Oral and Craniofacial Development Overview PDF

Oral and Craniofacial development Overview Dr. Ana Angelova Volponi The development of a complex organism from a single cell, the fertilised egg, has fascinated people for centuries How is it that all tissues and organs form in the right places and at the right time? How is the development of differ...

Oral and Craniofacial development Overview Dr. Ana Angelova Volponi The development of a complex organism from a single cell, the fertilised egg, has fascinated people for centuries How is it that all tissues and organs form in the right places and at the right time? How is the development of different organ systems coordinated, so that they all fit together correctly at the end? Embryo development is highly reproducible and exquisitely regulated. Development-Process of progressive change of organism Ageing- Process of getting older Fertilized egg (zygote) newborn Embryonic development adult Postnatal development regeneration /repair aging Embryology Developmental biology Ageing Questions of Developmental biology Cell differentiation Zygote hundreds of different cell types Morphogenesis (acquisition of organised form) Zygote distinct tissues and organs Growth control and coordination of cell division Reproduction egg+sperm zygote multicellular organism (egg+sperm) Evolution changes in development Environmental integration example: sex determination in crocs new body forms temperatures experienced during embryonic development determine the sex of the offspring Approaches in developmental biology Anatomical Experimental Genetic Anatomical approaches Descriptive and comparative embryology Epigenesis vs Preformation Epigenesis= organs form “de novo” Preformation= embryo is a miniature version of the adult Today: Instruction for development “preformed” Hartsoeker’s “Homunculus” …The epigenesis of something preformed… Aim of descriptive/comparative embryology understand “normal development” Normal development= course of development for a typical embryo, free of disturbances Haeckel’s Embryos between 1868 and 1908 very early somewhat later still later “Ontogeny recapitulates phylogeny” – our embryonic development repeats our e volutionary past. This aphorism was soon disproved, but the use of Haeckel’s drawings persisted 1997, became popular again by Creationists Chicken as a biological research model What makes the chick embryo “an attractive model system” ?! -classic ‘cut and paste’ experiments and mechanistic gene function -analyses. -combination of micromanipulations with gain- or loss-of-function is particularly powerful. -recent development of advanced imaging techniques make major contributions to our understanding of molecular and cellular mechanisms controlling developmental processes. The chick embryo is: Easy to access and observe In the early stages, chick embryo morphology is very similar to human, both are amniotes and their development is very similar. The chicken and human genomes share considerable homology. We can use chick embryos to visualise complex processes, including cell migration, cell– cell communication, cell differentiation and tissue morphogenesis, in an amniote system. The molecular and cellular basis for many developmental processes and phenomena were first described in the chick, including limb patterning, neural crest migration, dorso-ventral neural tube patterning, blood vessel formation, somite segmentation and left– right asymmetry. Experiments in chicken, which examine the function of genes, have helped elucidate the underlying mechanisms of human genetic diseases and provide a basis for testing novel therapies. Time-lapse video microscopy can be used to image live chick embryos, either in ovo or ex ovo using embryo culture. 14 Zebrafish make excellent research model ! As zebrafish eggs are fertilised and develop outside the mother's body it is an ideal model organism for studying early development. Zebrafish have a similar genetic structure to humans. They share 70 per cent of genes with us. 84 % of genes known to be associated with human disease have a zebrafish counterpart. Five reasons why Zebrafish make excellent research models 1. Genetic similarity to humans Zebrafish are vertebrates and therefore share a high degree of sequence and functional homology with mammals, including humans. 2. Easier to house and care for than rodents 3. Impact of any genetic mutation or drug treatment is easy to see Zebrafish embryos and larvae are completely transparent, meaning that it is possible to follow the impact of a genetic manipulation or pharmacological treatment using non-invasive imaging techniques. 4. Lots of offspring 5. Easier to introduce genetic changes Zebrafish embryos are able to absorb chemicals that have been added to their water, meaning it is easy to introduce changes to their genes using nothing more than chemical mutagens. Zebrafish are able to withstand much higher levels of chemical mutagens than can be tolerated by rodents so it is possible to induce a much higher density of mutations in their genome. 18 MAKING FACES Frontonasal process Nasal proces ses (M)-medial (L)-lateral Maxillary process Stomatodeum Pericardial buldging Mandibulary process Who/What directs the growth and development of our faces? What are the tools and commands? Neural Crest cells Embryonic days 8.0 to 9.5 CARTILAGE chondroblasts, chondrocytes Head BONE osteoblasts, ostecytes CRANIAL TEETH odontoblasts, cementoblasts MELANOCYTES TRUNK TRUNK Tail NEURONS (sensory, sympathetic) Adrenomedullary cells Schwann cells Replacing teeth Sharks can loose one tooth in a week Lost teeth can be replaced in a day! 29 What about the human teeth? Dyphodont Heterodont Thecodont Cleidocranial dysplasia (Runx2 +/-): Supernumerary teeth forming as a third dentition Continuous tooth formation unlocked ? bone hypoplasia Runx2 inhibits the formation of successional teeth Ectodermal Dysplasia Over 150 ectodermal dysplasia syndromes – 1:1500 births Most common = Hypohidrotic ED – Sparse hair – Abnormal dentition – Absence of sweat glands (Munoz 1997) – Tear ducts, salivary glands, etc – Characteristic facial features Can be X-linked, autosomal recessive or dominant (Belshi 2002) Genes causing dental defects in man Condition Associated defects Gene Type of molecule Oligodontia None PAX9 FGF signal target Oligodontia None , cleft palate MSX1 BMP signal target Oligodontia Colorectal cancer AXIN2 WNT signal modulator Ectodermal dysplasia Hypoplastic hair / EDA TNF signal (ectodysplasin) glands EDAR TNF receptor (hypohidrotic, HED) EDARADD TNF signal mediator EEC Ectodermal dysplasia, P63 FGF and BMP target PITX2 FGF signal target RUNX2 FGF signal mediator ectrodactyly, cleft palate Rieger syndrome Eye defects Cleidocranial dysplasia bone hypoplasia “Disturbed” Dental Development …pre-natal …post-natal What do you see? Billiary atresia Ectodermal dysplasia Disturbances in number Disturbances in size Disturbances in shape of teeth Disturbances in structure Summary It is fascinating! How a complex organism (like you!) can develop from a single cell, the fertilised egg, Embryo development is highly reproducible and exquisitely regulated. All tissues and organs form in the right places and at the right time? Using animal experimental models , which examine the function of genes, we can understand the underlying mechanisms of human genetic diseases and provide a basis for testing novel therapies. Anatomy and Histology of dental tissues Anatomy/histo logy Function/physiology/p athology Clinical relevance Enamel amelogenesis dentinogenesisis Dentin Dental Pulp Cementum Periodontal Ligament Gingiva Alveolar Bone DentinPulp Complex Periodont ium Clinical Relevance Infants and young children deciduous& mixed dentitions -Immature and weaker enamel crystal structure -Underdeveloped salivary glands -Necessity for increased frequency of food intake, leading to extended demineralization time Adolescents and high teens -Beginning of life style disorders -Irregular dietary habits -Lack of oral hygene -Irregular visits to dental clinics Demineralisation risk The elderly Adults -Mature tooth enamel (critical pH 5.5-5.7) Adults: females during pregnancy -Salivary pH lower -Changes in endocrine function – increased risk of gum disease -Life style disorders (adverse changes to diet and oral hygene practices) -Reduced salivary flow due to medication, systematic diseases and ageing -Root surfaces exposed -Reduced masticatory forces -Changing dietand ingestion of soft food Periodontal changes Summary The Oral and Craniofacial Biology course encompasses the disciplines of craniofacial biology and development, craniofacial anatomy, histology, and physiology, molecular biology and genetics, microbiology and immunology. Because of the unique combination of tissue types and functions of the mouth and craniofacial complex, the field of oral biology blends fundamental scientific disciplines in unique and fascinating way, setting the basic science background to clinical practice in dentistry. Development and ageing, as programmed factors and other external damage-related factors influence the changes on cell, tissue, organ level. Teeth and supporting structures are dynamic systems that undergo CONSTANT changes KEATS resources Anatomy of Head and Neck Embryology and development Examined in Format ive 2 and Summativ e2 Tooth and supporting tissues Oral Biology KEATS resources Padlet walls Ask questions anonymously Use for revision !!