PERIO

1. COLLAGEN

2. • INTRODUCTION
• STRUCTURAL FEATURES
• BIOSYNTHESIS
• TYPES AND TISSUE DISTRIBUTION
• DEGRADATION AND REMODELLING OF COLLAGEN
• FUNCTIONS OF COLLAGEN
• DISEASES/CLINICAL IMPLICATIONS
• CONCLUSION

3. - Cells are the basic units of life. Most mammalian cells are located in tissues
where they are surrounded by a complex extracellular matrix(ECM), often
referred to as the connective tissue .
- The extracellular matrix contains three major class of biologic molecules.
• Structural proteins such as collagen and elastin.
• Certain specialized proteins such as fibrillin,fibronectin and laminin.
• Proteoglycans which consists of glycosaminoglycans,formerly called as
mucopolysaccharides.

4. - The supramolecular arrangement of fibrillar elements, microfibrillar
networks as well as soluble proteins, glycoproteins and a wide range
of other molecules define the biophysical characteristics.
- The primary function of extracellular matrix is to endow tissues with
their specific mechanical and biochemical properties. Resident cells
are responsible for its synthesis and maintenance, but the extracellular
matrix, in turn, has also an impact on cellular functions.
- An additional influence of the extracellular matrix on morphogenesis
and cellular metabolism can be ascribed to the storage and release of
growth factors which is modulated by their binding to specific matrix
components

5. - The most abundant proteins in the extracellular matrix are members of
the collagen family.
- Collagens were once considered to be a group of proteins with a
characteristic molecular structure with their fibrillar structures
contributing to the extracellular scaffolding.
- Thus, collagens are the major structural element of all connective
tissues and are also found in the interstitial tissue of virtually all
parenchymal organs, where they contribute to the stability of tissues
and organs and maintain their structural integrity.

6. • Collagen – derived from the greek word – kolla(glue) and gene.
• Triple helical structure : Characteristic triple helix of three polypeptide
chains and all members of the collagen family form these supramolecular
structures in the extracellular matrix although their size, function and tissue
distribution vary considerably.
• Each of the three a-chains within the molecule forms an extended left-
handed helix with a pitch of 18 amino acids per turn. The α chains are left
handed helices that wrap around each other into a right handed rope like
triple helical rod.

7. structure
• 1.Presence of triple helical structure formed by alpha chains(RICH
,CRICK AND NORTH-1955)
• 2.Glycine occupies every third position in amino acid sequence (Gly –
X – Y)
• 3.Contains unique amino acids hydroxylysine and hydroxyproline.
• 4.Collagen is stabilized by lysine derived intra and intermolecular
cross-links

10. α-Helix
• α-Helix is the most common spiral
structure of protein
• The salient feature: The α-Helix is a
tightly packed coiled structure with
amino acid side chains extending
outward from the central axis.
• The α-Helix - stabilized by extensive
hydrogen bonding

11. BIOSYNTHESIS
• Involved in tissue differentiation, growth and remodeling
• Young tissue has high rate of collagen synthesis
• As the tissues matures in adults, synthesis continues as a part of
normal tissue turnover
• Highest rate of collagen turnover are observed in weight bearing
bones, lungs and periodontal tissues
• Collagen synthesis is elevated under conditions requiring remodeling
and replacement of tissues and during tissue repair
• Elevated rates in pathological conditions such as fibrosis in lungs and
liver

12. Collagen Synthesizing Cells
• Synthesized by cells of mesodermal origin, collectively referred to as fibroblast
• In highly differentiated state these fibroblast acquire characters especially suited
to the chemistry of the tissues
• Chondroblast in cartilage
• Odontoblast in teeth
• Osteoblast in bone

13. • Collagen synthesizing cells
contains extensive RER and well
developed Golgi apparatus
• Synthesized in RER, passed into
Golgi and secreted into
extracellular space.

14. STEPS
Intracellular
synthesis of collagen mRNA
Peptide Synthesis
Hydroxylation of proline and lysine
glycosylation of hydroxylysine
Disulfide bond
Secretion of Procollagen
(Triple helical)
Req Vit C

15. Extracellular
Extracellular procollagen
Collagen molecule
collagen fibril
Mature fibrous collagen
Peptide cleaved off
Aggregation
Lysyl oxidase
Cross-linking

17. Mediators that affects collagen synthesis

20. TYPES AND TISSUE DISTRIBUTION
• So far, 28 genetically distinct collagen types have been described.
Based on their structure and supramolecular organization, they can
be grouped into :
- fibril-forming collagens
- fibril-associated collagens (FACIT)
- network- forming collagens
- anchoring fibrils
- transmembrane collagens
- basement membrane collagens and others with unique functions.

23. THE FIBRIL FORMING COLLAGENS
• Collagen types I, II, III, V and XI.
• Characterized by their ability to assemble into highly orientated
supramolecular aggregates with a characteristic suprastructure, the typical
quarter-staggered fibril-array with diameters between 25 and 400 nm.
• In the electron microscope, the fibrils are defined by a characteristic
banding pattern with a periodicity of about 70 nm (called the D-period)
based on a staggered arrangement of individual collagen monomers.

24. - The triple helix is usually formed as a heterotrimer by two identical
a1(I)-chains and one a2(I)-chain. The triple helical fibres are, in vivo,
mostly incorporated into composite containing either type III collagen
(in skin and reticular fibres) or type V collagen (in bone, tendon,
cornea)
• Type I collagen provides tensile stiffness and in bone, it defines
considerable biomechanical properties concerning load bearing, tensile
strength, and torsional stiffness in particular after calcification.

26. • Type II collagen
• The characteristic and predominant component of hyaline cartilage.
• The triple helix of type II collagen is composed of three a1(II)-chains
forming a homotrimeric molecule similar in size and biomechanical
properties to that of type I collagen.
• Collagen fibrils in cartilage represent heterofibrils containing in addition to
the dominant collagen II, also types XI and IX collagens which are
supposed to limit the fibril diameter to about 15–50 nm as well as other
non-collagenous proteins.

27. • Type III collagen
• Type III collagen is a homotrimer of three a1(III)-chains and is widely
distributed in collagen I containing tissues with the exception of bone.
• It is an important component of reticular fibres in the interstitial tissue
of the lungs, liver, dermis, spleen, and vessels.
• This homotrimeric molecule also often contributes to mixed fibrils
with type I collagen and is also abundant in elastic tissues.

28. • Types V and XI collagens are formed as heterotrimers of three different
a-chains (a1, a2, a3).
• the a3-chain of type XI collagen is encoded by the same gene as the a1-
chain of type II collagen and only the extent of glycosylation and
hydroxylation differs from a1(II).
• Types V and XI collagens form a subfamily within fibril-forming
collagens,(a combination between different types V and XI chains appears
to exist in various tissues) though they share similar biochemical properties
and functions with other members of this family.

29. Collagen types IX, XII, and XIV—The FACIT collagens
• The collagen types IX, XII, XIV, XVI, XIX, and XX belong to the so-called Fibril-
Associated Collagens with Interrupted Triple helices (FACIT collagens).
• The structures of these collagens are characterized by ‘‘collagenous domains’’ interrupted
by short non-helical domains and the trimeric molecules are associated with the surfaces
of various fibrils.
• presumably play a role in regulating the diameter of collagen fibrils.
• Collagen type IX co-distributes with type II collagen in cartilage and the vitreous body .
The heterotrimeric molecule consists of three different achains (a1(IX), a2(IX), and
a3(IX)) forming three triple helical segments flanked by four globular domains (NC1–
NC4).

30. • Type IX collagen molecules are located periodically along the
surface of type II collagen fibrils in antiparallel direction. This
interaction is stabilized by covalent lysine-derived cross-links to the
N-telopeptide of type II collagen.
• A hinge region in the NC3 domain provides flexibility in the molecule
and allows the large and highly cationic globular N-terminal domain to
reach out from the fibril where it presumably interacts with
proteoglycans or other matrix components. Additionally, collagen type
XVI is found in hyaline cartilage and skin and is associated with a
subset of the collagen ‘‘type II fibers’’ (Graessel).

31. • Types XII and type XIV collagens are similar in structure and
share sequence homologies to type IX collagen. Both molecules
associate or colocalize with type I collagen in skin, perichondrium,
periosteum,tendons, lung, liver, placenta, and vessel walls.

32. • Collagen type VI—a microfibrillar collagen
• Type VI collagen is an heterotrimer of three different a-chains (a1, a2, a3)
with short triple helical domains and rather extended globular termini. This
is in particular true for the a3-chain which is nearly as twice as long as the
other chains due to a large N- and C-terminal globular domains.
• However, these extended domains are subject not only to alternative
splicing, but also to extensive posttranslational processing, both within and
outside the cell. The primary fibrils assemble already inside the cell to
antiparallel, overlapping dimers, which then align in a parallel manner to
form tetramers.

34. - Type VII collagen is the predominant component of the anchoring fibrils of basement
membranes.
- Secreted in a soluble form by basal epithelial cells
- Composed of a central helical portion with a globular domain at the C-terminal and a
small nonhelical domain at the N-terminal.
- These triple helical molecules align at the C-terminus as antiparallel dimers of
approximately 450 nM each in length. One end of the molecule becomes embedded in the
lamina densa of the basement membrane, where it interacts with type IV collagen, and the
other end attaches to anchoring plaques.
- Type VII collagen has been localized in the basement membrane of gingival oral
epithelium

35. • Types I and V collagen - the structural backbone of bone
• Types II and XI collagens - the fibrillar matrix of articular cartilage. Their torsional stability and
tensile strength lead to the stability and integrity of these tissues.
• Type IV collagens -basement membranes.
• Type VI collagen - highly disulfide cross-linked and contributes to a network of beaded filaments
interwoven with other collagen fibrils.
• Fibril-associated collagens with interrupted triple helices (FACIT) such as types IX, XII, and XIV
collagens - presumably play a role in regulating the diameter of collagen fibrils.
• Types VIII and X collagens - form hexagonal networks while others (XIII and XVII) even span
cell membranes.

36. GINGIVA
• Type I collagen is the main collagen species in all layers of gingival connective tissues.
• The collagen fibers are arranged in two patterns of organization, one consisting of large,
dense bundles of thick fibers(Type I collagen is preferentially organized into denser fibrils
in the lamina propria.)
• and the other, a loose pattern of short thin fibers mixed with a fine reticular network.
These fibers contain both type I and III collagens.
• Although it is not restricted to any particular region, type III collagen appears to be
preferentially localized as thinner fibers in a reticular pattern near the basement
membrane at the epithelial junction. Type III collagen has a more diffuse pattern in lamina
propria.

37. PERIODONTAL LIGAMENT
• The fibroblast is the predominant cell of the PDL.They are regularly distributed throughout the
ligament and are oriented with their long axis parallel to the direction of collagen fibrils.
• They have the ability to synthesize and shape of proteins of the ECM in which collagen fibrils
form bundles that insert into the tooth as Sharpey’s fibres.
• The collagen of periodontal ligament is Type I (80%), type III (20%) with lesser amounts of Type
IV, V, VI & XII also present.
• The collagen fiber bundles in the ligament and the fibers of Sharpey are mainly composed of
interstitial collagens I and III, which form banded fibrils.

38. • Type III collagen is more fibrillar and extensible than type I and may be
important in maintaining the integrity of the ligament during the small
vertical and horizontal movements which occur during chewing.
• The principal fibers are composed mainly of collagen type I, whereas
reticular fibers are composed of collagen type III. Collagen type III
generally co-distributes with collagen type I to form mixed fibrils of
infinitely varying proportions, a higher proportion of collagen type III is
present in fetal tissue.
• Collagen type IV is a short chain molecule that has only recently been
located in the periodontal ligament.

39. • Type III collagen is more fibrillar and extensible than type I and may be
important in maintaining the integrity of the ligament during the small
vertical and horizontal movements which occur during chewing.
• The principal fibers are composed mainly of collagen type I, whereas
reticular fibers are composed of collagen type III. Collagen type III
generally co-distributes with collagen type I to form mixed fibrils of
infinitely varying proportions, a higher proportion of collagen type III is
present in fetal tissue.
• Collagen type IV is a short chain molecule that has only recently been
located in the periodontal ligament.

40. • Collagen VI is a microfibrillar component, not directly associated with the major
banded collagen fibrils (but with the oxytalan fiber system),collagen XII belongs
to the fibril-associated collagens with interrupted triple helices that contribute to
the construction of the three-dimensional fibril arrangement.
• Temporal and spatial expressions of collagens I and XII in the remodeling
periodontal ligament during experimental tooth movement suggest that collagen
XII is closely associated with regeneration of periodontal ligament function.
• Besides collagens, several other proteins occur in the extracellular matrix of the
ligament that may have a relationship with the macromolecular organization.

41. BONE
• Collagen comprises the major (80–90%) organic component in mineralized bone
tissues.
• Type I collagen + type V collagen heterotypic fiber bundles that provide the
basic structural integrity of connective tissues.
• Along with type I and V collagens in alveolar bone, both type III and XII
collagens are also present.
• The type III collagen is present as mixed fibers with type I collagen in Sharpey’s
fibers that insert from the periodontal ligament into the lamellar bone lining the
alveolus to provide a stable connection with the tooth.

42. CEMENTUM
• Cementum is approximately 45 to 50% hydroxyappatite (inorganic) and 50%
collagen and non collagenous matrix proteins (organic).
• Collagen type I is the predominant collagen. It plays a key role in regulating
periodontal tissues during development and regeneration.
• In addition, during early stages of cementogenesis, development and repair, type
III collagen is present in high amounts but is decreased with maturation of this
tissue.
• Also, type XII collagen may assist in maintaining periodontal ligament space
versus continuous formation of cementum. Trace amounts of other collagens,
including type V and type XIV are also found in extracts of mature cementum.

43. COLLAGEN DEGRADATION AND
REMODELLING
• Degradation of collagen and other matrix elements is a key component
of normal tissue remodeling .
• However, extracellular matrix degradation also leads to pathologic
alterations.
• for example it is the major cause of connective tissue destruction in
periodontitis, rheumatoid arthritis and other chronic inflammatory
diseases.

44. • Though several other enzymes are involved in degradation of matrix
components ,collagen degradation is primarily mediated by collagenases.
• These enzymes have specifically evolved to hydrolyze collagens because
the triple helical collagen structure is resistant to most common proteinases.
The collagenases belong to a family of enzymes called Matrix
metalloproteinases (MMPs’).
• They are 13 in number each one having a 21kd catalytic domain that
contains Zn binding site.

45. • Based on their substrate specificity (Woessner et al 1991, Mignatti et al 1996 )
classified them into the following types
- Collagenases
- Gelatinases
- Stromelysins
- Matrilysins
• Three interstitial collagenases capable of degrading native matrix collagen fibrils
have been isolated and described so far.
• All of them cleave α1(I) and α2(I) chains at the glycine 775 – isoleucine 776
bonds respectively

46. • This results in release of cleavage fragments about three quarters and one quarter of the chain’s
original size.
• The released fragments have a lower Tm than the intact collagen molecule at the physiologic
temperature ,therefore become denatured and are subsequently denatured by other proteinases.
Collagenase 1 / MMP-1 / Fibroblast type collagenase
• It is produced by a variety of human epithelial and mesenchymal cells including
keratinocytes,fibroblasts and macrophages.
• It can hydrolyze type I, II, III, VI, VIII and X collagen and gelatin ( Birkedal-Hansen et al
1993).
• It hydrolyzes type III collagen molecules faster when compared to type I.

47. Collagenase 2 / PMN leukocyte collagenase / MMP-8
• It hydrolyzes both type I and type III collagen.It degrades type I faster than
type III collagen.
• It is found only in the specific granules of polymorphonuclear neutrophil cells.
• Gelatinase group of matrix metalloproteinases:
They include
- 72 kd gelatinase A or MMP-2
- 92 kd gelatinase B or MMP-9

48. • Both have a high affinity for gelatin but can also cleave types IV, VII, X and
XI collagens and elastin.
• They cleave the Gly – X peptide bond where X may be
valine,leucine,glutamine or serine.
• Gelatinase B is produced by eosinophils, macrophages, keratinocytes and is
also stored in the polymorphonuclear neutrophil granules.
• Its synthesis is regulated by several inflammatory mediators.
• In contrast gelatinase A synthesis is regulated by TGF-β.

50. FUNCTIONS OF COLLAGEN
• It is the main component of fascia, cartilage, ligaments, tendons, bone
and teeth. It is responsible for skin strength and elasticity, and its
degradation leads to wrinkles that accompany ageing.
• It strengthens blood vessels and plays a role in tissue development
and nutrition.
• It is present in the cornea and lens of the eye in crystalline form

51. • Applications of collagen as a biomaterial
• To repair tissues such as bone, tendon, ligament, skin, vascular and
connective tissues.
• For use as sealant, implant coating, adhesion barrier and tissue
engineering devices.
• Drug delivery applications: to develop scaffolds for delivery of genes,
cell, growth factors, anesthetics, analgesics, antibiotics etc.
• Tissue augmentation: For use in plastic surgery
• For use in collagen coating of grafts.

52. • To enhance blood coagulation and platelet activation
• To enhance durability of allograft tissues
• Can be used for the generation of bone substitutes, wound dressings,
nerve regeneration,
• Artificial skin
• For use as a research tool to study diseases such as diabetes and aging,
and to evaluate drugs

53. • Some of the available Collagen-Based Localised Drug Delivery
Systems
• Collatamp G -Collatamp G is an implantable type-I collagen sponge
impregnated with 2.0 mg/cm2 of gentamicin sulfate. It is approved as
a medicinal drug product in many European countries and is currently
marketed under various brand names. The product is indicated for the
surgical treatment and post-surgical prevention of infection in bone
and soft tissue and has been clinically proven to reduce rates of
infection/reinfection and substantially reduce the average duration of a
hospital stay

54. • INFUSE™ Bone Graft and InductOs™
• Wound healing
• Collagen Stents and Vascular Graft Coatings

55. COLLAGEN MEMBRANES USED IN GUIDED
TISSUE REGENERATION
 The use of devices in periodontal regenerative therapy has been
associated with the concept of guided tissue regeneration. The
hypothesis originated by Melcher and established by Karring et al.
suggests that selected cell populations residing in the periodontium
can produce new cementum, alveolar bone and periodontal ligament,
provided that these populations are given the opportunity to occupy a
periodontal wound.
 Such opportunity arises when other cell populations, such as epithelial
cells or gingival fibroblasts, which also would invade the wound space
are effectively excluded. This provision to exclude specific tissues
during the healing phase of a periodontal defect wound has generated
an impetus for the development of periodontal devices, commonly
called barriers or membranes, for guided tissue regeneration.

56. • Medical Uses
1.Collagen has been widely used in cosmetic surgery, as a healing aid for burn patients, for
reconstruction of bone and a wide variety of dental, orthopedic and surgical purposes.
2. Collagen sponge is also used in filling bone defects.
3. It is also used as a haemostatic agent and as a wound dressing. Eg. Collatape, collacote,
and collaplug.
4. It is used as a slow drug delivery system. For eg. Phosphorylated collagen used in
delivery of epidermal growth factor and DNA- infused gel of modified collagen for the
delivery of cytokines.
5. Injectable collagen has been used in an attempt to correct distensible acne scars, atrophy
from disease or trauma, postrhinoplasty irregularities, glabellar frown lines, nasolabial folds
and variety of other surface depressions and abnormalities.
6.Collagen is also used as a GTR membrane.
7. It is also sold commercially as a joint mobility supplement

57. ASSOCIATED DISEASES
• OSTEOGENESIS IMPERFECTA:
Defective connective tissue,Characterised by impairment of collagen
maturation
↓collagen synthesis or structurally defective collagen.
• Caused by a mutation in type 1 collagen
• dominant autosomal disorder
• results in weak bones and irregular connective tissue
• some cases can be mild while others can be lethal, mild cases have
lowered levels of collagen type 1 while severe cases have structural
defects in collagen

58. • EHLERS DANLOS SYNDROME (Van meekaran -1682)
Group of connective tissue disorder.
Caused by a defect in the structure,production or processing of collagen or
by a defect in the proteins that interact with collagen.
Hyperextensibility of skin,hypermobility of joints and tissue fragility.
Interference with conversion of procollagen to collagen-↓cross linking-
reduction in tensile strength of the tendons.
Hypoplasia,microdontia,pulp stone, deformed roots,subluxation of TMJ
• Ten different types of this disorder, which lead to deformities in connective
tissue. Some types can be lethal, leading to the rupture of arteries. Each
syndrome is caused by a different mutation, for example type four of this
disorder is caused by a mutation in collagen type 3.

59. • STICKLER SYNDROME: (Gunnar stickler -1965)
• It is a group of genetic disorders affecting connective tissue especially
collagen.
• It is thought to arise due to the mutation of several collagen genes
during fetal development.
Premature osteoarthritis,retinal degeneration,hearing loss and
orofacial abnormalities.
Caused due to the mutation in procollagen for type 2 and 11.

60. • ALPORT SYNDROME
 mutation occur on genes of the x –chromosome.
Caused by a defect in type 4 collagen
Renal impairment, hypertension, loss of hearing, haematuria,
proteinuria and lens abnormalities.

61. • SCURVY:
Ascorbic acid (vitamin C) acts as a cofactor in the synthesis of
collagen as it is necessary for hydroxylation of proline and lysine.
Results in defective formation and maintenance of collagen,
impairment or cessation of osteoid formation and impaired
osteoblastic function.
Optimal level of ascorbic acid is apparently required to maintain the
integrity of the periodontal microvasculature.

62. • ROLE IN GINGIVITIS:
Collagenolytic activity is increased in inflamed gingival tissue by the
enzyme collagenase.
Initial lesion-perivascular loss of collagen
Early lesion-increase in the amount of collagen destruction is seen.
Estabilished lesion-collagen fibers are destroyed around the infiltrate
of intact and disrupted plasma cells, neutrophils, lymphocytes,
monocytes and mast cells.

64. • ALTERED COLLAGEN METABOLISM IN DIABETES:
- In addition to defects in collagen production, post translational modifications of
the collagen peptide have also been reported to occur in diabetes.
- Increased cross linking of collagen occurs normally with aging, but it is
accelerated in diabetic skin and tendon and may lead to decreased solubility and
increased accumulation of collagen in tissues throught an increased half life.
- Non enzymatic glycosylation of collagen is also increased in diabetes,which may
affect collagen metabolism by also changing the half life of the collagen peptide.
- It is possible that these post translational modifications of collagen in diabetes
may lead to excess collagen accumulation under conditions where there is
decreased synthesis of collagen.

65. CONCLUSION
• Collagens are fascinating proteins not only because they are unique in structure
and function, but also because of their ubiquitous distribution throughout the
animal kingdom.
• The collagens represent a family of atleast 28 types that have various distribution
patterns and functions in different connective tissues.
• They are synthesized in a complex series of biochemical events and its synthesis is
highly regulated.
• Mechanisms that regulate collagen synthesis have a direct bearing effect on
periodontal structures in which the connective tissue especially collagen undergo
dramatic changes.
• Periodontal regeneration is also intertwined with events associated with collagen
production and degradation.

66. REFERENCES
Bartold PM, Narayanan AS. Biology of the periodontal connective tissues.
Structure, Biosynthesis and Regulation of Collagen. Ch.4; p. 73-92.
Lippincott’s biochemistry:3rd edition;2005;pg 43-48
Orban’s Oral Histology and Embryology
T Ahuja,V Dhakray,M Mittal et al.Role of Collagen in the periodontal
ligament- A Review.The interent journal of Microbiology;10(1):1-7
K. Gelse et al. Collagen-structure,function and biosynthesis.Advanced
Drug Delivery Reviews 2003; 55 : 1531–1546
Spanheimer R,Umpierreez G.Decreased collagen production in diabetic
rats.Diabetes 1988 April;37(4):371-376
Kaur P,Kakar V. Collagen: Role in Oral Tissues: A Review.International
Journal of Science and Research. May 2014;3(5):273-276