JUNCTIONAL EPITHELIUM

Dr.M.SatyaPost graduate

Contents • Introduction • Development of the Junctional epithelium• Structure of the Junctional epithelium• Epithelial attachment apparatus• Turnover of the Junctional epithelial cells• Dynamic aspects of the junctional epithelium• Expression of various molecules and their functions• Junctional epithelium adjacent to oral implants• Regeneration of the Junctional Epithelium• Role of junctional epithelium in the initiation of pocket formation.• Long junctional epihelium

Connective tissue

Epithelium

Gingiva

Gingival Epithelium

The gingival epithelium is similar to epidermis in that it shows a distinct sex difference.

In the female, a large Feulgen-positive particle has been found adjacent to the nuclear membrane ; in the males , a similar but smaller particle is present in 1 to 2 % of the cells.

Marwah, A.S., and wienmann : A sex difference in epithelial cells of human gingiva. J. Periodont,26:11,1955.

Development of Junctional epithelium

According to Gottlieb, the reduced enamel epithelium that covers the crown fuses with the oral epithelium and becomes the Epithelial attachment.

As the tooth erupts, the superficial portion of the attachment progressively separates from the enamel, leaving a cuticle adherent to the tooth surface and forming a V-shaped space- the Gingival sulcus

Epithelial

attachment

Gottlieb

• contended that the gingival sulcus is formed by a split in the Epithelial attachment rather than by separation from the tooth.

Intra epithelial splitWeski, Gross,Euler

and wodehouse

Epithelial cuff

Wearhaug

Epithelial

attachmentGottlieb

Attached

Epithelial cuff

Orban

Junctional

epithelium or attachment

epithelium

Stern

Dento-gingival junction

Schroeder and Listergarten first clarified the anatomy and histology of the dentogingival junction in their monograph-

“Fine structure of developing epithelial attachment of human teeth”

CTJE

Enamel space Internal basal lamina External basal lamina

• Coronally: 15-30 cells thick. Apically: narrows to 1-3 cells

• Length: 0.25 – 1.35mm• Stratified squamous non-keratinized

epithelium that is made up of two strata only i.e., a basal layer(stratum basale) and a suprabasal layer(stratum suprabasale)

Cytokeratins in JE

• JE expresses simple keratin markers such as K8 and K4 which demarcates the SE from JE.

• JE does not express K1 & K10• K19 is present in all layers of JE in monomeric state

which is expressed more in proliferative cell layers• JE attached to tooth through the K5 and 14-

hemidesmosomes assembly• K5,6,7,and 9 are typical of that of simple,rapidly

proliferting,less differentiated epithelia.

?Non-keratinzed

Junctional epithelium

Junctional epithelium is unique as it possess 2 basement membranes – the internal and

external basal lamina

Enamel

Lamina propria

Internal Basal Lamina External Basal LaminaHemidesmosomes

Junctional epithelium

Remarcable permeability

?

Schroeder 1969,1981Schroeder and listgarten 1977

Yamasaki et al 1979Schroeder and Munzel-ppedrazzoli 1970

• The junctional epithelium, particularly its basal cell layers, is well – innervated by sensory nerve fibers

Byers and Holland 1977Kondo et al 1992Maeda et al 1994

Epithelial attachment apparatus

• The attachment of the junctional epithelium to the tooth is mediated through an ultramicroscopic mechanism defined as the epithelial attachment apparatus.

• It consists of hemidesmosomes at the plasma membrane of the cells Directly Attached to Tooth(DAT cells)and a basal lamina-like extracellular matrix, termed the internal basal lamina,on the tooth surface

• The epithelium- tooth interface is a unique structure wherein epithelial cells adhere by means of bonafide hemidesmosomes to an epithelium derived extracellular matrix lacking most of the common BM components. Moreover, TF cells differ from connective tissue facing cells and their production of extracellular matrix, but also by their cytoskeletal architecture.

Marketta Horrnia et al: The dento- epithelial junction:cell adhesion by Type 1 hemidesmosomes in the absence of a true basal lamina. J

Periodontol 2001;72:788-797

DAT cells

• Salonen coined the term DAT cells.(1989)• Innermost suprabasal cells.• They form and maintain the internal basal

lamina that faces the tooth surface

• DAT cells possess stress fibers arranged in parallel to the tooth axis and to the presumable cervical-line in the cytoplasm, and microvilli-like structures on their enamel surfaces.

J Periodontal Res. 2005 Aug;40(4):354-63.Cytoskeleton and surface structures of cells directly attached to the tooth in the rat junctional epithelium.Ishikawa H, Hashimoto S, Tanno M, Ishikawa T, Tanaka T, Shimono M.

The epithelial attachment is not

static but

DYNAMIC

Hemidesmosomes

• a structure representing half of a desmosome, found on the basal surface of some epithelial cells, forming the site of attachment between the basal surface of the cell and the basement membrane.

• Extracellular protiens- laminin-5• Intracellular protiens- plectin and BP

• Hemidesmosomes are transmembrane cell-matrix junctional complexes that are intracellularly connected to the cytoskeleton filaments of epithelial cells

Laminin

Laminin- 511 and 111

Laminin-332

Turnover of the junctional epithelial cells

• The mechanism of DAT cell turnover is not fully understood. Considering the fact that the DAT cells are able to divide and migrate, three possible mechanisms were proposed.

1. The daughter cells produced by dividing DAT cells replace degenerating cells on the tooth surface.

2. The daughter cells enter the exfoliation pathway and gradually migrate coronally between basal cells and the DAT cells to eventually break off into the sulcus, or

3. Epithelial cells move/migrate in the coronal direction along the tooth surface and are replaced by basal cells migrating round the apical termination of the junctional epithelium

• At the coronal part of the JE, the DAT cells typically express a high density of transferrin receptors,which supports the idea of their active metabolism and high turnover

Junctional epithelium in the antimicrobial defense

JE consists of active population of cells and antimicrobial functions which together form the 1st line of defense against microbial invasion into tissue

• Several antimicrobial mechanisms exist in the junctional epithelium.

• In the coronal part of the junctional epithelium quick cell exfoliation (1) because of rapid cell division (2) and funnelling of junctional epithelial cells towards the sulcus hinder bacterial colonization. Laterally, the (external) basement membrane forms an effective barrier against invading microbes (3). Active antimicrobial substances are produced in junctional epithelial cells. These include defensins and lysosomal enzymes (4). Epithelial cells activated by microbial substances secrete chemokines, e.g. interleukin- 8 and cytokines, e.g. interleukins -1 and -6, and tumour necrosis factor-a that attract and activate professional defense cells, such as lymphocytes (LC) and polymorphonuclear leukocytes (PMN). Their secreted product, in turn, cause further activation of the junctional epithelial cells (5).

Junctional epithelium adjacent to oral implants

Regeneration of the junctional epithelium

Location and functions of molecular factors associated with the junctional

epithelium

The detachment of the DAT cells from the tooth surface

• The GCF passing through the junctional epithelium determines the environmental conditions and provides sufficient nutrients for the DAT cells to grow. At the gingival margin the GCF may become contaminated so that agents from the oral cavity and/or the plaque bacteria challenge the most coronal DAT cells.

• Obviously ,the conditions for DAT cell survival and adequate function at the coronal part of the JE are different and more susceptible of compromises than those for the basal cells living in the vicinity of the connective tissue(CT) and the blood circulation.

Role of the GCF

Bacterial agents -endotoxins,hydrogen sulfide, butyric and propionic acids.bacterial collagenases and variety of enzymes,such as hyaluronidases and neuraminidases.

Host derived agents - complement factors,prostaglandins, different cytokines, intracellular enzymes, and products of tissue breakdown such as lactate dehydrogenase, aspartate aminotranfearases and collagen peptides.

Antimicrobial agents and leukocyte-derived enzymes such as lysozyme, alkaline phosphatase,β-glucoronidase, cathepsin D, elastin ,collagenase and lactoferrin.

The degeneration and detachment of DAT cells exposes the tooth surface

and creates a subgingival niche suitable for the colonization of

anareobic gram –ve bacteria and apical growth of dental plaque

Primary granules/azu

rophilic granules

•Myeloperoxidase•Elastase•Lysozyme•Cathepsin G•Urokinase•Acid hydrolases and•defensins

Secondary

granules

•Lactoferrin•Elastase•lysozyme

Role of the PMN’s

lactoferrin

• It has high affinity for iron and it acts on bacteria by causing iron depletion, and thus reduction in bacterial cell division rate, glucose metabolism and macromaolecular synthesis

health disease

600μg/ml 1500μg/ml

High conc of lactoferrin hamper epithelial cell growth by interfering with their adhesion and spreading .The molecule may have a role in delaying the repair of the JE/DAT cell population during severe inflamation.

• Collagenases, stromelysins,gelatinases• Plasminogen activator• Cathepsin• elastase

Role of host proteinases and inflammatory mediators

Role of bacterial products

GingipainsDisturbs the ICAM-1-dependent adhhesion of PMNs.

Tada et al 2003

• Short chai fatty acids• Hydrogen sulfide• ammonia

The protien rich, short chain fatty acid containing and annaerobic conditions in the sub-gingival space,HS appaers to be a potential candidate to cause significant damage to

JE/DAT cells.

Role of risk factors for periodontal disease

LONG JUNCTIONAL EPITHELIUM

Thank you

A functional epithelial seal must be re-established at the most coronal portion of the tissues and be no more than 2 mm in length.

• The long junctional epithelium is formed by the keratinocytes of the oral epithelium repopulating the wound and migrating over the root surface.

• Fragments of fibronectin are thought to be chemotactic to various periodontal subtypes and are thought to play an important role in the formation of Long Junctional Epithelium

• The formation and organization of the wound clot over the root surface is a property of the fibronectin molecules that are expressed in the early phases of wound healing.

• The oral keratinocytes express integrins such as α5β1 that are normally present in the epithelium when they come into contact with fibronectin.

• These integrins promote the migration of these keratinocytes over the root surface and form the long junctional epithelium.

Removal of junctional and pocket epithelium

curettage Chemical agents

Surgical techniques

Glickman and Prichard have advocated performing a gingivectomy to the crest of the alveolar bone and debriding the defect

The Modified Widman flap

Ramfjord and Nissle

Prevention or impeding of Epithelial Migration

• Elimination of junctional or pocket epithelium may not be sufficient

because

1st approach

RST

2nd approach

CORONALLY DISPLACED FLAPS

GUIDED TISSUE REGENERATION

REFERENCES

• Clinical periodontology- IRVING GLICKMAN : 3rd edition

• ORBAN,s Oral histology and Embryology- 11th edition• CLINICAL PERIODONTOLOGY –CARRANZA’S- 10TH EDITION

• D.D. Bosshardt and N.P. lang :The junctional epithelium: from health to Disease :J Dent Res(1):9-20,2005.

• Marja T,Jukka I.Salonen:structure and function of the tooth- epithelial interface in health and disease.

• Periodontology 2000,vol 31,2003.

Thank you