Models and Ex vivo cell Lines （ENAMEL） Development workshop was held on 23 June 2017 at the Bethesda headquarters of the National institute of Dental and Craniofacial Research （NIDCR）. Discussion topics included model organisms, stem cells/cell lines, and tissues/3D cell culture/organoids. Scientists from a number of disciplines, representing institutions from across the United States, gathered to discuss advances in our understanding of enamel, as well as future directions for the field.

腭裂分子发病机制的新进展(英文)

Cleft palate represents one of the major groups of congenital birth defects in the human population.Despite recent advancements in medical intervention,babies born with cleft palate often suffer multiple handicaps that signifi-cantly compromise the quality of their lives.Investigations of craniofacial development and malformations

绿茶提取物对人乳头瘤病毒16癌蛋白诱导的人宫颈癌细胞缺氧诱导因子1α和血管内皮生长因子表达的影响

目的研究绿茶提取物（GTE）及其主要成分表没食子儿茶素没食子酸酯（EGCG）干预对人乳头瘤病毒16（HPV-16）癌蛋白（E6和E7）诱导的人宫颈癌C-33A细胞缺氧诱导因子1α（HIF-1α）和血管内皮生长因子（VEGF）表达的影响。方法将宫颈癌细胞分为瞬时转染空质粒HA-pSG5（空质粒组）、HA-pSG5-HPV-16E6质粒（16E6组）、16E7质粒（16E7组）和模拟转染组，转染后18、24和48h以蛋白质印迹法检测各组细胞HIF-1α蛋白的表达，酶联免疫吸附试验检测VEGF蛋白的表达。转染后24h，分别用不同浓度GTE或EGCG处理16E6、16E7组细胞不同时间，并设未用GTE或EGCG处理组（未干预组），同法检测各组细胞HIF-10α和VEGF蛋白的表达，实时PCR检测HIF-1α和VEGF mRNA的表达。结果转染后24h，16E6和16E7组细胞HIF-10L蛋白表达明显增加；VEGF蛋白分别为（870166）、（1487±51）pg／ml，均明显高于空质粒组[（366±65）pg／ml，均P〈0．01]。40μg/ml GTE或50μmol／L EGCG处理16h即可明显抑制16E6、16E7组细胞HIF-1α蛋白表达；16E6组VEGF蛋白分别为（476±34）、（477±65）pg／ml，VEGF mRNA分别为1．208±0．196、1．174±0．208，均明显低于未干预组[分别为（870±66）pg／ml、1．805±0．081，均P〈0．01）；16E7组VEGF蛋白分别为（649±55）、（514±37）pg／ml，VEGF mRNA分别为1．442±0．136、1．399±0．064，均明显低于未干预组[分别为（1487±51）pg／ml、2．123±0．120，均P〈0．01）。80μg／mlGTE或100μmol／I。EGCG对VEGF蛋白表达的抑制作用明显强于40μg／ml GTE或50μmol／LEGCG（均P〈0．01）。结论GTE和EGCG对HPV-16癌蛋白诱导的人宫颈癌细胞HIF-1α蛋白、VEGF蛋白及mRNA表达具有明硅抑制作用，其中对VEGF蛋白表达的抑制作用呈明显的剂量依赖性。