Oral Cavity, Saliva & Extracellular Matrix (Lesson 11 PDF)

ORAL CAVITY • The Saliva • Extracellular Matrix of Periodontum THE SALIVA: Composition and Function THE SALIVA Saliva is the secretion of the salivary glands which ensures stability in the oral cavity environment. The salivary glands are innervated via the autonomic nervous system.  MAJOR SALI...

ORAL CAVITY • The Saliva • Extracellular Matrix of Periodontum THE SALIVA: Composition and Function THE SALIVA Saliva is the secretion of the salivary glands which ensures stability in the oral cavity environment. The salivary glands are innervated via the autonomic nervous system.  MAJOR SALIVARY GLANDS (responsible of 90% of saliva production) • Parotid gland - Saliva little viscous, rich in alpha-amylase and phosphate • Submaxilar and Sublingual glands – Saliva little viscous, rich in calcium iones and glycoproteins MINOR SALIVARY GLANDS • Accesory glands – Responsible of 10% of saliva production – Saliva rich in cloride 3. 1. 2. 1. Parotid 2. Submaxilar 3. Sublingual SECRETION OF SALIVA or SALIVAL FLOW In humans • The Salival Flow (SF) has large biological variation: – 0,5-1 L per day – Medium volumen in the oral cavity: 1 mL – Swallowing reflects: (renovation 500-1000 times/day) • The secretion velocity is: – 0,3 mL / minute, unstimulated – 5 mL / minute, stimulated • The secretion can be inhibited by : - Dream, fear, stres, anesthesia, drugs Alterations of Salival Flow (SF): - Xerostomia, hiposalivation, hyposialia: it is define as a diminution of salival flow less than a half of unstimulated SF. - Hypersalivation, hipersialia, ptyialism: increasing of salival flow. SALIVA COMPOSITION and FUNCTION The major component of saliva is WATER. Salivary fluid is an exocrine secretion composed of water (99%) and the remaining 1% composed of other substances: INORGANIC SUBSTANCES Na, K, Ca, Mg, HYDROGEN CARBONATES, PHOSPHATES, FLUORIDE, SULFATE AND IODIDE. ORGANIC SUBSTANCES PROTEINS, CARBOHYDRATES, UREA, AMMONIUM, CHOLESTEROL, LACTATE AND CITRATE PROTECTION ROLE OF SALIVA • Mechanical protection –Lubricant for hard-textured food –Viscoelastic properties (glycoproteins) • Chemical protection – Regulating the pH of saliva - Control of enamel solubility - Enamel remineralization • Antimicrobial protection – Antiseptical and Immune properties: Lysozyme, IgA, IgM, Proline rich proteins, lactoferrins, peroxidases. –Washing and removal of bacteria and toxins –Inhibition of xerostomia Regulating pH in the oral cavity • Oral acidity origin –From food –Fermentation process (from bacteria) • The acidity stimulates the secretion of saliva • pH normal range: 6-6.5 – [CO3H‒] = 1.3 mM – [PO4H2‒] = 5 mM • Saliva stimulated by acid: pH: 7.5-8 – [CO3H‒] = 30-60 mM – [PO4H2‒] = 2 mM – The saliva regulates the acidity: * Dilution of acids * Buffering capacity (proteins, carbonate and phosphate) SYSTEMS TO Maintain the pH Buffer bicarbonate pKa = 6,1 Buffer phosphate pKa = 6,86 Some proteins ( ej. Histatins and sialine) Ammonium produces by bacteria Saliva is used as a tool for the diagnosis of both oral and systemic diseases • Salivary fluid contains not only the saliva itself, but contains crevicular fluid, mucosal transudates, bacteria, food debris and cells. • Chemical substances that are not among its normal components can reach the saliva using the following pathways: - intracellular pathways: passive difussion and active transport. - extracellular pathways (serum-saliva) * Ultrafiltration through the tight cell junctions * by passing through the capillary barrier * the interstitial spaces * the membranes of the acinar and ductal cells * crevicular fluid • The saliva is used as a diagnostic fluid, because the presence of BIOMARKERS. Crevicular fluid is a fluid that is produced in small amounts in the gingival sulcus, because blood is filtered through the insertion Components of crevicular fluid: epithelium. electrolytes and biomolecules such as enzymes, antibodies, antibacterial factors, plasma proteins and defensive cells such as macrophages, monocytes and lymphocytes, etc. A) Gingival groove where the crevicular fluid is ultrafiltered. B) Extraction of the crevicular fluid by piece of paper and collection in eppendorf tube DEFINITION OF BIOMARKERS Are biomolecules of diverse chemical nature that can be measured providing us with relevant information: a)about different types of diseases, b)to identify risk factors for the health of individuals and populations, c) about drug selection and, d) evaluation of the progression of the disease and its treatment. DIFFERENT BIOMARKERS PRESENT IN THE SALIVA Biomarker DNA RNA Proteins Metabolites, electrolytes Drugs and its metabolites Lipids Virus, Bacteria Cellular debris Diagnostic uses Genotyping, Bacterial infection, Diagnosing head and neck carcinomas Forensic studies Identification of bacteria and / or viruses Carcinomas of the head and neck Immunoglobulins: diagnosis of virus (HIV, hepatitis B and C) Antigliadin and IgA: celiac disease Mucins: detecting cavities, head and neck carcinomas p53: oral carcinoma Tumor markers: c-erbB-2 breast cancer Marker CA125: Cancer EGF growth factor: Cystic Fibrosis Hormone: insulin Apha-amylase: Stress Melatonine: Cyrcadian rhythm Cytokines and/or interleukines: Periontoditis Periontoditis, cystic fibrosis, radiation effects, lactic acid: tooth decay Monitoring drug abuse and its detection in the body Prostaglandin E2: cystic fibrosis; steroid hormones Cortisol: stress HIV, Hepatitis A and C, mumps, Candida, Helicobacter, Streptococcus, Shigella Diagnosis of head and neck carcinoma ROLE OF SALIVA IN DENTAL PLAQUE AND CARIES • Dental Plaque is a biofilm that covers all the oral structures. It is partly cellular, fundamentally bacterial, and partly acellular, from bacterial, salivary and dietary sources. SALIVA contributes to the first stage of bacterial plaque building up through the formation of the acquired pellicle, an acellular coating made up of salivary proteins and other macromolecules. Salivary prolin-rich glycoproteins mediate the bacteria adhesion to the teeth surface. • Dental caries is a chronic disease and a dynamic process, which occurs in the dental structure of the tooth in contact with microbial deposits, due to imbalance between the tooth structure and the SALIVA surrounding the plaque, resulting in a loss of minerals from the tooth surface. Clear signs of the caries are the localized destruction of hard tissues of the tooth. Caries is classified as a transmissible and irreversible disease. DENTAL CARIES AND Streptococcus mutants  The acidification of the oral cavity due to the fermentation of sugars will inhibit the growth of some bacteria allowing the Streptococcus to win the competence.  Streptococcus mutans have the glycosyltransferase enzyme and the fructosyltransferase to synthetize glucans and fructans using as a substrate sucrose molecules. GLUCANS and FRUCTANS: • Facilitate adherence of bacteria to enamel • Source of energy for bacteria Extracellular Matrix of Periodontal Tissues • Dentists are concerned with the structures of the oral cavity: the teeth, the oral mucosa, the periodontal tissue and the alveolar bone. Periodontum: consists of the gingiva , cementum, cementum, periodontal ligament, and surrounding alveolar bone. • The extracellular matrix of peridodontal tissues are variants of the matrix present in Connective Tissues. Extracellular Matrix (ECM) at a glance  The Extracellular matrix (ECM) is the non-cellular component present within all tissues and organs.  The ECM consists of water and a mixture of proteins (Collagen fibers and elastic Fibers, glycoproteins) and a ground substance (proteoglycans and GAG) produced by the endoplasmic reticula (ER) and Golgi apparatuses of nearby cells. )  The components of ECM are synthetized inside and secreted. Final organization of the ECM then takes place outside the cell. Basal lamina Ground substance Extracellular Matrix (ECM) at a glance FUNCTIONS: 1) Physical scaffolding for the cellular constituents 2) Initiation of Biochemical reactions needed for tissue morphogenesis, homeostasis and differentiation. 3) Participate in regulation of activity of those cells, influencing their shape, development, migration, proliferation, and metabolic functions. TISSUE DISTRIBUTION: • Epithelial tissue and nervous tissue have low extracellular matrix, while it is very important in connective tissue and in dental tissues. • Basal Lamina: Thin mat of extracellular matrix that separates epithelial sheets, and many other types of cells such as muscle or fat cells, from connective tissue. Serves as a support and attachment point for tissues. COMPONENTS of Extracellular Matrix in animal tissues COLLAGEN PROTEINS FIBROUS GLYCOPROTEINS FIBRONECTIN, INTEGRINS LAMININ ELASTIN FIBRILLAR STRUCTURE ADHESION CELL-ECM BASAL LAMINA ELASTIC STRUCTURE HYALURONIC ACID GLYCOCONJUGATES GROUND SUBSTANCE PROTEOGLYCANS GLYCOSAMINOGLYCANS (GAGs) COLLAGEN COLLAGEN: Collagen is the major protein of ECM in vertebrates. Two type of organization or polymerization: a) It may be fibrillary: types are I, II, III, V and XI. Type I is the most frequent: 90% of body collagen. b) Or non-fibrillary: Type IV, present in the basal lamina. Fibrous collagen forms filaments, microfibrils and fibers in ascending order of size and molecular complexity. FUNCTION: Collagen interacts with other proteins, glycans and proteoglycans to build calcified and uncalcified tissues and organs. Calcified collagen fibers are present in Bone, dentin, and cementum. Uncalcified collagen fiber bundles, and collagen calcified in cementum and bone are the major components of the gingiva and periodontium. The ends of the collagen fibers of the periodontal ligament are embedded in calcified cementum and bone to anchor the tooth into the ALVEOLAR BONE. Collagen fibers in the gingiva provide structural support to the gingival tissue and maintain the alignment of the teeth. COLLAGEN type IV IN THE BASAL LAMINA Basal lamina: Thin mat of extracellular matrix that separates epithelial sheets, and many other types of cells such as muscle or fat cells, from connective tissue. Serves as a support and attachment point for tissues. N-terminal Globular domain No helical Triple helix C-terminal Globular domain Monomer of collagen IV Structure more flexible than collagen fibrils Globular domains at both ends Association dimer Tetramer Unlike most collagens, once released into the extracellular space does not degrade its ends, it allows the connection of these ends with other molecules of the same type of collagen, resulting in extracellular associations in the form of dimers, tetramers and higher order, forming a network. Interactions between globular domains FIBRONECTIN: Play an important role in adhesion between cells and ECM Glycoprotein present in the ECM of most animals tissues. It is a dimer composed of two very large monomers joined by disulfide bridges at C-terminal end (integrin interactions) and N-term interaction with collagen fibrils It is present in basal lamina of epithelial and endothelial tissues INTEGRINS ROLE: CONEXIONS BETWEEN CELLS-BASAL LAMINA AND CELL MATRIX ECM Integrins are transmembrane receptors that facilitate cell-extracellular matrix (ECM) adhesion. Upon ligand binding, integrins activate signal transduction pathways that mediate cellular signals such as regulation of the cell cycle and organization of the intracellular cytoskeleton LAMININ Play an important role in adhesion between cells and the basal lamina. Binds to collagen and sulfate lipids The coiled-coil α-helix maintains the 3 chains covalently bond through disulfite bonds Binds to carbohydrates and integrins Binds to collagentype IV Binds to sulfate lipids The subunits of a laminin-1 molecule. This multidomain glycoprotein is composed of three polypeptides (α, β, and γ) that are disulfide-bonded into an asymmetric crosslike structure. With different functional domains that bind to cell-surface receptors and other components of ECM (collagen type IV, heparan sulfate). ELASTIC FIBERS: ELASTIN AND OXYTALAN ELASTIN Many vertebrate tissues, such as skin, blood vessels, and lungs, need to be both strong and elastic in order to function. Two domains: 1: Hydrophobic domain that forms extracellular extensible fibres (elastic fibers) that give tissues their stretchability and resilience 2. Domain rich in alanine and lysine  responsible of covalent unions between neighbor proteins. ELASTIC FIBER FIBRILIN ELASTIN The elastic fiber contains a core of elastin protein embebbed in microfibrils of the glycoprotein fibrilin. ELASTICITY Fibers can stretch up to 150% of their length, without breaking and recoil afterwards. The molecules are joined together by covalent bonds (red) to generate a cross-linked network. Each elastin molecule in the network can expand and contract as a random coil, so that the entire assembly can stretch and recoil like a rubber band. ELASTIC FIBERS IN PERIODONTAL LIGAMENT Periodontum: consists of the gingiva , cementum, cementum, periodontal ligament, and surrounding alveolar bone. Group of tissues that support and protect the tooth The periodontal fibers of the periodontal ligament are primarily composed of bundles of type I COLLAGEN fibrils. In addition to the collagen fibers, the periodontal ligament also contains OXYTALAN fibers that are related to the microfibrillar component of elastic fibers. They allow the periodontum to support the movement of teeth during mastication and support vessels of the periodontal ligament. ELASTIC FIBERS IN PERIODONTAL LIGAMENT COLLAGEN FIBERS OXYTALAN FIBERS Bundles of oxytalan fibers Cement Periodontal vessels Oxytalan: inmature elastic fibers = microfibrils without elastin. They generally run parallel to the teeth root surface, although they can occasionally insert into cementum. Oxytalan fibers Dentin Alveolar bone Periodontal Ligament GLYCOSAMINOGLYCANS AND GLYCOCONJUGATES of Extracellular Matrix GLYCOSAMINOGLYCANS (GAGs) -HYALURONIC ACID -CHONDROITIN SULFATE -HEPARAN SULFATE -KERATAN SULFATE -DERMATAN SULFATE PROTEOGLYCANS GAGs + PROTEINS GLYCOSAMINOGLYCANS AND GLYCOCONJUGATES of Extracellular Matrix GAGs • Disaccharide repetitions • They all have sulfate groups, except hyaluronic acid • Hydrophilic molecules • Negative charge • Attract large amounts of water • Hydrated gels that expand through the extracellular space GAGs enable a rapid diffusion of water-soluble substances and migration of cells through the matrix. Hyaluronic acid Polymer of: glucoronic acid and N-acetylglucosamine joined by β bonds Hyaluronan (also called hyaluronic acid or hyaluronate) is the simplest of the GAGs, consists of a single long chain of up to 25,000 sugars. The other GAGs are smaller (150 dimers). In contrast with all of the others, it contains NO sulfated sugars, all its disaccharide units are identical, its chain length is enormous, and it is not generally linked covalently to any core protein. It is involved in the cell migration during development and lesion repair. The most abundant GAG in periodontal tissue, in elevated concentrations in gingival tissue. It participates in the repair of tissues after a gingivitis or dental interventions PROTEOGLYCANS • They are macromolecules of the cell surface and extracellular matrix containing one or more chains of GAGs covalently attached to a membrane or a secretory protein. • Play an important role in tissue resilience and filtering GAGs - CHONDROITIN SULFATE - HEPARAN SULFATE - KERATAN SULFATE - DERMATAN SULFATE + PROTEIN Proteoglycans types: Syndecans: member of the membrane heparan sulfate proteoglycan family, with a single transmembrane domain and a extracellular domain. Glypicans: attached to membrane by a lipid anchor, a derivative of the membrane lipid phosphatidylinositol Aggrecans: supramolecular assemblies of many core proteins bound to a single molecule of hyaluronan. Proteoglycans aggregates. Proteoglycans types: Aggrecan: Present in extracellular matrix, interacts with collagen in cartilage, contributing to development, tensil strengh and resiliency of this connective tissue. They interact with other proteins (elastin, fibronectin…) giving strenght and resilience to extracellular matrix. Also they intervine in cell signaling. Associates with water which hydrates the molecule occupying a volume similar to that of bacterial wall AGGRECAN FORMS AN AGGREGATE WITH HYALURONIC ACID AND LINK PROTEIN DENTAL APPLICATIONS DEGRADATION OF BASAL LAMINA AND EXTRACELLULAR MATRIX ECM PROTEINS: Collagen, Fibronectin, Elastin, Laminin GAGs, Proteoglycans, hyaluronic acid METALLOPROTEASES (MMPs) The proteolytic enzymes called metalloproteases are involved in the degradation of the ECM in all tissues of the body, including mesenchymal tissue, bone, enamel and dentin. They are proteases that participate in the degradation of collagen, laminin and fibronectin. They are secreted to function outside the cell. FUNCTION OF METALLOPROTEASES The regulated turnover of extracellular matrix macromolecules is crucial to a variety of important biological processes.  Tissue modification after its function has finished: Rapid degradation occurs, for example, when the uterus involutes after childbirth, or when the tadpole tail is resorbed during metamorphosis  Localized tissue degradation: A more localized degradation of matrix components is required when cells migrate through a basal lamina. This occurs when white blood cells migrate across the basal lamina of a blood vessel into tissues in response to infection or injury, and when cancer cells migrate from their site of origin to distant organs via the bloodstream or lymphatic vessels—the process known as metastasis. Even in the seemingly static extracellular matrix of adult animals, there is a slow, continuous turnover, with matrix macromolecules being degraded and resynthesized. Most are matrix metalloproteases, which depend on bound Ca2+ or Zn2+ for activity; the others are serine proteases, which have a highly reactive serine in their active site. Periodontal disease Any disease, gingivitis or periodontitis, affecting the periodontium. It is characterized by a chronic inflammatory destructive process affecting the tissues supporting the teeth. GINGIVITIS Gum Inflammation, which commonly occurs because a film of plaque, or bacteria, accumulates on the teeth. Bacteria in plaque around the teeth release enzymes (collagenases) that can damage and erode the gum tissues. The infected gums swell, bleed easily, recede, and loosen from the teeth. Tooth loss is caused more frequently by gum disease than tooth decay. Normal gum Moderated gingivitis Advanced gingivitis Periodontal disease PERIODONTITIS Gum disease in which the periodontal attachment is destroyed, resulting in loose teeth that may exfoliate. Proteolytic enzymes (MMPs) play a vital role in periodontal connective tissue destruction and remodeling in the periodontal ligament MMPs x DESEQUILIBRIUM: Specific inhibitors (TIMP) TISSUE MMPs INFLAMMATION DESTRUCTION Leukocyte recruitment Release of inflammatory mediators and cytokines BACTERIA PERIOODONTOPATHOGENS Sources of MMPs: BACTERIA FIBROBLASTS ENDOTHELIAL CELLS NEUTROPHILS LEUKOCYTES