Dermo epidermal junction


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Dermo epidermal junction

  1. 1. D ermo – E pidermal J unction Presented by Adel A. Al-Ghamdi Dermatology Department King Fahd Hospital of university
  2. 2. <ul><li>Introduction </li></ul><ul><ul><li>Origin of basement membrane </li></ul></ul><ul><ul><li>Function of basement membrane </li></ul></ul><ul><li>Ultrastructure of DEJ </li></ul><ul><li>Ubiquitous components of basement membrane </li></ul><ul><li>epithelial-specific basement membrane components </li></ul><ul><li>Scope in some diseases affecting DEJ </li></ul>
  3. 3. Introduction
  4. 4. <ul><li>It is a highly complex form of basement membrane which underlie epithelial & endothelial cells which separate them from each other or from the adjacent connective tissue stroma. </li></ul><ul><li>It is considered as one of the largest epithelial-mesenchymal junction on the body. </li></ul><ul><li>It forms an extensive interface between the dermis & epidermis. </li></ul><ul><li>It is continuous with the junction between dermis & epidermal appendages. </li></ul>
  5. 5. <ul><li>As all basement membranes, it stains strongly for carbohydrates & anionic sites </li></ul><ul><ul><ul><ul><ul><li>Periodic acid shifft stain (PAS) </li></ul></ul></ul></ul></ul><ul><li>The complexity & heterogeneity of DEJ can be appreciated only at electron microscopic level </li></ul>
  6. 6. Origin of Basement Membrane <ul><li>Serial studies strongly suggest that all types of basement membranes are not produced by a single cell type, but rather it is contributed to by both epithelial & mesenchymal cells. </li></ul><ul><ul><li>Laminine 5 & 6 epidermal compartment </li></ul></ul><ul><ul><li>Nidogen mesenchymal compartment </li></ul></ul><ul><ul><li>Type IV collagen & other laminines produced by both compartment </li></ul></ul>
  7. 7. Functions of basement membrane <ul><li>Substrates for the attachment of differentiated cells </li></ul><ul><li>Templates for repair and restoration of tissue functions. </li></ul><ul><li>Sites of attachment for different cell layers or for cells to their underlying matrix. </li></ul><ul><li>Substrates for the programmed migration and selective interactions of germ layers in development. </li></ul><ul><li>Barriers to cell passage in normal tissues. </li></ul><ul><li>Protection of attached cell types from apoptosis. </li></ul><ul><li>The anchoring complex within the epithelial basement membrane is responsible for the stability of epithelial-stromal attachment. </li></ul>
  8. 8. Ultrastructure of DEJ
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  10. 10. Ultrastructure of DEJ <ul><li>Each of these zones contains structures that are distinctive by ultrastructure, biochemical & immunological criteria. </li></ul><ul><li>Size of these regions varies in different tissue types, at different ages & as consequence of several disease states. </li></ul>DEJ 1 ST ZONE 2 ND ZONE 3 RD ZONE Sub basal lamina Lamina densa Tonofilement, Hemidesmosomes Anchoring filement complexs
  11. 11. First zone <ul><li>Tonofilament – Hemidesmosome- Anchoring filaments Complex. </li></ul><ul><li>It is the site of attachment of the epithelium to the basement membrane. </li></ul><ul><li>Tonofilaments </li></ul><ul><ul><li>Also called keratin intermediate filaments, it is comprising keratin 5&14. </li></ul></ul><ul><ul><li>It is a fine filamentous structures maintain the intracellular architecture & organization of basal cells. </li></ul></ul><ul><ul><li>They course through the basal cells & inserted into the desmosome & hemidesmosome. </li></ul></ul>
  12. 12. <ul><li>Hemidesmosome </li></ul><ul><ul><li>Numerous electron- dense plated located in the region of the plasma membrane of the basal cells. </li></ul></ul><ul><li>Lamina Lucida </li></ul><ul><ul><li>External to the plasma membrane </li></ul></ul><ul><ul><li>25- 50 nm in width. </li></ul></ul><ul><ul><li>Contains the anchoring filaments </li></ul></ul>
  13. 13. Second zone <ul><li>Lamina densa </li></ul><ul><ul><li>Appears as an electron- dense amorphous structure. </li></ul></ul><ul><ul><li>20-50 nm in width below it the dermal epidermal basal lamina. </li></ul></ul><ul><ul><li>At high magnification, it has a granular fibrous appearance. </li></ul></ul><ul><ul><li>Account for 40 -65% of total basement membrane proteins. </li></ul></ul><ul><ul><li>Major proteins component is type IV collagen where it appears as a filament of variable thickness which is morphologically distinct from the collagen fibers in the subjacent dermis. </li></ul></ul>
  14. 14. <ul><ul><li>The basement membrane heparin sulfate proteoglycan appears as sets of two parallel lines of the surface of the collage cords. </li></ul></ul><ul><ul><li>Laminin also associated with the cords, appearing as a fine wavy lines. </li></ul></ul>
  15. 15. Third zone ( the sub basal lamina) <ul><li>It contains several microfibrillar structures in which 3 of them can be distinguished. </li></ul><ul><li>Anchoring fibrils </li></ul><ul><ul><li>It appears as condensed fibrous aggregates 20 - 75 nm in diameter ( not found in the basement membrane of blood vessels ,smooth muscles). </li></ul></ul><ul><ul><li>At high resolution, these structures appear to have a nonperiodic cross-striated banding pattern (positively stained of collagen). </li></ul></ul>
  16. 16. <ul><ul><li>The anchoring fibrils are primarily aggregates of type VII collagen. </li></ul></ul><ul><ul><li>The proximal end inserts into the basal lamina, & the distal end is integrated into the fibrous network of the dermis. </li></ul></ul><ul><ul><li>Many of the anchoring fibrils inserted their distal ends into electron-dense amorphous-appearing structures completely independent of lamina densa, known anchoring plaques . ( type IV collagen primarily ) </li></ul></ul>
  17. 17. <ul><li>The other 2 types of tubular microfibrils where on the bases of classic histochemical staining procedures, these have been identified as elastic – related fibrils . </li></ul><ul><ul><li>The microfibrillar component in the absence of amorphous component known as Oxytalan fibers. </li></ul></ul><ul><ul><li>The microfibrillar component in the presence of small amounts of amorphous component known as Elaunin fibers, and in the presence of abundant amorphous component known as Elastic fibers. </li></ul></ul>
  18. 18. <ul><ul><li>In the papillary dermis, oxytalan fibers insert into the basal lamina perpendicular to the basement membrane & extend into the dermis, where they merge with elaunin fibers to form a plexus parallel to the axis of DEJ, where they appear to be continuous with elastic fibers present deep within the reticular dermis. </li></ul></ul><ul><ul><li>From this distribution of this structure, we can appreciate that DEJ provides a continuous series of attachment among the major connecting tissue component of the reticular dermis & internal cytoskeletons of the basal cells. </li></ul></ul>
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  20. 20. Ubiquitous Components of Basement Membrane Type IV collage Laminin Nidogen/Entactin Heparan sulfate proteoglycan
  21. 21. Type IV Collagen <ul><li>Immunolocalized mainly to L.D. & also found in anchoring plaque. </li></ul><ul><li>It has a structure closely related to the intracellular or procollagen form, typical of all members of the collagen protein family. </li></ul><ul><li>All procollagens contain 3 subunit peptides, termed alpha chains. </li></ul><ul><li>Several collagens are homopolymers of 3 identical chains ( i.e. type II, III,VII) , although some are hetropolymers containing 2 identical chains & one dissimilar alpha chain. ( i.e. type I, IV,V) </li></ul>
  22. 22. <ul><li>The largest portion of all procollagen molecules is composed of a characteristic triple-helical domain. </li></ul><ul><li>The stability of this structural domain depend upon:- </li></ul><ul><li>The presence of the amino acid glycine in every 3 rd position of the amino acid sequence of each chain. </li></ul><ul><li>A high content of the amino acid proline. </li></ul><ul><li>Post translational hydroxylation of specific proline residues to hydroxyproline. </li></ul>
  23. 23. <ul><li>In the content that these criteria are met, the resulting triple-helix structural domain are:- </li></ul><ul><ul><li>Resistant to non-collagen-specific protease digestion. </li></ul></ul><ul><ul><li>Has extended, semirigid conformation. </li></ul></ul><ul><li>Type IV collagen contain both triple-helical & globular domain. </li></ul><ul><li>The amino terminus of type IV procollagen (NC-I) is globular, similar to the analogous structure of other procollagens. </li></ul>
  24. 24. <ul><li>The carboxyl-terminal domain appears to contain a short globular region ( NC-2) preceded by a relatively large second triple helical domain. </li></ul><ul><li>The triple helical nature of the amino terminus of type IV collagen is unique & has been designated as the 7-S domain. </li></ul><ul><li>Covalent interactions among 7-S domain of the type IV collagen are the basis for the specialized fiber form characteristic of basement membrane. </li></ul><ul><li>The major triple helix of type IV collagen measures 330 nm, which is longer than other types of collagens ( types I,II,III,V = 300nm). </li></ul>
  25. 25. <ul><li>It is not helical throughout its length but contains several specific sites at which glycin is not present in every 3 rd position. </li></ul><ul><li>These minor discontinuities in the triple-helical structure result in increased flexibility in the type IV collagen helix & increased its resistance to a variety of proteases. </li></ul>
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  28. 29. Laminin <ul><li>Immunolocalized to L.D. </li></ul><ul><li>It is a member of glycoprotein family with semirigid & extended structures. </li></ul><ul><li>It is hetrotrimetric molecule, where each laminin isoform consisting of </li></ul><ul><ul><li>alpha chain. </li></ul></ul><ul><ul><li>Beta chain. </li></ul></ul><ul><ul><li>Gamma chain. </li></ul></ul>
  29. 30. <ul><li>At least 7 different laminin isoforms identified but laminins 1, 5, 6,& 7 are known to occur in DEJ which immunolocalized mainly to L.D. </li></ul><ul><li>By using rotary shadowing technique to allow the electron microscope to visualize the laminin molecule which appear to have an asymmetric cross-like structure ( 1 long arm & 3 short arms). </li></ul><ul><li>The long arm is approximately 125 nm in length & the short arms are variable, but the largest measures approximately 80 nm. </li></ul>
  30. 31. <ul><li>The laminin molecule is divided into:- </li></ul><ul><ul><li>Globular </li></ul></ul><ul><ul><li>Rodlike section </li></ul></ul><ul><li>The 4 extremities of the crosslike structure contain globular domains,& the 3 short arms contain extra domain, approximately 20 nm from their free end. </li></ul><ul><li>The globular & rodlike domains of laminin have been individually implicated in various functions including </li></ul><ul><ul><li>Cell attachment & spreading. </li></ul></ul><ul><ul><li>Aggregation with itself & with other component of the L.D. specially type IV collagen. </li></ul></ul><ul><ul><li>Neurite outgrowth. </li></ul></ul><ul><ul><li>Cellular differentiation. </li></ul></ul>
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  32. 33. Nidogen / Entactin <ul><li>It is a glycoprotein with dumbbell configuration. </li></ul><ul><li>It is attached to one of the short arms of laminin at the gamma 1 chain forming a stable complex. </li></ul><ul><li>Nidogen alone as well as laminin- nidogen complex specifically bind to type IV collagen. </li></ul><ul><li>Nidogen is localized to the L.D. of basement membrane & along the adjacent cell surface of epithelial cell. </li></ul>
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  34. 35. Heparan sulfate proteoglycan <ul><li>HSPG molecules accumulate at cell-matrix interfaces. </li></ul><ul><li>It consists of a core protein of various length with different numbers of covalently associated heparan sulfate chains. </li></ul><ul><li>High sulfate content makes this molecule with highly negative charge & hydrophilic. </li></ul><ul><li>It swell with hydration & have a major role in determining which proteins or ions can transverse the lamina lucida & access the epidermal intracellular spaces . </li></ul>
  35. 36. Epithelial-Specific Basement membrane Components Hemidesmosome Anchoring filaments Epithelial lamina densa Anchoring fibrils & anchoring plaques
  36. 37. Hemidesmosome (HD) <ul><li>It is closely resembles ½ of the desmosome seen in cell – cell junction but based on chemical criteria, these 2 structures appear to be immunologically distinctive. </li></ul><ul><li>Characteristics of HD proteins has been aided by the use of auto-antibodies presented in serum samples of patients with bullous pemphigoid. </li></ul><ul><li>As result of this, the antigens recognized by these sera identified proteins ranging in mass from 165- 240 kDa. </li></ul>
  37. 38. <ul><li>However, there is fair agreement that;- </li></ul><ul><ul><li>230/240-kDa protein the major antigens recognized </li></ul></ul><ul><ul><li>180-kDa protein by these antibodies </li></ul></ul><ul><ul><li>16-kDa protein </li></ul></ul><ul><li>These proteins are immunologically & structurally distinct. </li></ul><ul><li>Monoclonal antibodies have been constructed to both intracellular & extracellular regions of HD. </li></ul>
  38. 39. <ul><li>These monoclonal antibodies identified 3 distinctive proteins </li></ul><ul><ul><li>240-kDa protein </li></ul></ul><ul><ul><li>180-kDa protein </li></ul></ul><ul><ul><li>125-kDa protein </li></ul></ul>
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  40. 41. Major Hemidesmosomal Antigens 240-kDa protein BPAG1 180-kDA protein BPAG2 Plectin Integrin alpha6 beta4
  41. 42. BPAG1 <ul><li>It is a homodimer with homology to desmosomal desmoplakin. </li></ul><ul><li>It is generally believed that it is the major component of the HD inner dense plaque. </li></ul><ul><li>Mutation in BPAG1 EBS </li></ul>
  42. 43. BPAG2 <ul><li>It is an unusual trans-membrane collagen domain. </li></ul><ul><li>It is also called type XVII collagen. </li></ul><ul><li>Its collagenous domain is extra-cellular & its function still unknown. </li></ul><ul><li>Mutation in BPAG2 GABEB </li></ul>
  43. 44. Plectin <ul><li>Previously called HD-1 antigen. </li></ul><ul><li>It is another dimeric desoplakin homologue. </li></ul><ul><li>Its tissue distribution is not limited to DEJ. </li></ul><ul><li>Mutation causing loss of plectin EBS like blisters </li></ul><ul><li>+PMD </li></ul>
  44. 45. Integrin alpha6 beta4 <ul><li>They are large class of trans-membrane extra-cellular matrix binding proteins that provide cell attachment & subsequent signal transduction. </li></ul><ul><li>It has a selective high affinity for laminin 5 & therefore is essential to integration of HD with underlying basement membrane & stroma. </li></ul><ul><li>Mutation in either alpha6 or beta4 chains </li></ul><ul><li>less sever JEB </li></ul>
  45. 46. Anchoring filaments <ul><li>Series of filaments transversing the lamina lucida from the epidermal basal cells &insert into the lamina densa. </li></ul><ul><li>Several antigens now appear to be anchoring filament proteins. </li></ul>
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  47. 48. Major Anchoring filament Antigens Laminin 5 125-kDa 19-DEJ-1 105-kDa Ladinin LAD-1
  48. 49. Laminin 5 (alpha3 beta3 gamma 2) <ul><li>Its general structure as laminin family ( glycoproteins, semirigid & extended structure has an asymmetric cross-like). </li></ul><ul><li>It has short arms comparing to other laminins. </li></ul><ul><li>Its shape is consistent with its potential to be the anchoring filament protein. </li></ul><ul><li>It has a high affinity for integrin alph6 beta4. </li></ul><ul><li>it also bind to the NC-1 domain of type VII collagen ( the anchoring fibril protein). </li></ul>
  49. 50. <ul><li>Mutation in any of its components will lead to loss of its ability to bridge HD & anchoring fibrils resulting in separation within the lamina lucida </li></ul><ul><li>Herlitz JEB </li></ul>
  50. 51. 125-kDa protein <ul><li>It is located at the region where intermediate filaments of basal keratinocyte intersect the HD plaque & at the extra-cellular region. </li></ul>
  51. 52. 19-DEJ-1 antigen <ul><li>It is localized to the region of the lamina lucida beneath the HD. </li></ul><ul><li>? Sulfated ? Proteoglycan. </li></ul><ul><li>Its role in adhesion not fully studied, but supported by if absent JEB </li></ul>
  52. 53. 105-kDa Antigen <ul><li>It is localized in extra-cellular region but closely associated with the cell surface. </li></ul><ul><li>If absent immune-mediated bullous </li></ul><ul><li>dermatoses </li></ul>
  53. 54. Ladinin & LAD-1 <ul><li>Their function unknown. </li></ul><ul><li>Their implication in epithelial adhesion by their identification as ligands for auto-antibodies present in patients with linear IgA bullous dermatosis. </li></ul>
  54. 55. Epithelial Lamina Densa <ul><li>The basement membrane beneath & between HD contains at least alpha1-&alpha2- containing collagen IV molecules. </li></ul><ul><li>It contains laminins, but the exact composition remains in doubt. </li></ul><ul><li>Laminin alpha3- containing molecules are present between HD as well as beneath them. </li></ul><ul><li>However, alpha3 is also contained in two additional epithelial specific namely :- </li></ul><ul><ul><li>Laminin 6 (alpha3,beta1,gamma1) </li></ul></ul><ul><ul><li>Laminin 7 (alpha3,beta2,gamma1) </li></ul></ul>
  55. 56. <ul><li>At DEJ laminin 6 appears to be the major alpha3-containing laminin other than laminin 5. </li></ul><ul><li>Laminin 6 & 7 have the unique property of forming disulfate bounded dimers with laminin 5. </li></ul><ul><li>This laminin 5-6 complex is the major alph3- containing laminin in the lamina densa between HD. </li></ul><ul><li>This complex is a ligand for integrin alpha3 beta1 present between HD, which mediates the binding to the intra-cellular actin cytoskeleton. </li></ul>
  56. 57. <ul><li>If integrin alpha3 beta1 knockout , this will lead to loss of the basement membrane between HDs but not beneath them. </li></ul><ul><li>Laminin 5-6 complex contains gamma 1 chain & can therefore bind to nidogen & type IV collagen network. </li></ul><ul><li>Additional laminins within DEJ found but of minor role including laminin 1. </li></ul><ul><li>Much work remains in LD area which is not fully understood at the molecular level. </li></ul>
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  58. 59. Anchoring fibrils & Anchoring plaques <ul><li>The major component of the anchoring fibril is type VII collagen. </li></ul><ul><li>Type VII collagen appears to have a major triple-helical domain is approximately 450 nm in length. </li></ul><ul><li>Non-triple-helical globular domains exist at the terminal ends of this triple helix,& the N- terminal domain NC-1 is very large & trident-like. </li></ul><ul><li>Type VII collagen is synthesized & secreted as monomeric protein but rapidly dimerizes through disulfate cross-like at the amino terminals. </li></ul><ul><li>These structures are proteolytically cleaved after formation of the centrosymmetric dimer. </li></ul>
  59. 60. <ul><li>The dimers then aggregates laterally to form the anchoring fibrils. </li></ul><ul><li>The complex NC-1 domain binds to laminin 5 & also to components of the lamina densa. </li></ul><ul><li>The helical domain extends perpendicular from the lamina densa & insert into structures termed anchoring plaques. </li></ul><ul><li>The anchoring plaques are electron-dense structure composed of type IV collagen & laminin & possible other components. </li></ul>
  60. 61. <ul><li>They are independent of lamina densa , & distributed randomly in the papillary dermis below lamina densa & are inter-related by additional anchoring filaments. </li></ul><ul><li>Mutation in the gene encoding type VII collagen </li></ul><ul><li>Sever generalized recessive DEB </li></ul><ul><li>To date, all mutation known to underlie both recessive & dominants forms of DEB are due to COL7A1 mutation </li></ul>
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  62. 63. EBS EBS MD EBS GABEB JEB Herlitz JEB Dystrophic EB WWW.SMSO.NET
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  64. 65. <ul><li>Thank You </li></ul>WWW.SMSO.NET