Collagen Structure , ans synthesis

ppt on collagen

1. COLLAGEN DR RIPUNJAY TRIPATHI POST GRADUTE STUDENT DEPT OF PERIODONTOLOGY

2. CONTENTS … Introduction Structure /Chemical Comp. of collagen Type of collagen Synthesis of collagen Collagen in periodontium Functional adaptation of collagen in periodontium Degradation and remodelling Diseases of collagen related to periodontium Conclusion

3. INTRODUCTION Collagen is a family of highly developed fibrous proteins found in all multicellular animals. It is the most abundant proteins found in mammals, constituting 25 percent of the total protein mass . Collagen is the main fibrous component of skin, bone ,tendon, cartilage and periodontium . It comprises about 90% of the organic matrix of the bone. Collagen is a natural protein that provides our bodies with structural support.

4. Today, the intercellular substance of tissue, or the extracellular matrix, is recognized as a complex, interactive compilation of proteins in dynamic equilibrium that can regulate the gene expression of cells. The predominant extracellular matrix component of the periodontium is collagen, a genetically distinct super family of extracellular macromolecules that contain one or more triple-helical domains. There are as many as 25 different genes that code for at least 14 different collagen molecules Six different collagen types have been detected in the periodontium

5. EXTRACELLULAR MATRIX ( Periodontium ) FIBROUS + GROUND STRUCTURE Non Collagenous proteins Proteoglycans, Hyaluronan Lipids , Water (Provides Compressive Strength) Collagen Elastin Oxytalin Elauin (PROVIDES TENSILE STRENGTH )

6. A few Physiological Roles of Collagen Rigid rod like structure that resists stretching of the cell and provides a high tensile strength Transmits mechanical forces preventing any loss or tear of ligaments Therefore this protein is an important structural component in tissues such as the periodontal ligament and muscle tendons in which the mechanical forces need to be transmitted

7. Influences cell shape , size & migration

8. STRUCTURE All collagens are composed of 3 polypeptide alpha chains coiled around each other to form the tripe helix configuration. The individual polypeptide chains of collagen each contain app. 1000 amino acid residues .

9. An alpha-triple helix of collagen is shaped into a right handed helix . The Alpha chains each are shaped into a left-handed symmetry (i.e. the opposite way round), and then three of these coiled strands get together and form a right-handed triple helix of collagen. Depending upon the type of the collagen , the molecule may be made up of either 3 identical Alpha chains( homotrimers ), or two or three different alpha chains( heterotrimers ). ALPHA HELIX OF COLLAGEN

10. The α chains are left handed helices that wrap around each other into a right handed rope like triple helical rod. Each such helix is around 1.4 nanometers in diameter and 300 nanometers in length The triple helix may be of continuous stretch or interrupted by non collagenous elements

11. Glycine occupies every third position in the repeating amino acid sequence GLYCINE-X-Y AMINO ACID SEQUENCE Collagen is rich in Proline , Hydroxyproline and Glycine

12. Proline helps in the formation of helical orientation of each alpha chain Glycine The smallest amino acid found in every 3rd position in the polypeptide chain - GLY-X-Y------------------GLY-X-Y- X- Proline Y - Hydroxy proline Hydroxy lysine

13. Proline frequently occupies the X position. Hydroxyproline and hydroxylysine are two unique amino acids. Vertebrate collagens exhibit the two of them in the Y positions Each collagen molecule is stabilized through lysine derived intra and intermolecular cross links. Each α chain comprises of around 1056 amino acids. There are around 3 amino acids per turn

14. HYDROXYPROLINE AND HYDROXYLYSINE Extra Capacity for Hydrogen Bonding. Prevents denaturation of collagen fibers in temperature changes. Non hydroxylated triple helices have been shown to undergo denaturation at temperatures below 37*C. Collagen has Hydroxy Proline & Lysine that are not Present in many other proteins. Hydroxy Proline : Stabilizes Triple Helical Structure

15. TYPES OF COLLAGEN 19 different collagen types have been discribed so far..... Many genetically, chemically, and immunologically distinct types of collagen have been identified.

16. Variations are due to …. Differences in the assembly of basic polypeptide chains Different lengths of the helix Various interruptions in the helix and Differences in the terminations of the helical domains

17. Collagens are divided roughly into 3 groups based on their abilities to form fibrils. They are as follows…. 1.Fibrils forming protein Form banded fibrils Type I Type II Type III Type V Type XI

18. 2.Fibril associated collagens with interrupted triple helices ( FACIT ) This group of collagens consists of proteins in which collagenous domains are interrupted by non collagenous sequences . These are associated with the surface of fibril forming collagens. Includes type IX, type XII, type XIV and perhaps type XVI also. The former three are unique in containing glycosaminoglycan components covalently linked to the protein molecule.

19. 3)All other non fibrillar collagens form the third group which includes Type IV, type VIII and type X ( network forming collagens ) Type VI ( beaded fibril forming collagen ) Type VII ( anchoring fibrils and invertebrate cuticle collagen ) In addition to the above collagen groups at least 10 non collagenous proteins incorporating short triple helical collagen domains have been described

20. 4)This group of collagen domain containing non matrix protein molecules includes (10 Non Collagenous Proteins) C1q component of C1 complement Lung surfactant protein Acetylcholine esterase Conglutinin Mannose binding protein These proteins are not considered true collagens because they do not form a part of the extracellular matrix.

21. COLLAGEN IN PERIODONTIUM AND TOOTH STRUTURES COLLAGEN IN PERIODONTIUM The collagen of PDL is largely Type I , with lesser amounts of type III , IV , VI and XII . Collagen fibers of the periodontium ( particularly Type I ) provide the structural requirements to withstand intrusive forces of mastication ( tooth support ) and also to accommodate growing tooth in mammals.

22. DENTIN COLLAGEN It has been found that type I collagen with the structure [α1 (I) α2 (I) ] was the most exclusive collagen in dentine and predentine Demineralized dentine and predentine show closely packed collagen fibers of 20-50nm Dentinal collagen contains 2-3 fold increase of hydroxylysine compared to that of soft tissues. Dentinal collagen is relatively insoluble in acid and neutral solutions The only other collagen synthesized in culture by odontoblasts is type V collagen which is secreted into predentine ( only 3%).

23. CEMENTAL COLLAGEN The amino acid composition of human cemental collagen resembles that of type I collagen. 5% of type III collagen is accounted for the Sharpey’s fibers that are a part of the periodontal ligament. Major cross link is dehydrodihydroxylysinonorleucine (DHLNL) The other cross link is dehydrohydroxylysinonorleucine (HLNL).

24. PULPAL COLLAGEN Approximately 34% dry weight of pulp is collagen There is higher content of collagen in the radicular areas compared to the pulp chambers and higher concentration in the middle and apical portion of the root compared to the rest of the tooth After a small increase in collagen synthesis which occurs at the time of eruption and root closure, there is no change in collagen content of the tooth for rest of the life

25. BONE COLLAGEN It contains type I collagen predominantly with the molecular configuration of [α1 (I) α2 (I)]. During its formation in the osteoblast the large procollagen precursor undergoes important post translational modifications. Suitably located proline and lysine residues are hydroxylated to hydroxyproline and hydroxylysine respectively The collagen of bone has less diglycosylated hydroxylysine than that of skin. The ratio of glycosyl-galactosyl hydroxylysine to galactosyl hydroxylysine is 0.47 in bone compared to 2.06 in skin

26. GINGIVAL COLLAGEN Collagens are the most abundant biochemical constituents of gingival CT(90%). The collagen matrix of gingival CT is well organized into fiber bundles, which constitute the gingival supra alveolar fiber apparatus. Based on their preferential orientation, architectural arrangement and sites of insertion they are classified as :

27. 1.Dentogingival 2.Dentoperiosteal 3.Alveologingival 4.Periosteogingival 5.Circular and semicircular 6.Transgingival 7.Transseptal 8.Interpapillary 9.Intercircular 10.Intergingival

28. PERIODONTAL FIBRES It contains type I and type III collagen. Relative proportion of type III to type I varies from 10-25% Type III collagen fibers are smaller in diameter and appear to withstand deformation better than type I. It also helps reduce fibril diameter with type I. Type IV is found in the basement membranes and type V with cell surfaces(0.1-0.2%). Major crosslink is of dihydroxylysinonorleucine while hydroxylysinonorleucine is a minor component

29. PRINCIPAL FIBRES OF THE PERIODONTAL LIGAMENT

30. SHARPEY FIBRES Collagen are arranged in bundles and they form the Principal Fibers . The terminal ends of the collagenous principal fibers are inserted in to bones to form Sharpey Fibers. At their insertion the collagen bundles of PDL are embed in to cementum and alveolar bone in a manner similar to tendon inserting in to the bone . They usually tend to be concentrated in the crestal region. Some Sharpey fibers pass right through alveolar bone , which implies that there may be continuity between the collagen fibers of the PDL of adjacent teeth . ( Transalveolar Fibers ) Sharpey Fibers are enclosed within a sheath of collagen Type III and it not only confers elasticity on the fibers but it also maintains the elasticity of the fibers when they are inserted in to the bone by preventing their mineralization.

31. ELASTIC FIBERS OF PDL In PDL the collagen fibers are associated with elastic mesh work which may function either as a static elastic element or as a resilient material. The 3 fibrous components are OXYTALAN , ELAUNIN & ELASTIN. Oxytalan fibers form a 3D meshwork that extends from the cementum to the periodontal blood vessels. The size of the fibers vary depending on the site. A- CEMENTUM B- OXYTALAN FIBRES C- OXYTALAN TRACT D- PERIODONTAL VESSEL

32. It is oriented in the Apico Occlusal plane . Oxytalan & Elaunin Fibers are precursors of the elastin fibres . Oxytalan fibers are composed of microfilaments surrounded by amorphous material. Elastin fibers are composed of microfibrillar glycoprotein and amorphous elastin . Elementary units of elastin are Rod-Like in shape . Elastin fibers are found only in the PDL of some species.

33. BIOSYNTHESIS Sites For The Synthesis of Collagen : 1.Mesenchymal Cells & Their Derivatives FIBROBLASTS ( major cells ) Chondrocytes Osteoblasts Odon oblasts Cementoblasts 2.Other Cells : Epithelial cells. Endothelial cells. Muscle cells. Schwann cells.

34. SYNTHESIS OF COLLAGEN

35. The entire process of collagen synthesis can be best understood under the following stages … Gene Expression Translational and post translational events or intracellular steps in collagen synthesis procollagen formation Extracellular collagen biosynthetic events extracellular Regulation of synthesis NUCLEUS CYTOPLASM EXTRACELLULAR

36. INTRA NUCLEAR STEPS The 3 polypeptide chains of collagen molecule are formed separately under the direction of their respective genes. The initial RNA transcript is processed to mRNA. After Nuclear steps the mRNA translocates to cytoplasm where it binds to ribosome to get translated & codes for PreProCollagen . CYTOPLASMIC STEPS Pre Pro collagen Cleavage of Signal Peptide PROCOLLAGEN α CHAIN Hydroxylation Glycosylation Association C terminal Peptides Disulphide Bond Formation PROCOLAGEN MOLECULE Passes in to golgoi complex combines with Secretory Vacuoles to move outside cell .

37. EXTRACELLULAR STEP REMOVAL OF TERMINAL PRO PEPTIDES Cleavage of C & N Pro peptides by C & N Proteinase . ASSEMBLY OF COLLAGEN The collagen molecules then align themselves laterally to each other , having a quarter over-lap such that there is typical 64nm banded appearance. These fibrils are immature and lack strength CROSS LINK OF FIBRILS TO FORM FIBRES Cross-linkage is a slow process and the tensile strength of collagen steadily increases over a long period

38. REGULATION OF COLLAGEN SYNTHESIS Collagen biosynthesis is tightly regulated during normal development & homeostasis in a cell & tissue specific manner . POST TRANSLATIONAL MODIFICATION GENE TRANSCRIPTION

39. FUNCTIONAL ADAPTATIONS OF COLLAGEN IN PERIODONTIUM Tooth support system is a multiphasic system comprising of fibres , ground substances,blood vessels,fluids acting together to resist mechanical forces. MECHANICAL FORCES Axially & laterally directed Tension & Compression Majority of PDL collagen fibers are arranged in to Horizontal & Oblique directed groups to adapt to axial forces. OVERLAPPING ARRANGEMENT This overlapping arrangement is very crucial in withstanding Rotational & Intrusive Forces

40. Degradation of Collagen Break down of the collagen matrix element is a key component of any normal tissue that is undergoing morphogenesis and growth. But it is vital that this process is kept under rigid control. Collagen Degradation by MMPS Collagen Denatured Four types of proteolytic enzymes, capable of ECM degradation Matrix metalloproteinases ( MMPs ) Serine proteinases ( e.g . plasmin ) Cysteine proteinases ( e.g . cathepsin K) and Aspartic

41. The MMPs are considered to be essential for the degradation The collagenases are responsible for the first degradation step of collagen Gelatinases and cysteine proteases further degrade the collagen fragments COLLAGEN DESTRUCTION IN INFLAMMATION GINGIVITIS :- In initial lesion – perivascular loss of collagen can be seen. In early lesion - increase in the amount of collagen destruction is seen, 70% of collagen is destroyed around the cellular infiltrate In established lesion – collagen fibers are destroyed around the infiltrate of intact and disrupted plasma cells, neutrophils, lymphocytes, monocytes and mast cells. PERIODONTAL POCKET :- Apical to the junctional epithelium, collagen fibers are destroyed .

42. AGE CHANGES IN COLLAGEN

43. As age advances qualitative and quantitative changes of collagen are seen -Higher conversion of soluble to insoluble collagen -Increased mechanical strength. - More organized and thicker. - Areas of hyalinization. -Increased denaturing temperature - Apparent decrease in the number of collagen & PDF fibers due to Increased Fibrosis+ decreased cellularity . - Gradual decrease in the number of synthesizing connective tissue cells - A gradual recession of alveolar bone. Irregular Alveolar Bone & cementum surface. These changes are due to higher cross linking and stabilized forms of collagen

44. COLLAGEN AS BIOMATERIAL IN PERIODONTICS Drug delivery- For LDD in periodontal pockets Tissue augmentation- recession coverage Collagen membranes are used as an alternative to connective tissue grafts in mucogingival surgeries Bone substitute- as bone grafts in intra-bony defects Collagen has been used as implantable carriers for bone inducing proteins Collagen itself is used as bone substitutes due to its osteo -inductive activity. Osseograft /DMBM is one such de-mineralized bone derived Type-I collagen for bone void filling applications

45. COLLAGEN DISORDERS Collagen diseases may be genetic, auto-immune or miscellaneous like defects due to nutritional deficiencies, drug induced defects etc. OSTEOGENESIS IMPERFECTA EHLER-DANLOS SYNDROME

46. ALPORT SYNDROME EPIDERMOLYSIS BULLOS SYSTEMIC LUPUS ERYTHEMATOSUS SCURVY ORAL SUBMUCOUS FIBROSIS

47. CONCLUSION Mechanisms that regulate collagen synthesis have a direct bearing on periodontal structures in which the connective tissues specially collagen undergo dynamic changes during periodontitis and drug-induced gingival hyperplasia A balanced synthesis , regulation and degradation of collagen ensures a healthy periodontal health. Most diseases in higher animals involve collagen containing connective tissue directly/indirectly

48. REFFERANCES Shrutal Narendra et al. Enigmatic insight into collagen J Oral Maxillofac Pathol . 2016 May-Aug; 20(2): 276–283. Carranza’s. Clinical Periodontology. 12 th ed.New Delhi:Elsevier ;2015. pp. 17, 23-24 ch.-1 Nanci A. Ten Cate's Textbook of Oral Histology, Development, Structure & Function. 7th ed. New Delhi: Elsevier; 2008. pp. 66–8. Ch. 4 Shafer WG, Hine MK, Levy BM. A Textbook of Oral Pathology. 4th ed. Noida: Elsevier Saunders Publication; 2009. pp. 109–10. Neville BW, Damm DD, Allen CM, Bouquot JE. Oral & Maxillofacial Pathology. 2nd ed. Noida: Elsevier Saunders Publication; 2008. pp. 349–50

49. Stenzel et al . Collagen as a biomaterial . Annu Rev Biophys Bioeng . 1974;3:231–53. Pintippa et al. Collagen members : A Review . J Periodontol . Feb 2001;72:215-29