Collagen is most abundant protein in mammals, the main fibrous component of skin, bone, tendon and cartilage.
Collagen comprises one- third of the total protein, accounts for three-quarters of the dry weight of skin, and is the most prevalent component of the extracellular matrix.
The collagen family consists of 28 members and these are classified by Roman numbers on the basis of their chronology of discovery.
intracellularly within the lysosomal apparatus of fibroblasts after the phagocytosis of redundant collagen fibrils. recognition of redundant collagen fibrils , by integrins Partial enclosure and digestion of the fibril by MMPs Formation of phagolysosome digestive lysosome Final digestion of the enclosed collagen fibrils by cysteine proteinases 2. Extra cellular major tissue remodeling involving large amounts of collagen breakdown and during inflammation. . The matrix is maintained by a careful balance between rate of synthesis, degradation and connective tissue cell division, but imbalance between activated MMPs and their endogenous inhibitors leads to pathologic breakdown of extracellular matrix during periodontitis. . The matrix is maintained by a careful balance between rate of synthesis, degradation and connective tissue cell division,
Cultured skin substitutes developed on collagen lattices as a support for epithelial growth 2. controlled release of drug
This leads to a restricted mouth opening, resulting in trismus leading to restriction of food consumption, difficulty in maintaining oral health, as well as impairs the ability to speak.
Collagen and collagen disorders
Dr. Achi joshi
Dept Of Periodontics
Biosynthesis of collagen
Types and functions of collagen
Degradation and remodelling of collagen
Collagen in periodontal tissue
Collagen is most abundant protein in mammals and accounts for 25-30% of their
Collagen is the main fibrous component of skin, bone, tendon and cartilage.
Collagen comprises one- third of the total protein, accounts for three-quarters of
the dry weight of skin, and is the most prevalent component of the extracellular
The word collagen comes from the Greek word,
“kola,” meaning, “Glue producing”
French word, collagene designates glue-producing constraints because collagenous
tissue were used as source of glue and gelatin.
When it is heated in water, it gradually breaks down to produce soluble derived
protein i.e. gelatin or animal glue.
Miller and Matukas discovered collagen in 1969, since then 26 new collagen types
have been found.
The collagen molecule is a rigid rod like structure that resists stretching.
Therefore this protein is an important structural component in tissues such as the
periodontal ligament, muscles and tendons in which the mechanical forces need to be
Collagen can also influence cell shape, differentiation and many other cellular
activities. Thus, forming an important group of multifunctional connective tissue
protein that participates in many biological functions.
All collagens are composed of 3 polypeptide alpha chains coiled
around each other to form the tripe helix configuration.
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 a continuous stretch or it may be
interrupted by non collagenous elements.
There are around 3 amino acids per turn.
The triple-helical sequences are comprised of Gly-X-Y
repeats, X and Y being frequently proline and 4-hydroxy-
Glycine occupies every third position in the repeating
amino acid sequence, it is essential for the triple helical
conformation because larger amino acids will not fit in the
center of the triple helix. 8
In the α chain of type I collagen there are 338 Gly – X – Y triplets repeated in a
sequence and additional 32 amino acids flank the long triplet sequence at each
end. They are known as telopeptides. There is both an amino terminal ( -NH2 )
and a carboxy terminal (-COOH ) telopeptide.
Proline and hydroxyproline in the α chains are imino acids with a rigid cyclical
Stabilization of the triple helix is by-
the presence of glycine as every third residue,
a high content of proline and hydroxyproline,
inter-chain hydrogen bonds, and
electrostatic interactions involving lysine and aspartate.
Collagen biosynthesis, starting with transcription of genes within nucleus to aggregation of
collagen heterotrimers into large fibrils is a complex multistep process.
The entire process of collagen biosynthesis-
Translational and post translational events or intracellular steps in collagen synthesis
Extracellular collagen biosynthetic events
Regulation of synthesis
There are more than 40 genes described for collagen types I to XXVIII.
Collagen is a structural protein and its synthesis is similar to synthesis of any
other protein molecule and involves process of transcription and translation of
From collagen genes mRNA for each collagen type is transcribed, it undergoes
many processing steps to produce a final code for that specific collagen type. This
step is called mRNA processing.
The initial RNA transcript is processed to mRNA and it gives rise to the primary 12
The polypeptide chain formed initially is a helical molecule with two non-helical
extensions one at the NH2 and the other at the –COOH terminal end (telopeptide)
The –NH2 terminal extension has a leader or signal sequence that directs the
entry of the molecule into the rough endoplasmic reticulum.
The pre- pro-collagen molecule is converted to pro collagen molecule by removal of
signal peptide by signal peptidase and undergoes multiple steps of post-
Hydroxyproline and hydroxylysine are formed in the RER by the hydroxylation of
prolyl and lysyl residues. This is an essential step in biosynthesis of collagen for it
stabilises the molecules.
Requirements for hydroxylation are: Specific enzymes-
prolyl hydroxylase and lysyl hydroxylase
Ascorbic acid (Vitamin C)
The enzyme galactosyl transferase catalyzes the addition of galactose to a
hydroxylysyl residue .
Glucosyl transferase catalyzes the further addition of glucose.
Formation of procollagen
Following hydroxylation and glycosylation, three polypeptide chains form a triple
Secretion of procollagen
Procollagen passes into the Golgi complex before its secretion into the interstitial
In the interstitial spaces,
Procollagen amino-peptidase and procollagen carboxylase catalyze the removal of
the two peptide chains that form the extension of the procollagen molecule.
Cross-linkage of fibrils to form fibres
There is oxidative deamination of specific lysyl or hydroxylysyl residues to form
aldehydes; the reaction is catalyzed by lysyl oxidase.
The collagen family consists of 28 members and these are classified by Roman
numbers on the basis of their chronology of discovery.
Variations are brought by
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.
I Provides tensile strength to connective tissue
II Provides tensile strength to connective tissue
III Forms structural framework of spleen, liver, lymph nodes, smooth muscle,
adipose tissue. Provides tensile strength to connective tissue
IV Forms meshwork of the lamina densa of the basal lamina to provide support
V Provides tensile strength, associated with type I collagen, also with
placental ground substance.
VI Bridging between cells and matrix (has binding properties
for cells, proteoglycan, a type I collagen)
VII Forms anchoring fibrils that fasten lamina densa to
underlying lamina reticularis
VIII Tissue support, porous meshwork, provide compressive
IX Associates with type II collagen fibers
X Calcium binding
XI Provides tensile strength, controlling lateral growth of type II fibrils
XII Associated with type I collagen fibers
XIII Cell matrix and cell adhesion
XIV Modulates fibril interactions
XV Proteolytic release of antiangiogenic factor
XVII Cell to matrix attachment
XVIII Proteolytic release of antiangiogenic factor
XIX formation of hippocampal synapses
XXIV Regulation of type I fibrillogenesis, marker of osteoblast
differentiation and bone formation
XXVII cartilage calciﬁcation, Association with type II fibrils (?)
Extracellular matrix remodeling requires the degradation of its components. In
general, four types of proteolytic enzymes, capable of ECM degradation, exist:
Matrix metalloproteinases (MMPs)
Serine proteinases (e.g. plasmin)
Cysteine proteinases (e.g. cathepsin K) and
The MMPs are considered to be essential for the degradation .
The collagenases are responsible for the first degradation step of collagen, in
which the fibers are cleaved into the characteristic 1/4 and 3/4 fragments.
Gelatinases and cysteine proteases further degrade the collagen fragments.
Collagen degradation is an essential component of tissue development during
growth and of tissue maintenance in the adult.
Collagenases are widely distributed in the tissues and they bring about collagen
turnover, which is under physiological control, and can bring about pathological
destruction of connective tissue or provoke excessive new collagen deposition and
Imbalance between activated MMPs and their endogenous inhibitors leads to
pathologic breakdown of extracellular matrix during periodontitis.
Collagen is regarded as one of the most useful biomaterials.
The excellent biocompatibility and safety due to its biological characteristics, such
To repair tissues such as bone, tendon, ligament, skin, vascular and connective tissues.
Drug delivery applications: to develop scaffolds for delivery of genes, cell, growth
factors, anesthetics, analgesics, antibiotics etc.
For LDD in periodontal pockets
Tissue augmentation: For use in plastic surgery
To enhance blood coagulation and platelet activation
To enhance durability of allograft tissues.
In guided tissue regeneration.
Can be used for the generation of bone substitutes, wound dressings, nerve
For use as a research tool to study diseases such as diabetes, aging and to
Available in abundance and easily puriﬁed from living organisms (constitutes
more than 30% of vertebrate tissues)
Biodegradable and bio-reabsorbable.
Non-toxic and biocompatible.
Biological plastic due to high tensile strength and minimal expressibility.
Hemostatic — promotes blood coagulation.
Formulated in a number of different forms.
Biodegradability can be regulated by cross-linking.
Easily modiﬁable to produce materials as desired by utilizing its functional
Compatible with synthetic polymers.
High cost of pure type I collagen.
Variability of isolated collagen (e.g. crosslink density, ﬁber size, trace impurities, etc.)
Hydrophilicity which leads to swelling and more rapid release.
Variability in enzymatic degradation rate as compared with hydrolytic degradation.
Complex handling properties.
Side effects, such as bovine spongeform encephalopathy (BSF) and mineralization.
The collagen of periodontium 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.
Out of 22 to 25% of organic component 94 to 98% is mainly collagen type I.
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.
Predominant collagen present in cementum is type I
collagen (forms 90% of the organic matrix).
Other collagens associated with cementum include type
III, a less cross-linked collagen found in high
concentrations during development, repair, and
regeneration of mineralized tissues and type XII that binds
to type I collagen and to non-collagenous matrix proteins.
Collagens found in trace amount in cementum are types V,
VI and XIV.
Collagens are the most abundant biochemical constituents of gingival connective
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-
5.Circular and semicircular
Periodontal ligament is composed of collagen fibers
bundles connecting cementum and alveolar bone proper.
The vast majority of collagen fibrils in the periodontal
ligament are arranged in definite and distinct fiber
bundles and these are termed as principal fibers.
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 di-hydroxy-lysine while hydroxyl-lysine is a minor component
The presence of covalent cross-links between collagen molecules stabilizes the
ligament fibres and increases the tensile strength
Majority of PDL collagen fibers are arranged in to
Horizontal & Oblique directed groups to adapt to axial
The complex 3D arrangement of fibers means that some
bundles would always be placed in Tension, irrespective
of the direction of an applied force. This enables local
areas of the PDL to resist compressive forces
Tooth support system is a multiphasic system comprising of
fibres , ground substances, blood vessels, fluids acting together
to resist mechanical forces.
Internal Orientation of collagen fibers influences the
mechanical properties of the tissue . Collagen fibers best resist
axially directed force as majority of PDL collagen fibers are
arranged in to Horizontal & Oblique direction.
OVERLAPPING ARRANGEMENT of fibers as visible in Electron Microscope
looks like the spokes of a cycle wheel.
This is very crucial in withstanding Rotational & Intrusive Forces.
This overlapping arrangement helps in spreading the load uniformly and reduce
the strain on PDL.
The terminal ends of the collagenous principal fibers
are inserted in to bones to form Sharpey’s Fibers.
These 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
Collagenous tissues exhibit a quantifiable periodicity of structure of variable scale,
the waveform that describes this periodicity has been referred to as crimp.
In the polarizing microscope crimping can be seen by regular banding of dark lines
across the bundles.
Sharp Zig-Zag arrangement of collagen fibers with quantifiable periodicity angular
deflection from axis
Microanatomical organization of collagenous sheets and bundles in sinusoidal wave forms.
It is an early ,easily extensible , non linear region that causes the straightening out of
the crimp, this enables the ligament to absorb impact tensile loads without extending
collagen fibrils and without producing heat.
Fibroblast processes in the developing collagenous tissues play a role in fabricating the
crimped arrangement and consequently that crimping may be an important feature in
It also has been proposed that crimp some times can generate contractile forces in
Collagenolytic activity is increased in inflamed gingival tissue by the enzyme collagenase. Following
changes are seen in three different stages of 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.
This is necessary so that tissues can be pushed apart to accommodate the infiltrating cells and it is
considered to be a space creating process.
The main fiber groups affected appear to be circular and dentogingival fiber assemblies.
In established lesion – collagen fibers are destroyed around the infiltrate
of intact and disrupted plasma cells, neutrophils, lymphocytes, monocytes and
Collagen loss continues in both lateral and apical directions as the inflammatory
cell infiltrate expands resulting in collagen depleted spaces extending deeper into
the tissues which are then available for leukocyte infiltration.
In periodontal pockets
Apical to the junctional epithelium, collagen fibers are destroyed and the area becomes
occupied by inflammatory cells and edema.
As the consequence of the loss of collagen,the apical cells of the junctional epithelium
proliferate along the root, extending finger like projections two or three cells in thickness.
1. Drug delivery- For LDD in periodontal pockets
The key benefit of localised drug delivery over systemic therapy is that high
concentrations of drug can be maintained at the target site, while avoiding risk of
systemic toxicity and associated side-effects.
The drugs can be loaded into collagen membranes by hydrogen bonding, covalent
bonding or simple entrapment.
PPAB is collagen fibril based formulation containing
tetracycline hydrochloride (2 mg of tetracycline) in 25 mg
of collagen fibrils.
Sterile collagen Fibres with Tetracycline Hydrochloride for
2. Tissue augmentation- recession coverage
Collagen membranes are used as an alternative to connective tissue grafts in
It shows similar histologic and clinical outcomes, achieving complete root coverage
when compared with connective tissue grafts.
It gets completely incorporated in the adjacent host connective tissues without
any signs of inﬂammation.
3. 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.
Demineralized bone collagen is used as a bone graft material for the treatment of
acquired and congenital bone defects either by itself or in combination with
Osseograft/DMBM is one such de-mineralized bone
derived Type-I collagen for bone void filling
Dembone is Demineralized Freeze-dried Cortical Bone
Powder, prepared from cortical bone harvested from
carefully screened human donors, demineralized in HCl
acid, freeze dried and triple sterilized before vacuum
Sterile Synthetic Nanocrystalline Hydroxyapatite Bone Graft.
particle size ranging from 200-300 and 600-700 microns.
4. In guided tissue regeneration- GTR membranes
Guided tissue regeneration (GTR) is a procedure that attempts to reconstitute the lost tissues
and is based on the concept of selective repopulation.
The first report of a human tooth treated by guided tissue regeneration was by Nyman et al in
1982, with the term GTR coined by Gottlow et al in 1986.
To exclude the fast-growing cells of the gingival epithelium from migrating to the wound, GTR
procedures use barrier devices that are placed between the periodontal flap and the osseous
defect to maintain a space for repopulation of the defect with cells having regenerative
thin sheet made of high purity Type-I collagen derived
from selected animal tissues. Periocol® / Helisorb®-GTR
Type 1 collagen membrane of fish origin for GTR applications
During the healthy process of blood clotting, platelets become activated by thrombin
and aggregate at the site of injury.
Stimulated by the protein fibrinogen, the platelets then clump by binding to the
collagen that becomes exposed following rupture of the endothelial lining of blood
Collagen is therefore a natural haemostat and a wide variety of collagen-based products
are used in surgery and dentistry to control excessive bleeding or haemorrhage.
Absorbable sterile fibrillar collagen wound filler, constituted
using high purity type-1 reconstituted collagen
•Control bleeding and stabilizes blood clots
•Protects wound bed
Sterile Absorbable Haemostatic Gelatin Sponges
Collagen diseases may be genetic, auto-immune or miscellaneous like defects due
to nutritional deficiencies, drug induced defects etc. An inborn error of metabolism
involving abnormal structure or metabolism of collagen results in collagen
disorders. All these affect the biosynthesis, assembly, post-translational
modification, secretion, or other processes involved in normal collagen production.
Heritable collagen disorders are caused by mutations in the genes coding for
collagen α chain.
The mutations affect the extracellular matrix by decreasing the amount of
secreted collagen, impairing molecular and supra-molecular assembly through the
secretion of a mutant collagen, or by inducing endoplasmic reticulum stress and
the unfolded protein response.
The disease is characterized by-
extremely fragile bones
reduced bone mass
hearing loss and
This is due to mutations in one of the two genes, COL1A1 and COL1A2, which
encode the two chains of type I collagen, the major protein of bone.
The most common mutations of this disease is due to substitution of glycine with a
bigger amino acid.
Heterogeneous group of heritable disorders of connective tissue characterized by –
skin hyperextensibility, and
tissue fragility affecting skin, ligaments, joints, blood vessels, and internal organs.
Cause- mutations in the COL5A1 and COL5A2 genes encoding the α1 and α2 chains
of type V are defined.
Early onset generalized periodontitis resulting in the premature loss of deciduous
and permanent teeth.
The gingiva is fragile and hemorrhage may be difficult to control during surgical
Absence of the inferior labial and lingual frenula has been reported in EDS II,
EDS III and suggested to be a highly speciﬁc and sensitive marker for these
Alport syndrome is a progressive hereditary nephritis with Extra-
renal complications, like sensory-neural hearing loss and ocular
Caused by deletion mutations in COL4A5 and COL4A6 genes or
COL4A3 and COL4A4 genes encoding the α3 (IV) and α4 (IV) chains.
This syndrome affects some of the basal membranes and is
characterized by renal failure, loss of hearing and lens abnormalities.
Epidermolysis bullosa (EB) is a clinically and genetically heterogeneous group of inherited
disorders that are characterized by blistering of the skin and certain other tissues.
mutations in COL7A1, affecting the structure of type VII collagen.
Type VII collagen forms delicate fibrils that anchor the basal lamina to collagen fibrils in
These anchoring fibrils are reduced in this form of the disease, causing friction and
A rare, inherited disorders of skeletal development and linear growth.
Involve disturbances of the cartilage components of the growing skeleton, it is
Mutations of the gene for type II collagen, COL2A1, produce a broad spectrum of
clinical phenotypes that fall under the general designation, spondyloepiphyseal
Knobloch syndrome is an autosomal recessive disorder
characterized by high myopia, vitreo-retinal degeneration,
occipital bone damage, and congenital encephalocele.
pathological mutations in the COL18A1 gene at 21q22.3
have been identified.
These mutations cause the loss of one or all collagen
COL18A1 isoforms or endostatin.
Bethlem myopathy is an autosomal
dominant inherited relatively mild
disease that is characterized by muscle
weakness and distal joint contractures.
Type VII collagen plays a role in
connecting cells and extracellular matrix
and that mutations in genes encoding
collagen VII result in Bethlem myopathy.
It is a unique autosomal dominant
syndrome of premature osteoarthritis,
retinal degeneration, hearing loss and
caused by mutations in the COL2A1,
COL11A1 and COL11A2 procollagen genes
of type 2 and 1 collagen.
This autosomal dominant disorder
usually presents after the age of 2–3
years with mild short stature, bowing
of the lower extremities, and a
Osteolathyrism is a collagen cross-linking deficiency caused by dietary
over-reliance on the seeds of Lathyrus sativus (kesari dal) in some
parts of India.
Osteolathyrogenic compounds like Beta-aminopropionitrile (BAPN) and
Beta-oxalyl aminoalanine [BOAA] found in Kesari dhal inhibit enzyme
lysyl oxidase required for the formation of cross links in the triple
weakness and fragility of skin, bones, and blood vessels
Paralysis of the lower extremities associated with neurolathyrism
Collagen diseases share similarities with autoimmune diseases, because
autoantibodies specific to each collagen disease are produced.
Multiple organs may be affected.
Lupus erythematosus is a multifactorial
autoimmune collagen vascular or connective
tissue disease, which may affect the oral
mucosa in either its cutaneous and systemic
forms with varied prevalence
Oral lesions include ulceration, pain,
erythema and hyperkeratosis. Other oral
complaints are xerostomia, stomatodynia,
candidiasis, periodontal disease and
This disease is considered to be a consequence of
disturbances in the homeostatic equilibrium between
synthesis and degradation of extracellular matrix, wherein
collagen forms a major component, thus can be recognized
as a collagen-metabolic disorder.
It is characterized by a juxta epithelial inflammatory
reaction followed by fibroelastic change in the lamina
propria and associated epithelial atrophy.
Key function of ascorbic acid is its involvement in the synthesis of collagen fibers from
proline via hydroxyproline.
Other metabolic reactions for which vitamin C is required are the hydroxylation of
lysine into hydroxylysine in collagen.
In individuals who suffer from a deficiency of this vitamin, the α-chains of the
tropocollagen molecules are unable to form stable helices and the tropocollagen
molecules are incapable of aggregating into fibrils.
Avitaminosis C is associated with the failure
of wound healing or the rupture of
capillaries due to intrinsic intercellular
weakness with lack of connective tissue
support of the capillary walls.
Oral manifestations –
Fetid odor and loosened teeth,
gingivae are boggy, ulcerated and bleed
interdental and marginal gingiva become
bright red, smooth, swollen and shiny.
In the hyperglycemic state, numerous proteins and matrix molecules undergo a
non-enzymatic glycosylation, resulting in accumulated glycation end products
Collagen is cross-linked by AGE formation, making it less soluble and less likely
to be normally repaired or replaced.
As a result, collagen in the tissues of patients with poorly controlled diabetes is
aged and more susceptible to breakdown i.e., less resistant to destruction by
1. Hereditary gingival fibromatosis
both dominant autosomal inheritance and recessive autosomal inheritance
It is a gradually progressive benign enlargement that affects the marginal,
attached, and interdental gingiva.
Histopathologically, it implies an increase in both extracellular matrix and cell
2. drug induced enlargement
Fibroblasts become sensitive to phenytoin, and this results in subsequent
increased production of collagen.
The enzyme collagenase secreted by phenytoin-sensitive fibroblasts is relatively
inactive to degrade collagen.
An imbalance in production and degradation results in the over accumulation of
collagen and hence in an increase in the bulk of connective tissue.
B. Calcium channel blockers
After an interaction between nifedipine and gingival fibroblasts, overproduction of
collagen and extracellular ground substance occurs and leads to an increase in the
size of the gingiva.
C. Cyclosporin induced
It was found that CsA could react with a phenotypically distinct subpopulation of
gingival fibroblasts to enhance protein synthesis.
Collagens have ubiquitous distribution throughout the animal kingdom. Collagens
serve important mechanical functions within the body, particularly in connective
tissues and also exert important functions in the cellular microenvironment.
It is an important constituent of periodontium therefore knowledge of the structure,
biosynthesis and interactions of collagen with other components, its regulation and
degradation mechanisms and changes it undergoes with age and diseased state is
essential, for the understanding of the functioning of the periodontium.